THE CHEMISTRY OF
BREADMAKING
BY
JAMES GKANT, M.SC.TECH., F.I.C., F.C.S.
Head of the Fermentation Industries Department in
the Municipal School of Technology, Manchester ;
Examiner in Chemical Technology in the
Victoria University, Manchester
WITH PLATES
SECOND EDITION
LONDON
EDWARD ARNOLD
1917
All rights reserved
Gc
PREFACE TO THE SECOND EDITION
IN sending out a second edition of this little volume, the
author wishes to express his acknowledgments of the very
kindly reception accorded to the first.
He has corrected a few errors which occurred in the
original volume, and has added some pages at the end of
this book in the form of addenda, hoping thereby to
increase its efficiency.
The author would strongly advocate more strenuous
efforts on the part of all bakery students to persevere in
the pursuit of scientific knowledge to a much greater
extent than hitherto, in order to become more successful
in their business, and endeavour to place the trade on a
higher level than it at present occupies.
J. G.
MANCHESTER, November 1916.
The Reference Numbers 1-14 in the text are to the ' Addenda'
on pp. 219 et seq.
PREFACE
*
THIS volume, on the application of science to the very
important industry of Breadmaking, is put forward in
the hope that it may fill in a gap which undoubtedly
exists in the literature and text-books on this subject.
It does not lay claim to any literary merit, but should
rather be looked upon as an honest endeavour to assist
learners who are groping in some amount of obscurity
or darkness, with the dawn only just beginning to break.
The majority of earnest students in breadmaking
and there are many have not the same opportunities
that are enjoyed by their fellows in other industries,
in most of which there is a plethora of books, many of a
very excellent character. For books the breadmaking
industry at the moment is dependent upon the efforts of
Mr. William Jago of Brighton, and Mr. John Kirkland
of the School of Baking and Confectionery in the London
Borough Polytechnic, in addition, of course, to several
useful trade papers. This book is not intended to be
a text-book on either chemistry or physics, but rather on
the application of these and the kindred science of
technical mycology to the subject of Breadmaking. It
is advised that all who study its contents should do so in
conjunction with some simple text-books on chemistry,
physics, mechanics, and the elements of biology and
botany.
Recourse has been had in a few instances to chemical
equations, and whenever they have been used, the names
vi CHEMISTRY OF BREADMAKING
of all substances taking part in the reactions have been
inserted immediately below. As years advance, and a
scientific education is given to the members of the trade
generally, such an arrangement will become as unneces-
sary as it is in many other technical sciences dependent
on a working knowledge of chemistry.
A large number of analytical figures are included in
the little volume, which are quite original, and have not
before been published. In other instances the sources
of the information have been acknowledged. This has
been considered advisable for reference sake, as very few
of such exist to assist the student in his analytical studies.
If the book merits and receives the favourable con-
sideration of the trade and allied industries, it is hoped
that in future editions any imperfections may be eradi-
cated, whilst its scope and usefulness may be greatly
enlarged.
The author's thanks are due to his colleagues, Messrs.
F. G. Richards, F.C.S., and Abraham Flatters, F.R.M.S.,
to the former for assistance in analytical work and proof-
reading, and to the latter for kindly help in preparing
many of the illustrations ; also to his student, Mr. F.
Robinson, B.Sc. Tech., for aid in the illustrations for the
technical mycology portion of the work.
J. G.
MANCHESTER.
CONTENTS
CHAP. PAOB
I. INTRODUCTORY ... .... 1
II. THE ATMOSPHERE. WATER 10
III. ACIDS, ALKALIES AND SALTS 22
IV. BAKERY PHYSICS : THERMOMETERS, BATIOMTCTERS, AND
CALCULATIONS 30
V. HEAT AND PHYSICAL PROBLEMS 42
VI. THE ORGANIC CONSTITUENTS OF THE CEREALS . . 55
VII. THE CEREALS AND THEIR COMPOSITION ... 91
VIII. MILLING, MEALS, FLOURS, MALTS AND EXTRACTS . . 102
IX. FERMENTS, YEASTS, MOULDS, BACTERIA AND BARMS . 125
X. BREADMAKING PROCESSES AND BREADS . . . 153
XI. ANTISEPTICS AND BAKEHOUSE HYGIENE . , . 172
XII. FUELS AND OVENS 178
XIII. THE ANALYSIS OF CEREAL FOODS .... 186
BIBLIOGRAPHY ......... 217
ADDENDA ....,.... 219
INDEX .... . 225
LIST OF PLATES
I. STARCHES at page 72
II. STARCHES ,,73
III. (i.) WHEAT FLOWER, (ii. ) SECTION OF WHEAT BERRY 92
IV. (i.) SECTION or A WHEAT ENDOSPERM, (ii.) SECTION
THROUGH ALEURONE CELLS, (iii.) SECTION OF
WHEAT GERM
CHEMISTRY OF BREADMAKING
CHAPTER I
INTRODUCTORY
BREADMAKING and the kindred fermentation industry of
brewing have been known and practised from the remotest
ages of mankind. Long ages before the Christian era, the
growing of wheat and other cereals, the preparation of the
grain for the mill, the milling of the cleaned and prepared
grain, and the conversion of the meal into cakes or bread
both leavened and unleavened, have occupied the attention
of mankind. To the German, French, and English ex-
plorers of the ruins of ancient Troy we are indebted for
accounts of the wheat and barley growing in those early
times and the certain knowledge that these cereals were used
for the preparation of foods. The pyramids of Egypt, the
mound tombs in North Africa and Asia, and the lake
dwellings of Switzerland have all furnished evidence of the
uses of wheat and barley, as the starting points for making
bread and fermented liquids for the inhabitants of those
ancient places. In the early chapters of the book of Genesis,
an interesting account is given of the proclivities of one of
the earliest Hebrews in making a corner in corn, and
afterwards in selling the corn from his granaries to the
famine-stricken nations around Egypt at enhanced prices.
Early Greek and Roman writers appear to have been
intimately acquainted with both breadmaking and brew-
ing. For example, the elder Pliny in his writings makes a
statement to the effect that flour yielded one and a third
times its weight of bread.
A
2 CHEMISTRY OF BREADMAKING
In our own country, the Anglo-Saxons were adepts in
the art of making cakes and mead. In all cases, in these
early times, the word ' flour ' refers to meal, and this was
produced by crushing the wheat in hand-stone mills or
' querns.'
The evolution of the present-day white loaf has been a
question of time like that of any other important industry,
and to trace it step by step would be a study of considerable
interest, but entirely outside the scope of this work.
In order to produce bread of great food value, a loaf
pleasing to the sight, palatable, easy of digestion and
assimilation, and, above all, 4 composed of three out of the
four proximate principles of foods, is a work requiring
much skill and manipulative power in addition to a general
knowledge of flours and other raw materials. This implies
that the modern, scientific baker should possess a working
knowledge of such sciences as those of chemistry, physics,
biology, botany, mechanics, and mathematics.
Chemistry is that branch of physical science which has
for its chief object the study of the composition of matter.
For convenience sake the study of chemistry is divided into
two parts inorganic and organic. The former deals with
the forms of matter known as the non-metals or metalloids
and the metallic bodies, together with the derivatives of
both ; organic chemistry has for its object the consideration
of the carbon compounds and their derivatives. The same
laws of combination, the same forces and all other influences
affect the compounds of both groups equally, but as there
are so many thousands of the carbon bodies it is better to
consider them separately.
Matter is made up of almost infinitely small particles,
the atoms and molecules. An atom is generally defined to
be the smallest quantity of matter that can enter into
chemical combination and can rarely exist in the free state ;
whilst a molecule is composed of two or more atoms and is
the smallest quantity of matter that can exist in the free
state. Matter under different conditions of temperature
and pressure exists in three states : gaseous, liquid, and
INTRODUCTORY 3
solid. Each of these three may be either elementary or
compound matter.
An element or elementary matter is that which is composed
of particles all of the same kind, as, for example, sulphur,
iron, oxygen, etc., while a compound or chemical compound
is composed of two or more elements in a state of chemical
combination, as, for example, water, sugar, butyrin,
gypsum, etc.
At the present time there are about eighty so-called
elements recognised, but this number is not by any means
a fixed one, for almost every year fresh additions are made
to the list. The elements are divided into two groups :
the non-metals or metalloids, and the metals.
The metals are characterised by possessing some of the
following properties :
They possess a bright shining surface or lustre when seen
in the lump ; they are of high specific gravity or are said
to be dense compared with the non-metals ; are good
conductors of heat and electricity ; possess ductility,
malleability and tenacity ; form alloys or mixtures of
metals which contain not only the properties of the con-
stituent metals as enumerated above, but in addition
certain special ones ; and in most cases they have a char-
acteristic appearance or fracture when broken across or torn
apart. All the known metals, with the single exception of
mercury a bright, very heavy, shining liquid exist in
the solid state.
Non-metals rarely possess any of the above properties,
except a few of the solid ones such as sulphur, phosphorus,
silicon, and arsenic, which approximate somewhat closely
to the metals in a few of their properties. The metalloids,
with the exception of bromine a dark, heavy, reddish-
brown, strongly smelling liquid exist either as gases like
hydrogen, oxygen, nitrogen, chlorine, etc., or as solids, for
example, as carbon, iodine, boron, selenium, tellurium, and
the four previously mentioned non-metals.
All the gaseous bodies, whether elementary or compound,
conform to all the laws affecting gases, viz., those concerning
4 CHEMISTRY OF BREADMAKING
the relation between volume and pressure, those of com-
bination, diffusion, and so forth.
The important laws of chemical combination are :
(1) The law of combination in fixed and definite propor-
tions by weight.
(2) The law of multiple proportions.
(3) The law of reciprocal proportions.
To these laws of combination is attached the name of the
Manchester chemist John Dalton who attempted to
explain them by his Theory of Atoms.
The law of the Conservation of Matter, allied to that of
the conservation of energy, points out that the sum of
matter in the universe is fixed and unalterable. Matter can
neither be created nor destroyed ; all that is possible is to
change its form. Chemical force, or the force of chemical
affinity, tends to produce a permanent change in the form
of matter, while physical forces tend to produce only a
temporary change. For example, if cream of tartar and
bicarbonate of soda, both perfectly dry, are ground together
in a mortar, there has been formed simply a mixture of the
two compounds, just as when sand and sugar are intimately
mixed ; but if the molecules of the two compounds are by
any means brought so close that they actually touch, as,
for example, when water is brought into them, then chemical
combination ensues forming the new compounds, Rochelle
salt, and carbonic acid gas (C0 2 ).
A chemical equation is an expression of the law of
conservation of matter, for the sum of the substances taking
part in the reaction is equal to the sum of the products
obtained. These equations are usually expressed by
symbols, which will now be explained.
The names of all the elements are expressed by a letter
or letters, something like a form of shorthand. Similarly,
the compounds are represented by bringing the symbols
standing for the constituent elements close together.
The symbols also represent the relative weights of the
atoms, or the relative quantities by weight which enter into
chemical combination.
INTRODUCTORY
The more common non-metals and metals, their symbols,
atomic weights and states of matter, are given in the table :
NON-METALS.
METALS.
Name.
Symbol.
At. m.
State.
Name.
Symbol.
At. Wt.
State.
Argon
A
39-88
Gas
Aluminiiun
Al
27-10
Solid
Arsenic
As
74-96
Solid
Calcium
Ca
40-09
Bromine
Br
79-92
Liquid
Copper
Cu
63-57
Carbon
C
12-00
Solid
Gold
Au
197-20
Chlorine
Cl
35-46
Gas
Iron
Fe
55-85
Fluorine
F
19-00
Gas
Lead
Pb
207-10
Hydrogen
H
1-008
Gas
Magnesium
Mg
24-32
Iodine
I
126-92
Solid
Mercury
Hg
200-00
L quid
Nitrogen
N
14-01
Gas
Potassium
K
39-10
Solid
Oxygen
16-00
Gas
Sodium
Na
23-00
Phosphorus
P
31-04
Solid
Tin
Sn
119-00
Sulphur
s
32-07
Solid
Zinc
Zn
65-37
All chemical reactions may be expressed by equations.
The bodies taking part in the reaction are placed on the
left-hand side of a sign of equality =, whilst the products
formed go on the right side of the sign. Example.
When silver nitrate solution is brought into a sample of
water containing common salt, silver chloride a white
curdy compound insoluble in the liquid and sodium
nitrate are formed.
This may be expressed in the following way :
AgN0 3 + NaCl = AgCl + NaNO 3
Silver Sodium Silver Sodium
Nitrate Chloride Chloride Nitrate
(107-88 + 14-01 + 16x3) + (23 + 35-46) - (107-88 + 35-46) + (23 + 14-01 + 48)
169-89 + 5846 = 143-34 -f 85-01
228-35 228-35
It is the usual custom to write down the symbols as shown
without the figures, which are here used to prove that the
compounds taking part in the reaction are equal in weight
to the products obtained.
Another example is as follows :
Carbon dioxide gas, employed in the aerated water
6 CHEMISTRY OF BREADMAKING
industry, is prepared by decomposing pieces of marble
with sulphuric acid.
CaC0 3 + H 2 S0 4 = C0 2 + CaS0 4 + H 2 O
Marble or + Sulphuric = Carbon + Calcium + Water
Carbonate acid dioxide sulphate
of lime
The sources of the non-metals and metals. Many of the
non-metals exist in the free state in nature, e.g. argon,
nitrogen, and oxygen in the atmosphere ; most of the
remainder, owing to their active chemical properties, are
found in a state of combination with one or more elements
in which combination they form the acidic group, as
chlorides, bromides, sulphides, fluorides, phosphates,
carbonates, sulphates, and others.
A number of the lighter metals exist wholly in the
combined state with the acidic groups of the metalloids,
the metals taking the part of the base. Many of the
heavy metals exist in the free state.
The combinations of the metals with the non-metals as
existent in the solid crust of the earth give rise to a large
number of important industries.
Aluminium is a typical instance of this. It exists in
combination with oxygen and with oxygen and water.
The oxide, corundum or emery, is used in the grindery and
polishing trades. The combination with oxygen and water
is known as bauxite or tfie, hydrated oxide of aluminium,
a body largely employed in the extraction of the metal
itself, in the preparation of alums, aluminium sulphate,
alumino-ferric, and in the manufacture of the artificial
ultramarines. The ultramarines are used for whitening
low grades of sugars, as the blue bag in laundries and by
confectioners, for staining paper, etc. The clays are
double silicates of aluminium ; these are the starting points
of the china, earthenware goods, and coarse red pottery
industries. Asbestos is another mineral of the double
silicate aluminium group, giving rise to a wide range of
employment.
Calcium is another metal which in its combinations as
INTRODUCTORY 7
existing in nature gives rise to a large number of industries.
It is only necessary to call to mind marble, limestone, chalk,
pearls (all various forms of carbonate of calcium), or the
sulphate as gypsum and selenite, or the apatites and other
phosphates of lime, to see in the mind's eye a wonderful
vista of industries ; but enough has been written to show
the value of a good general knowledge of chemistry.
Physics is a branch of natural science which has for its
consideration the effects of force on matter. Like the
science of chemistry it is studied for the sake of convenience
under a number of divisions, as pure and applied physics ;
also under the terms light, sound, heat, magnetism and
electricity. Of these, light, heat, and electricity are of much
importance to the baker ; for example, a knowledge of
light and optics is helpful in microscopy and polarimetry ;
electricity is used as a motive power and for lighting
purposed ; heat is an all-important subject affecting
practically every branch of a baker's work. Each of these
three branches of physical science will be considered in its
proper place.
At this point it is only necessary to draw attention to
the part taken by heat in assisting to bring about and
hasten chemical reactions. One of the chief effects of heat
on the different forms of matter is to expand it in all its
dimensions, and when the source of heat is withdrawn most
bodies contract again to their original form and size,
demonstrating that a physical force tends to produce a
temporary change in the form of matter. But heat also
causes the force, chemical affinity, to act ; as previously
pointed out, chemical action does not take place except
when the reacting particles are in actual contact. Heat
when applied expands the particles until they do actually
touch, then the force of chemical affinity acts and causes a
combination of the particles, thus forming a new compound
or compounds. For instance, some powdered iron and
flowers of sulphur are ground together in a mortar, yielding
a greenish-yellow mechanical mixture, the component parts
of which may be readily separated either by using a magnet
8 CHEMISTRY OF BREADMAKING
to withdraw the iron powder, or by shaking up the mixture
with water, in which case the iron particles owing to their
greater density fall to the bottom of the water while the
sulphur remains on the surface. If, however, a portion of
the mixture is gently heated, the particles first expand,
then the sulphur melts ; actual contact now takes place,
and a new body is formed which is of a permanent character.
The equation representing this reaction is as follows :
Fe+ S = FeS
Iron + Sulphur = Sulphide of iron
That FeS is a different body from the mixture of iron and
sulphur may be demonstrated by bringing a few drops of
acid on each. With the iron sulphide the nauseous-
smelling sulphuretted hydrogen and a salt of iron will be
obtained ;
FeS + H 2 S0 4 = H 2 S + FeS0 4
Iron v ., . , _ Sulphuretted Iron
sulphide 4 " hydrogen + sulphate
In the case of the mixture :
Fe + S -f H 2 S0 4 = H 2 + FeS0 4 + S
Iron + Sulphur + Vitriol = Hydrogen + Iron sulphate + Sulphur
Biology is another of the physical sciences, which, on
the one hand, is closely associated with botany, or the
science dealing with the members of the vegetable kingdom,
and, on the other, with zoology, the science that treats of
animal life. With this latter the baker is not directly
concerned ; but that portion of biology which has for its
object the consideration of life-action is of especial import-
ance to him as it helps him to understand the part played
by vital functions in fermentation. Without yeasts and
barms the baker would be unable to place before the
general public the wholesome, palatable product that
appears on the table at every meal ; hence the baker is
compelled to give some slight attention to biology.
Nor has he time to neglect botany, which takes into
consideration all that concerns the wheat and other
cereals from which the daily carbohydrate food of the
INTRODUCTORY ,
9
>'>>> JL * > j > >
people is prepared. Everything that tends to improve
wheat, so that flours better in all their properties are milled
from it, is of the utmost interest to the trade. Moreover,
a baker must not forget that division of botany, known as
the Cryptogamia, for it has the group of microscopic fungi
as one part of its many members. Unless he knows
something of moulds and bacteria, his bread, flour, and
cakes may suffer from this lack of knowledge.
In the modern machine bakery the master or bakery
manager must understand something of mathematics and
the sister science of applied mathematics or mechanics.
These sciences deal with the construction and arrangement
of machines, their speeds of running, gearing, pulleys, and
all else that affects the driving mechanism. Add to this
a good general knowledge of steam, then the master baker
and his manager are in some ways fitted to cope with the
things that come into the daily life of a baker. There is
scarcely an industry of any importance that requires so
much general information on the part of those engaged in
it as that of breadmaking.
The commercial side of the business does not come
within the scope of this or any book. Book-learning may
assist it in some slight degree, but there is nothing like being
deeply engaged in it to stimulate one's energies to make an
effort to grasp this part of the many-sidedness of a baker's
life.
CHAPTER n
THE ATMOSPHERE. WATER
THE word ' atmosphere ' is derived from two Greek ones,
atmos, vapour, and sphaira, a sphere or globe. It is the
name given to the gaseous elastic fluid which envelops the
earth's globe to a depth of about two hundred miles and
exerts a pressure of 14-73 Ibs. on every square inch, or
1033 grams per square centimetre of surface. The tempera-
ture as well as the density of this envelope decreases with
increase of height from the earth's surface, and therefore
the pressure also diminishes. For example, one volume
of air at the sea-level expands to two volumes at slightly
over half a mile in height ; at a height of a mile and three-
quarters it has expanded to eight volumes ; while at three
and a half miles it has become sixty-four volumes.
Previous to the Christian era it was known that air
possessed weight. This was confirmed by Galileo in A.D.
1640 and by Torricelli and Pascal in 1643. One litre (1-76
English pints) of dry air in the latitude of Paris weighs
1-2934 grams, in London 1-29318 grams, and in Manchester
1-293 grams.
In the seventeenth century Hooke and Mayow pointed
out that the atmosphere contained at least tAvo substances,
one that aided combustion now known as oxygen while
the other nitrogen did not. In its chemical composition
the air is a mixture of gases which varies according to
position and circumstances ; thus, normally it contains
20-833 per cent, of oxygen and 79-167 per cent, of nitrogen,
both by volume ; or approximately every five volumes of
air consist of one volume of oxygen and four of nitrogen.
The composition by weight of pure, dry air is 23-005 per
cent, of oxygen and 76-995 of nitrogen.
10
THE ATMOSPHERE 11
In addition to the foregoing elements, ordinary air
contains carbon dioxide, water vapour, ammonia and its
salts, traces of ozone, nitric acid and other bodies. Associ-
ated with the nitrogen are the so-called nitrogen gases
argon, helium, krypton, and neon.
The atmosphere of towns contains numbers of impurities
which differ somewhat with the trades established in the
area ; thus, sulphur dioxide and trioxide, particles of sooty
matter, white arsenic, hydrochloric acid, etc., may be found.
A large number of researches show that the composition of
ordinary pure air is not by any means constant ; for ex-
ample, in various parts of the northern hemisphere the
quantity of oxygen by volume averages 20-95 per cent.,
on high mountains about 20-94 per cent., in the Polar
regions 20-90 per cent., and in crowded rooms and buildings
from 20-22 to 20-45 per cent. During the dense fogs
which often prevail in large towns, it has frequently been
demonstrated that the amount of oxygen is much below
the normal, while that of the carbon dioxide is augmented.
This latter gas like water vapour may be looked upon as
a regular constituent of the atmosphere, and like water
vapour its quantity is variable. Black of Edinburgh in
the eighteenth century was the first to prove its presence
in air, and he recognised it as being the same gas as that
which is set free in the burning of limestone and chalk.
He further showed that carbon dioxide gas converted
caustic alkalies into mild alkalies or alkaline carbonates.
The normal amount in the air is from three to four volumes
per ten thousand. In thickly populous areas this quantity
is often doubled and trebled ; in crowded rooms or public
conveyances the quantity rises to an objectionable amount,
as, for example, was formerly the case in London Under-
ground Tube stations. Mr. D. A. Sutherland in 1902 showed
that the carbon dioxide during morning and evening heavy
traffic was from 11-0 to 20-46 volumes per ten thousand of
Tube air. Anything above eight parts per ten thousand of
air should be looked upon as deleterious to animal life,
especially when accompanied by the noxious exhalations
12
CHEMISTRY OF BREADMAKING
from the lungs of persons suffering from consumption and
other pulmonary diseases. A table of comparison between
the composition of ordinary and respired air is added :
Constituents.
Ordinary air.
Respired air.
Nitrogen,
Oxygen,
Carbon dioxide, .
79-03 per cent.
20-94
0-03
79-03 per cent.
16-99
3-98
Carbon dioxide passes into the atmosphere from the
following and other sources :
The respiration of animals and certain plants.
The decay of organic matter.
The combustion of coal, coke, wood, and other carbon-
aceous bodies.
From subterranean causes.
Its presence and approximately a rough idea of any
excess may be shown by the rapidity with which a film of
calcium carbonate forms on a surface of clear, fresh lime
water exposed in a soup-plate to the atmosphere. The
physical processes of diffusion distribute this gas through
the constituents of the air, while its amount in country
districts is kept normal by the action of vegetation in assimi-
lating it with the help of moisture, chlorophyll and sun-
light ; and also by the rain in all districts, which dissolves
it and carries it down into the earth or into the streams.
Ammonia 1 and its compounds exist in air to the extent of
less than one per cent. Ozone, hydrogen peroxide, and
nitric acid occur only in mere traces or not at all. Hayhurst
and others have proved by means of kites that in the upper
atmosphere, from five to thirteen miles, none of the three
last-mentioned compounds occur.
Aqueous or water vapour is the most variable constituent,
as its quantity changes with the degree of saturation,
temperature and character of the earth's surface. In the
THE ATMOSPHERE 13
British Isles, air at 32 F. (0 C.) contains less than
one per cent, by volume, but at 60 Fah. rather more ;
while in tropipal land areas it is fully four times as much.
At ordinary temperatures in a room an adult person
respires about two- thirds of an ounce of water per hour.
Its presence may readily be detected by placing some ice
in a glass of water and noting the condensation of moisture
or dew on the outside of the glass ; or it may be observed by
exposing on a plate dry caustic soda, which quickly becomes
moist in the air owing to the absorption of the water vapour.
The relative humidity 2 or degree of moisture for house
temperatures should lie between 64 and 72 per cent.
It will be seen from the foregoing statements that the
atmosphere is composed of a mixture of elementary and
compound gases together with some solid floating particles,
all of which vary slightly in. amount according to the pre-
vailing circumstances.
The atmosphere over thickly-populated land areas con-
tains countless myriads of very minute forms of plant life
known as the micro-organisms, the most important and
widely distributed of which are the ubiquitous bacteria.
Many groups of these exercise a beneficent influence over
animal life, but others, especially the pathogenic or disease-
producing groups, have a destructive effect.
In concluding this chapter on the air it is advisable to
emphasise the important part played by oxygen in killing
disease and filth germs, in oxidising poisonous organic
matter from animal and vegetable sources, and in its
purifying action on rivers, vegetable and animal life ;
it. is also the chief agent in all combustions.
The average composition of a thousand volumes of air
may be approximately summarised as under :
Nitrogen and its gases, . . 779 volumes.
Oxygen, . . . . . 207
Water vapour, .... 13
Carbon dioxide, ammonia and its I ,
compounds, sooty particles, etc. j "
14 CHEMISTRY OF BREADMAKING
During recent years the gases of the atmosphere have
been liquefied by the compression, cooling, and expansion
principle of Hampson and Linde. The liquid air is homo-
geneous, of faint blue colour, and extremely cold. It may
best be preserved for a short time in silver-coated, double
flasks, the space between the two being rendered as vacuous
as possible.
WATER
Pure water is a chemical compound formed by the
combination of the two gases, hydrogen and oxygen, as, for
example, when hydrogen is burned either in oxygen, or in
air which contains the latter gas. The natural waters occur
in the oceans, seas, lakes, rivers, streams, subterranean
waters and springs, and in the clouds as aqueous vapour.
All such natural waters contain gases, liquids, and solids
dissolved in them. Some of these are looked upon as
impurities, whilst others are necessary ingredients of a
drinking water.
The che'mical composition of water may be determined
either volumetrically or gravimetrically, i.e. either by the
relative volumes or relative weights of its constituents.
The composition by volume was shown by Humboldt,
Gay-Lussac, and others to be two volumes of hydrogen
combined with one of oxygen to form water. The reverse
reaction may be carried out by electrolysing water, in which
case it is split up into two volumes of hydrogen and one of
oxygen. A little later in the nineteenth century, Berzelius,
Dulong, Dumas, and Stas, worked out the composition by
weight, and established the fact that 11-136 parts by weight
of hydrogen combine with 88-864 parts of oxygen to form
a hundred parts of water ; or, water contains one-ninth of
its weight of hydrogen, and eight-ninths of oxygen.
Pure water is a clear, tasteless, odourless liquid, which,
when seen in bulk, possesses a pale greenish-blue colour.
It is a poor conductor of heat and electricity, and is almost
incompressible. One cubic centimetre at 4 C. weighs one
WATER 15
gram, and one pint, which consists of twenty ounces, weighs
one and a quarter pounds, so that a gallon weighs ten
pounds avoirdupois.
Water, according to the temperature and pressure,
exists in the three states of matter, solid, liquid, and gase-
ous. Thus, if the temperature is at C. (32 F.) or
lower, water exists in the forms of ice and snow. Between
and 100 C. (212 F.) it is a liquid. At temperatures
above 100 C. it becomes a gas or vapour.
In order to change it from the solid to the liquid state,
heat is required, and as this cannot be registered by a
thermometer, it is spoken of as ' latent ' or hidden heat.
Similarly, in passing from the liquid to the gaseous state,
about seven times as much heat is necessary. Latent heat
is defined to be the quantity of heat required to bring about
a change of state in the matter without a rise of its tempera-
ture. Thus, if it is desired to convert one pound of water
at 212 Fah. into steam at the same temperature, 967
British heat units must be brought into the water. On
the other hand, when steam is condensed to water, the same
quantity of heat is evolved. Use is made of this property
to raise quickly the temperature of cold water, other liquids,
and mixtures of liquids and solids.
It is both useful and instructive to study the change
of volume in water as it is gradually heated from 32
to 212 F. From 32 a given volume of water continu-
ously contracts until it reaches 39-2 F. At this point
it is denser than at any other temperature. One cubic
centimetre (1 c.c.) at .32 weighs 0-99987 grams, while at
39-2 the same volume weighs exactly one gram. This
is said to be * the point of maximum density for water.'
From 39-2 towards 212 the volume continuously expands,
and consequently becomes less dense. One volume of
water at 212 F. yields 1696 volumes of steam. The
specific gravity (sp. gr.) of steam, or its density compared
with hydrogen, is 9-0, but compared with air, it is
Q. 00
=0-622. (Air is 1445 times denser than hydrogen.)
14-45
16 CHEMISTRY OF BREADMAKING
When water is converted into ice an expansion takes place,
100 volumes of water becoming 107 volumes of ice. The
sp. gr. of ice compared with water is ig-= 0-9436, which
accounts for ice floating on the surface of water. Pure dis-
tilled water at 39-2, or more generally at 60 F., for the sake
of convenience is taken as the standard of comparison for
the relative density or sp. gr. of liquids and solids.
Among the more important properties of water is its
great solvent power. It is spoken of as the almost universal
solvent.
By solvent power is meant the property that water and
other liquids possess of overcoming the force of cohesion
which binds the particles of solids together, or of being
miscible with other liquids. A very large number of sub-
stances when shaken up with water rapidly disappear or
are said to be dissolved. Most of these are more readily
soluble in hot than in cold water. For example, 100 parts
by weight of water at 32 F. dissolve 13-3 parts of nitre
or potassium saltpetre. At 122 F. 86 parts are soluble,
while 247 parts dissolve at 212 F.
Gypsum or calcium sulphate is an exception. This salt
is less soluble in boiling than in cold water. Sodium
chloride or common salt is almost as soluble in cold as in
hot water. Gases, on the other hand, are less soluble in
hot than in cold liquids.
Owing to its solvent powers the water that exists in
nature invariably contains substances in solution. It
often also has floating particles or substances in suspen-
sion. These latter settle out or may be removed by
filtration.
The substances in solution vary in different localities
according to the rock formations, soils, manuring of the
land, and other causes. The presence on the land of cattle
and sheep, the manuring and the decaying of vegetable
matters and other refuse are causes of organic impurities
in a water supply. The weathering of rocks introduces
mineral matters that are responsible for the hardness of a
water.
WATER 17
Some of these mineral salts, such as common salt and
gypsum, possess antiseptic properties. When present in
excessive quantities these check the fermentative action of
the yeast. This is noticeable in the waters of the great
Cheshire plain which come from the New Red Sand-
stone rocks, and also in the Burton waters, which
owe their origin to the Keuper beds in that district.
Frequently the smaller towns and villages on the sea-
coast, in which the water supply is drawn from wells,
are troubled by the brackish character of the water.
Mablethorpe on the Lincolnshire coast is an interesting
case in point.
Water fit for drinking and for the manufacture of food-
stuffs like bread and confectionery goods should be free
from organic impurities and at the same time not too hard.
Organic impurity may be destroyed by exposing the water
freely to the air, either by passing it down a series of stone
steps, by filtering it through specially devised filter-beds,
by running it in a shallow broad sheet over sills, or by a
combination of these methods. This exposure to plenty of
light and air has also the effect of considerably diminishing
the bacterial content of a water. If a water is excessively
hard, as, for example, the supplies from limestone and
chalk areas, it may be softened by heating it so as to
decompose the bicarbonates of lime and magnesia, then
filtering or allowing to settle ; or by mixing suitable
chemicals with the water and then filtering, or settling.
For example, a Derbyshire water may readily be softened
by the addition of milk of lime in the proper proportions
and allowing the treated water to settle. Another common
reagent for the purpose, suitable for many waters, is
ordinary soda-ash, a crude dry form of carbonate of
soda. On a small scale for washing and domestic uses,
except for cooking, both soap and borax will be found
useful.
It should be remembered that very soft pure waters,
as well as those of an acid character, readily attack and
dissolve lead, and then become highly poisonous. Such
18 CHEMISTRY OF BEEADMAKING
waters must not be conveyed by means of leaden pipes.
Other poisonous bodies liable to occur in the natural waters
are salts of iron and copper.
The following is a useful classification of waters :
(1) Alkaline waters, in which the chief salts in solution are
the compounds of sodium and potassium.
(2) Calcareous waters, the chief salts present being bicar-
bonates of lime and magnesia.
(3) Saline waters. These are of two types : (a) brackish,
(6) gypsum. The latter contain chiefly sul-
phates of lime and magnesia, while the brackish
waters contain excessive quantities of common
salt.
(4) Siliceous waters. These are generally very soft pure
types of water, and hence eminently suitable for all
domestic purposes.
(5) Waters of no special type, in which there are no
predominating salts.
Examples of some typical waters.
(1) Manchester tap water.
Calcium sulphate (CaS0 4 ), . 1-728 grains per gallon.
Magnesium sulphate (MgSO 4 ), . 0-587 ,, ,,
Magnesium chloride (MgCl 2 ), . 0-513 ,, ,,
Sodium chloride (NaCl), . . 0491
Oxides of iron, alumina, silica, . 0*252 ,,
Organic matter including traces } ~ 7 _,
of nitrites and nitrates, .
Total solids, 4-345
Total hardness 2, all of which is permanent.
The Manchester water supply is a good example of a
WATER 19
pure soft siliceous water suitable for domestic, breadmaking,
and boiler-feed purposes.
(2) A Burton brewing well water.
Calcium sulphate (CaS0 4 ), . 22-968 grains per gallon.
Magnesium sulphate (MgSOJ, . 8-895 ,,
Potassium sulphate (K 2 S0 4 ), . 6-672
Calcium carbonate (CaC0 3 ), . 11-065
Magnesium carbonate (MgC0 3 ), 2-757 ,,
Sodium chloride (NaCl), . . 9-09-1
Potassium chloride (KC1), . 1-874
Iron carbonate (FeC0 3 ), . . 0-573 ,,
Silica (Si0 2 ), .... 0-691
Organic matter, . . . traces
Total solids, 64-589
A typical hard water from the Keuper Marls, well suited
for brewing pale ales, and malting purposes.
(3) A calcareous water from a London chalk well (Steel).
Calcium carbonate (CaC0 3 ), . 18-88 grains per gallon.
Magnesium carbonate (MgC0 3 ), . 0-28 ,, ,,
Sodium chloride (NaCl), . . 1-94 ,,
Sodium sulphate (Na 2 SO 4 ), . . 0-74
Potassium silicate (K 2 SiO 3 ), . 0-65
Potassium sulphate (K 2 SO 4 ), . 0-38 ,,
Potassium carbonate (K 2 C0 3 ), . 0-26
Silica (Si0 2 ), . . ' . . 0-69
Organic matter, .... 0-73
Total solids, 24-55
20 CHEMISTRY OF BREADMAKING
(4) An Edinburgh water of no particular type (Steel).
Calcium sulphate (CaSO 4 ), . .11-69 grains per gallon.
Magnesium sulphate (MgS0 4 ), .'10-90 ,, ,,
Sodium sulphate (Na 2 S0 4 ), . 4-46
Calcium carbonate (CaC0 3 ), . 19-86
Magnesium carbonate (MgCO 3 ) ,. 5-48 ,, ,,
Sodium chloride (NaCl), . .11-71
Potassium chloride (KC1), . . 2-86
Silica (Si0 2 ), .... 0-08
Organic matter, . . . . 1-56
Total solids, 69-20
Both the above waters are suitable for brewing and
malting, but not for other purposes without careful softening
treatment.
Mineral waters are useless either for domestic or bread-
making purposes. Medicinally, however, they are of
considerable value.
The more important English mineral springs are those
of : Epsom, containing magnesium sulphate or Epsom salts ;
Tunbridge Wells, which are chalybeate or iron waters ;
Cheltenham, containing Glauber's salt or sodium sulphate ;
Droitwich and Nantwich, famous for their brine baths ;
Buxton, Bath, and Leamington, which are mixed mineral
waters ; Harrogate, where there are two classes, the one
containing sulphuretted hydrogen gas and mixed mineral
salts, and the other mixed mineral salts alone.
The effect of waters of different classes in baking. This
question must be considered from the hygienic point of
view, and also from that of the action of the mineral salts
existing in the waters.
Pure, wholesome bread cannot be made from water
contaminated either with sewage or decomposing vegetable
matter ; hence water in a bakery must be free from all
forms of organic impurity. Soft and alkaline waters
WATER 21
possess great extractive properties ; in addition they affect
the protein constituents as gluten and permit of its being
more readily modified and degraded. Hard waters,
especially of a gypsum type, have an entirely opposite or
retarding effect. Moreover, very strongly impregnated
gypsum waters check the action of yeast by the antiseptic
properties of this salt. Gypsum has also a general binding
influence on flour, following in this the action of sulphates
generally, and further causes bread after cutting to quickly
become dry. This is very noticeable in the case of prize
loaves at exhibitions, in which sulphate of lime has been
employed as an improver of the texture
CHAPTER III
ACIDS, ALKALIES, AND SALTS
THESE three groups of substances exist in the three states
of matter, viz., gaseous, liquid, and solid.
ACIDS
The word ' acid ' takes its origin from ' acetous,' the name
primarily given to the sour-tasting liquid obtained by
exposing weak alcoholic wines to the atmosphere.
Acids possess most of the following properties,: A sour
or acid taste, resembling that of vinegar. The pOAver of
changing the vegetable dye litmus from blue to a red shade
of colour. The neutralising of alkalies with the formation
of salts and water, and the power of dissolving some of the
more common metals, metallic oxides, hydrates, and
carbonates.
Acids are classified as :
(1) Mineral acids, or those which are prepared from
minerals, as
Hydrochloric acid or ' spirits of salt ' (HC1) ;
Nitric acid or ' aqua fortis ' (HN0 3 ) ;
Sulphuric acid or ' vitriol ' (H 2 S0 4 ) ;
Sulphurous acid (H 2 S0 3 ) ;
Carbonic acid (H 2 C0 3 ) ;
Phosphoric acid (H 3 P0 4 ) ; and
Boric or boracic acid (H 3 B0 3 ).
(2) Vegetable or organic acids, those which contain
carbon as an essential constituent, e.g.
Acetic or the acid of vinegar (C 2 H 4 2 ) ;
Oxalic acid (C 2 H 2 4 ) ;
Lactic acid (C 3 H 6 3 ) ;
Tartaric acids (C 4 H ft 6 ), etc.
22
ACIDS, ALKALIES, AND SALTS 23
Occasionally acids are classed as the hydracids or those
containing no oxygen, e.g. HC1 ; and the oxyacids or those
which contain that element, e.g. HN0 3 , etc.
Hydrochloric acid (HC1) is a strongly fuming gas obtained
by the action of vitriol on common salt. It is also collected
as a by-product in the manufacture of salt-cake.
The gas is very soluble in water, yielding the solution
in which form it is sent into commerce.
It yields the series of salts known as the chlorides, of
which sodium chloride (NaCl) is the best-known member.
Sodium chloride occurs as rock-salt and brine, from which
sources the butter salt and fisheries salt, as supplied to the
baking trade, are prepared. Settled brine is run in a
continuous stream into a long shallow iron pan heated from
below. If the temperature of evaporation is near the
boiling point of the brine, a fine, granular salt separates
out which is raked to the side of the pan, drained, purified,
and sent out as butter salt. Such a product as supplied
by the Cheshire manufacturers often contains 99 per cent,
of pure NaCl.
When the temperature of evaporation is somewhat
below the boiling point, say about 200 F., larger crystals
of a shell-like structure are formed. These are raked to
the side, drained and dried. Such a salt is not quite so
pure as the previously mentioned butter salt, but it has
the advantages of being easily soluble in water and cheaper.
Bay salt is prepared by allowing sea-water, such as the
Mediterranean sea-water, which contains about four per
cent, of NaCl besides other bodies, to evaporate under the
sun's rays in shallow rock tanks that are filled at high tide.
Bay salt, though very suitable for medicinal purposes, is
not fit for breadmaking.
The uses of salt in a bakery. The most important use
is that of conferring flavour on bread and other goods.
The quantities employed vary in different districts for
the same type of bread, and for various types very con-
siderably.
24 CHEMISTRY OF BREADMAKING
For straight doughs the quantities are from 2J to 4 Ibs.
per sack of 280 Ibs. of flour.
For ferment and dough, and sponge and dough processes,
the salt used varies from 3 to 5 Ibs. Where very slow
processes of fermentation are common, the quantity of
salt may go up to 7 Ibs.
For English tin bread the average is 3 Ibs. per sack.
It should be remembered that any quantity above 3J Ibs.
can readily be tasted, whilst at the same time it destroys
the delicate flavour and aroma of high-class bread.
Salt is also a strong antiseptic and germicide ; hence
care must be taken not to use too much or it may check
the fermentative action of the yeast. Again, salt exerts
a considerable influence in toughening and strengthening
the gluten in a dough, while it assists the outside colour
and bloom of bread and smalls.
Where other antiseptics cannot be obtained, strong hot
brine is an excellent remedy against lactic, butyric, and
other bacteria which lurk in the cracks, crevices, and
corners of bakery appliances and of the bakery itself.
Nitric acid (HN0 3 ) is a dense, heavy liquid, colourless
when pure, but often of a yellowish shade owing to the
presence of free oxides of nitrogen. This acid may be
obtained by heating well-dried Chili saltpetre (NaN0 3 )
with strong vitriol. It is a strongly corrosive liquid that
is used in the preparation of high explosives like gun-cotton,
nitro-glycerine, and blasting gelatin. The ancients, who
knew it as aqua fortis, prepared by its aid lunar caustic or
silver nitrate (AgN0 3 ) , a salt used in weak solution for detect-
ing the presence of chlorides in drinking water. Potassium
nitrate, nitre, or saltpetre (KN0 3 ), is a product of the action
of nitrifying bacteria on nitrogenous matter in soils. Nitre
is largely employed in preserving such flesh-foods as tongues
and hams, and also in the manufacture of gunpowder.
Sulphuric acid or vitriol (H 2 S0 4 ) when pure and strong, is
a heavy, oily liquid, even more corrosive than nitric acid.
It is manufactured by several different processes, but all
ACIDS, ALKALIES, AND SALTS 25
depend on the burning of sulphur or a sulphide in air to
form sulphur dioxide, the oxidation of this to sulphur
trioxide, and the absorption of this latter gas by water.
The salts of this acid, which is dibasic, are the acid or
bi-sulphates and the normal salts as sulphate of lime.
Sulphurous acid (H 2 S0 3 ) is a solution of sulphur dioxide
gas in water, which solution smells strongly of burning
sulphur. Its salts, the bisulphites, like the acid, are power-
ful antiseptics, and for this reason are largely used in
bakeries for sterilising the various parts of the plant.
The gas (S0 2 ) is also employed in bleaching hops, grain,
straw, and isinglass, etc. The normal sulphites are
valueless as antiseptics.
Carbonic acid (H 2 CO 3 ), a solution of carbon dioxide in
water, although a weak acid, yields two series of well-known
salts, the normal and bicarbonates. The bi- or acid-carbon-
ate, may be prepared by passing C0 2 into a solution of
caustic alkali, e.g. NaOH+C0 2 =XaHC0 3 , bicarbonate of
soda, a salt employed in conjunction with cream of tartar
for aerating purposes. Both carbonates of the alkali
metals are manufactured in alkali works in enormous
quantities and thus give employment to thousands of
persons.
Phosphoric acid (H 3 P0 4 ) and its salts are prepared either
from mineral phosphates, as apatite, coprolites, etc., or
from animal bones, or from spent char materials.
The acid itself is sent into commerce as sticks of glacial
phosphoric acid, in the powdered form, or in solution. A
weak solution is largely employed by flour millers to steep
a portion of the wheat of their grist, as it is said to improve
the flour. The normal phosphate of lime and its acid salt
are also used by both bakers and millers as bread improvers.
The acid- or super-phosphate is a common constituent of
cream powders, which are cheap substitutes for high-class
aerating materials in confectionery goods.
Boric or boracie acid (H 3 B0 3 ) occurs in nature in weak
solution, but it is mainly prepared from the natural borates
26 CHEMISTRY OF BREADMAKING
such as borax. This acid and the salt borax are powerful
antiseptics, and as such are used in considerable quantities
for the preservation of food-stuffs, especially milk, butter,
bacon, broken eggs, vegetables, and fruits. They are also
constituents of ointments, salves, and other preparations.
The vegetable acids will be considered in a later chapter.
ALKALIES
The name ' alkali ' is given to substances, spoken of as
bases, most of which are obtained from the lower oxides of
a number of metals, and which in solution possess some of
the following properties :
A soapy taste and feel ; they soften and dissolve the
skin ; change neutral or red litmus solution to blue ; and
neutralise acids, forming salts and water, whilst many of
them attack and dissolve metals, such as zinc, aluminium,
and others, evolving hydrogen gas.
Alkalies are either caustic, as caustic soda (NaOH) and
caustic potash (KOH), or mild, the latter name being given
to metallic carbonates which possess alkaline properties.
The more common are : certain compounds of sodium,
potassium, ammonium, lithium, calcium, magnesium, etc.,
which possess the previously mentioned properties.
SALTS
Salts are compounds composed of a base or bases com-
bined with an acid.
Those salts, the base of which is a metal, are known as
metallic salts, e.g. NaCl, KN0 3 , CaS0 4 , etc. These may
be normal, or acid, or basic salts. Such salts may
be prepared in a variety of ways, of which the following
are the more common :
(1) By substitution of a metal for the hydrogen of an
acid, as when zinc is dissolved in sulphuric acid :
Zn -f- H 2 S0 4 = ZnS0 4 -f H 2
Zinc + Vitriol Zinc sulphate + Hydrogen
The salt is zinc sulphate.
(2) By the combination of an acid-forming oxide with a
ACIDS, ALKALIES, AND SALTS 27
base, as S0 3 (sulphur trioxide) with the base CaO (lime),
forming CaSO 4 (calcium sulphate).
(3) By the exchange of hydrogen and metal between
an acid and hydrate or hydroxide, as
HC1 + NaOH = NaCl + H 2
Hydrochloric acid + Caustic soda Sodium chloride + Water
This illustrates the neutralising of an acid with an
alkali, forming a salt and water. When the whole of the
hydrogen of an acid is replaced by a metal, then the salts
are said to be normal ones ; but when only a portion of the
hydrogen is replaced, one or more acid or bi-salts are
obtained, as in the case of phosphoric acid and its salts.
This acid forms a normal and two acid salts, viz., K 3 P0 4 ,
K 2 HP0 4 , KH 2 P0 4 . This latter salt exists as the potassium
phosphate of wheat and flour, and is one of the causes of
flour possessing an acid reaction.
(4) By the combination of a normal salt with an acid-
forming oxide, e.g.
Na 2 S0 4 + S0 3 Na 2 S 2 7
Sodium sulphate + Sulphur trioxide Pyrosulphate of soda
or,
K 2 O0 4 + Cr0 3 K 2 O 2 7
Potassium chromate + Chromium trioxide Potassium dichromate
(5) Basic salts are those formed by the combination
between a normal salt and a basic hydrate or hydroxide.
E.g. if lead nitrate solution be boiled with lead hydrate,
basic lead nitrate is formed :
/N0 3 /OH /N0 3
Pb< +Pb<( = 2P1<
\N0 3 \OH \OH
Lead nitrate + Lead hydrate Basic lead nitrate
Similarly, the formation of the basic lead acetate, which is
so largely used as a clarifying agent in the polarising of
sugar solutions, is a combination of this character.
In addition to metallic salts in which the acid is a
mineral one, there are many salts the base of which is a
metal, but in which the acid is a vegetable or organic one.
28 CHEMISTRY OF BREADMAKING
E.g., the ordinary soaps are sodium and potassium salts
of fatty acids ; cream of tartar is the acid-potassium salt
of tartaric acid.
Further, the hydrogen of an acid may be replaced by an
alcoholic group, as in the case of many of the flavouring
essences, fats, etc., used in the trade. Hence the fats, and
many compound ethers or esters, are true salts. In the
case of the fats, the base is the alcohol glycerin, and the
acid is one of the many fatty acids ; therefore the butyrin,
olein. palmitin, and stearin of butter are salts.
The inorganic constituents of the cereals. These bodies
are intimately associated with the salts, of which they are
almost wholly composed. A chemical analysis of the
mineral matters or ash will show these to be made up of
bases or oxides of metals, especially those of the alkalies
and earthy metals, combined with acid-forming oxides of
the non-metals.
The quantities of the constituents differ considerably for
each of the different cereals, as may be seen by noting the
composition of the mineral constituents of the ash of wheat
and barley given in Chap. VTL, p. 100. There it will be seen
that two salts in each stand out prominently, the phosphates
of potassium and magnesium. The other salts are present
only in much smaller proportions. These two phosphates
form the chief salts in the ash of all cereals, as may be
noticed in text-books on foods. The bases oxides of
potassium, magnesium, calcium, iron, and sodium make
up approximately 45 per cent, of the ash of wheat, while the
acid-forming oxides of phosphorus, sulphur, and silicon,
with minute quantities of chlorine, comprise the remaining
55 per cent. The only other inorganic constituent of
wheat is water. The bases together with the phosphoric
anhydride and water yield the phosphates.
The mineral phosphates are obtained by plants from
the soil, whilst the soil gets its supply by the weathering or
breaking up of the phosphatic rocks in the earth's crust by
natural forces such as rain, frost, the sun's heat, and
ACIDS, ALKALIES, AND SALTS 29
certain constituents of the atmosphere, especially oxygen
and carbon dioxide gases. The element phosphorus, owing
to its intense affinity for oxygen in the presence of moisture,
never exists in the free state ; but in the combined con-
dition it becomes an important factor in all food substances,
in the bones of animals and the embryos both of vegetable
and animal life. The chief compounds of this element are
the oxides and oxy acids and salts derived from these.
Phosphates of calcium and magnesium exist in the bones of
animals, and from this source many of the phosphorus
compounds in common use are prepared. The soluble or
super-phosphate of lime and free phosphoric acid are used
in some of the so-called bread improvers, and also for
sprinkling the semolinas during the milling of flour with
the object of strengthening weak flours. The acid phos-
phate of potash is one of the causes of acidity in plant life
and products derived therefrom.
CHAPTER IV
BAKERY PHYSICS
IN studying the subject of heat, two kinds of measurement
are recognised : quantity of heat, and heat level or intensity
of heat ; hence, two kinds of instruments are required in
taking measurements.
Calorimeters are used in the first case, and thermometers
for registering the intensity of heat and cold.
THERMOMETERS
Many different varieties of thermometers are in common
use, but in the baking trade only three are of importance :
the ordinary mercurial, the pyrometer, and the maximum
and minimum instrument of the Sixe type. A wet and
dry bulb psychrometer is also useful in determining the
humidity or hygrometric conditions of the bakehouse.
The construction of a mercurial thermometer. A piece
of special glass tubing possessing a capillary bore, regular
and. even throughout its length, is first thoroughly cleaned,
then a suitable bulb is blown at one end. The bulb and
tube are filled with pure, clean, dry mercury, and the
contents boiled, after which the tube is sealed off. It is
allowed to rest for a short time and then graduated by
bringing the lower portion of the instrument into melting
ice ; the point at which the mercury column becomes
constant being marked on the stem. Then the whole
thermometer is immersed in steam at the pressure of the
atmosphere and the position of the mercury column again
marked on the stem. The first mark registers the freezing
point, and the upper one the boiling point of water. The
THERMOMETERS, THERMOMETRIC SCALES 31
Fahr.
Cent.
space between is divided evenly according to the scale to
be used. Thus on the Fahrenheit it is divided into 180
divisions, and on the Centigrade into 100, each of which is
a degree. The two thermometric scales in common use
are the Fahrenheit and the Centigrade or Celsius.
Fahrenheit fixed his graduations as zero, the lowest
temperature obtained by mixing together snow or ice and
salt, the freezing point of water at 32, and the boiling
point at 212. Thus between freezing and the boiling
points of water there are 180.
On the Centigrade instrument is the freezing and
100 the boiling point of water.
Hence, F. : C.=1SO : 100, or 9 : 5.
The little diagram of Fig. 1 will serve
to illustrate the relations between the
two scales. These scales may easily
be converted from the one into the other
by observing that 9 F.=5 C., and
making the allowance of 32 in dealing
with the Fahrenheit.
Thus to convert F. to C. :
To convert C. to F. :
(C.xf)+32=:F. .
Three examples will make this quite
clear :
It is required to convert 212 F.
into C..
212-32=180,
lOO C.
,
It is required to find the correspond-
ing F. temperature to 360 C. :
1
~\
212
100
180'<
100^
32 ^
'of'
L Compj
Cherinome
Scales.
irison
trie
^^_^=:648, and 648+32=680 Fah.
5
Prove that 40 C. corresponds with 40 F. :
~ 40 x9 =-72, and -72+32=-40 F.
32 CHEMISTRY OF BREADMAKING
Or the converse :
40 P. 32= 72, and
Fahrenheit thermometers bent at an angle of 90 are
frequently used for registering oven temperatures. Pro-
vided that they are not required to indicate higher readings
than about 650 F. (343-3 C.), they are sufficiently accur-
ate. Above this temperature the readings approach the
boiling point of mercury (678 F., 359 C.). In these and
other cases, especially for cheapness, instruments known as
pyrometers are commonly used. Of these there are many
varieties. For example, Wedgwood, the famous potter,
devised a pyrometer which depended on the contraction of
a piece of baked clay ; Siemens invented an electrical one ;
but for a baker's oven, two different metals or metallic
alloys are soldered together to form a solid bar or ribbon.
The differences in the expansion and contraction of the
dissimilar metals is utilised to move an indicator arranged
on a dial. Expansions move the indicator up towards the
highest divisions, while contractions cause it to work in
the opposite direction on the clock-face-like dial. Bakers'
pyrometers generally range from 200 to 700 F.
Maximum and minimum thermometers are of use in the
bakehouse to register the highest and lowest temperatures
respectively. The wet and dry bulb thermometer, or
Mason's hygrometer or psychrometsr, is also a useful
instrument in the bakery, since, as already mentioned, it
gives the baker information regarding the amount of
moisture present in the atmosphere of the bakery, and
may thereby tend to prevent the ' skinning ' of surfaces of
dough exposed.
BAROMETERS
Barometers are instruments employed for measuring the
pressure of the atmosphere. They are of two types : the
mercurial and the aneroid. The simplest form of barometer
consists of a glass tube of regular and even bore throughout
its length of about thirty-three inches. One end is sealed
and the other left open. The tube is carefully filled with
BAROMETERS
33
Torricelli
Vacuum
Mercury
Column
pure dry mercury, all the air bubbles removed by heating,
and the tube then inverted in a cup or other reservoir
containing mercury (Fig. 2). It
should be so fixed as to allow
the mercury to pass up and down
the tube easily.
If the barometer is placed at
the normal sea-level with a tem-
perature of 60 F., the mercury
column, when measured from the
level in the reservoir, should stand
at a height of 29-922 inches, or
approximately 30 inches. If the
bore is of one square inch section,
the quantity of mercury in the
column supported by the pres-
sure of the air on the mercury in
the reservoir is found to weigh
14-73 Ibs., thus giving rise to
the popular statement, ' The
weight of an atmosphere is 15
Ibs.' A water barometer would
require a tube of about 35 feet
in height, as the normal height of a water barometer
is about 34 feet. A barometer, as its name indicates, is
used for measuring the pressure of the atmosphere.
Pascal, a celebrated French savant, demonstrated the
value of a barometer for this purpose by carrying his
mercurial instrument up the highest peak of the Puy-
du-D6me in France, and noting the gradual fall of the
mercury until he reached the top, at which point the
level became constant. His figures showed that for every
ninety feet in height ascended the column dropped one-
tenth of an inch.
THE METRIC SYSTEM OF WEIGHTS AND MEASURES
In all scientific work the metric system of weights and
measures is commonly used, therefore it is essential that
C
Reservoir
Mercury
Fig. 2. A Mercurial
Barometer.
34 CHEMISTRY OF BREADMAKING
students should possess a knowledge of the system. This
decimal system owes its origin to the French philosopher,
Gay-Lussac, who flourished about the end of the eighteenth
century.
There are three chief units in the system, viz. :
The metre, or unit of length, which equals 39-371
inches.
The gram, or unit of mass (weight), which equals 15-432
grains.
The litre, or unit of capacity, which equals 1-761 pints.
The subdivisions of the units are :
deci which equals 0-1, or ^- of the unit.
centi 0-01, or
milli 0-001, or
The multiples are :
deka which equals 10 times the unit.
hekto 100
kilo 1000
Thus in linear measure
1 millimetre = 0-039371 or nearly ^ of an inch.
1 centimetre = 0-39371 inch.
1 decimetre = 3-9371 inches.
1 metre = 39-371 inches.
1 dekametre = 393-71 inches.
1 hektometre= 3937-1 inches.
1 kilometre = 39,371 inches, or 1093-6 yards, or
0-621 miles.
In the measure of mass or weight
1 milligram = 0-015432 English grains.
1 gram = 15-432 English grains.
1 kilogram = 15,432 English grains.
7000 grains =1 Ib. avoir., therefore a kilogram is equiva-
lent to 2i Ibs., and a demi-kilogram to 1 ^ Ibs., or approxi-
mately 1 Ib.
A gram of pure water at 39-2 F. (4 C.) occupies a
volume of one cubic centimetre (1 c.c.).
A kilogram of water occupies a volume of one litre, or
1'761 English pints (roughly If pints).
HEAT CALCULATIONS 35
In measures of capacity
1 millilitre or c.c. 0-061027 cb. inches.
1 litre or cb. decimetre = 61 '027 cb. inches, or 1'761 pints.
1 hektolilre or 100 litres = 6,1027 cb. inches, or 176 pints, or 22 gals.
1 kilolitre or 1000 litres =61,027 cb. inches, or 1,761 pints, or 220 gals.
A gallon of water weighs 10 Ibs. or 160 oz. or 70,000
grains. One pint weighs 20 ozs., hence a fluid oz.= 7T 1 7T pint.
One oz. equals 28-35 grams, occupying a volume of 28-35 c.c.
One cubic inch equals 16-38 c.c., and a gallon equals 277-274
cubic inches. A litre is the cubical measure of 0-1 or -^
metre in the side ; hence a cubic vessel constructed on a
square, the length of a side of which equals one decimetre,
or 3-9371 inches, will contain exactly a litre of a liquid.
In flour and bread analyses, measuring vessels, such as
pipettes, flasks, and burettes, are invariably graduated in
cubic centimetres.
HEAT CALCULATIONS AND MECHANICS
A calory or heat unit is the quantity of heat required
to raise unit weight of water through unit of temperature.
In the British Isles this heat unit is the quantity of heat
required to raise one pound of water through one degree
Fahrenheit. In scientific circles, it is the quantity of heat
required to raise one gram of water through one degree
Centigrade or the gram-calory. Frequently, a unit one
thousand times greater is taken as the standard for heat
measurement.
In the bakehouse it is a regular occurrence to raise the
temperature of a quantity of water. Instead of running
heated water into cold water, by chance, the calculated
quantity of hot water or steam is mixed with the cooler
water, thus giving the mixture of water at the proper or
required temperature. Several examples of useful heat
calculations are here given to assist the beginner.
(1) How many heat or thermal units are there in five
gallons of water at 85 F. ?
A gallon of water weighs 10 Ibs.
Therefore 5 galls, weigh 10x5=50 Ibs.
36 CHEMISTRY OF BREADMAKING
As each degree that 1 Ib. rises corresponds to a thermal
unit, then 50x85=4250 units of heat. More accurately
an allowance should be made for the fact that water
freezes or congeals at 32 F. But generally each degree
is taken as a heat unit as shown in the example.
(2) Calculate the mean temperature of two different
quantities of water when at different temperatures after
thoroughly mixing together.
E.g. 28 galls, of water at 45 F. when mixed with
14 galls, at 180 F.
28 X 10=280 Ibs. and 280x45 =12,600 thermal units.
14 x 10=140 Ibs. and 140 X 180=25,200
Total 420 Ibs. containing 37,800
37,800
420
90 F. temperature of the mixture.
(3) It is required to raise the temperature of 8 galls, of
water from 55 F. to 102 F. How much water at 212 F.
is necessary ?
The difference between 102 and 55 is 47.
8 galls, weigh 8 X 10=80 Ibs.
The number of thermal units required will be
80X47=3760.
Each pound of water in cooling from 212 to 102 gives
up 110 thermal units;
therefore ^=34-13 Ibs., or 3-418 galls, of water
are required.
(4) Given 55 galls, of water at 62 F., how much boiling
water at 212 and how much steam at 322 F. will be
required separately to raise the temperature to 115
F. ?
55x10=550 Ibs. of water at 62 F.
115 -62=53 of difference in temperature.
550x53=29,150 thermal units required.
HEAT CALCULATIONS 37
Each pound of boiling water gives up 97 in cooling to
OQ 1 KA
115; therefore ' =300-52 Ibs., or 30-052 galls, of hot
water are required.
Each pound of steam at 322 F. gives up in cooling to
115 the following :
1 lb. of steam at 322 gives up 110 thermal units in cooling to 212,
1 lb. of steam gives up 967 thermal units in changingto water,
1 lb. of boiling water gives up 97 thermal units in cooling to 115,
. '. each lb. of steam gives up 1,174 thermal units in cooling to 115,
hence ^-^L 24-83 Ibs. of steam required.
J. j 1 /TC
Note. In Chap. II., p. 15, the reader will see that
the latent heat of steam was given as 967 British thermal
units.
(5) How much cold water at 48 F. is required to cool
down 5 galls. 2 qts. of water at 200 to 87 F. ?
5 galls. 2 qts. weigh 50+5=55 Ibs.
In cooling from 200 to 87 each lb. loses 113.
Therefore 55x113=6215 thermal units to remove.
Each lb. of water at 48 absorbs 87 48=39 thermal
units, hence -1- = 159-359 Ibs. or 15-936 galls, of the cold
39
water are required.
Specific heat (sp. ht.) has been defined to be the ratio of
the quantity of heat required to raise unit weight of a
substance through unit of temperature, compared with
the quantity of heat required to raise unit weight of water
through unit of temperature. The specific heat of water
is taken as unity or 1, and that of all other bodies as
decimals of this. Thus the sp. ht. of flour, malt, and cereals
varies between 0-39 and 0-5. In the following problem show-
ing the application of sp. ht., that of malt is taken as 0-42.
(6) A mash is to be made at 145 F. with 22 Ibs. of malt
and 80 Ibs. of water. The temperature of the malt is 56.
Find the temperature of the water. Let #=the required
temperature.
38 CHEMISTRY OF BREADMAKING
The number of thermal units in the malt will be
22x56x042=51744 or say 517-5.
80x#Xl=80# or number of heat units in the water
before the mixing together or mashing ;
and 80.+042 X 22 X 56- 80 X 145+042 X 22 X 145.
Therefore g 8Q X ] 45 +042 X 22 X 145 ~ 042 x 22x56
80
11600+1339-85174
80
12422-4
-155-28 F.
80
Therefore the 22 Ibs. of malt at 56 will require to be
mixed with 80 Ibs. of water at 155-28 F. in order to pro-
duce a mash at 145, the best temperature for diastase.
Mechanics in a bakery. In all machine bakeries a
knowledge of mechanics is necessary. This branch of
study can here only be considered in a very superficial
manner, hence a good text-book on the subject should be
consulted.
In connection with the transmission of motion by means
of pulleys, it is essential to consider the mensuration of the
circle very briefly, and more especially its circumference.
If D is the diameter, or twice the radius, of a circle, then
22
?rD is the circumference, where K= or 3-1416. If r is
the radius in feet, then 2?r times this radius equals the
circumference in feet.
Example. Find the circumference of a circle whose
diameter is 3J feet ?
22 22 7
The circumference =7rD= X 3 J= - x 5.
9 9
=|=11 feet.
Next, assume a disc to be rotating about a fixed axis,
with a speed of 80 revolutions per minute.
Again, consider a point A (Fig. 3) at a distance r from
the centre. Then from the above it is clear that the
MECHANICS 39
distance through which A moves in one revolution is
i.e. the distance moved through in 80 revolutions per
minute will therefore equal 80 X 2?rr or 80 X ^D.
Thus take the case of a pulley of
diameter D over which a strap is pass-
ing, the revolutions of the pulley being
equal to N. Also assume that the belt
is moving at the same speed as the rim
of the pulley ; it is evident from the
above that the velocity of the belt in
feet per minute will be
where D= diameter in feet, and N= revolutions per
minute.
Example. A pulley of 3 feet diameter is keyed on to a
shaft which is running at 250 revolutions per minute. Power
is transmitted from this pulley to a machine by a belt. Find
the speed of the belt in feet per minute and also in feet per
second.
The speed of strap in feet per minute
NX22XD
7
250X22X3^16500
7 7
235-7
=235-7 feet per minute.
=3-928 feet per second.
60
If the above formula be examined it will be observed
that if the diameter is doubled, then the speed is also
doubled ; similarly if it is increased in any proportion,
then the speed is increased in a similar proportion ; that
is, the rim speed is accelerated directly as the diameter,
for a constant number of revolutions per minute.
The ratio of the revolutions of two pulleys connected
40
CHEMISTRY OF BREADMAKING
by a belt may be considered. In this it is assumed that
there is no slipping of the belt.
Fig. 4. Driving by Belt.
The surface velocity of either pulley will be the same,
because in each case it is equal to the velocity of the strap.
The surface velocity of the driver A (Fig. 4)
22
The surface velocity of the follower
99
=nX~Xd.
But these are equal
or
N d , N.D
_= or d= -
D
n
n=
n
N.D
In exact work it is necessary to make corrections for
the thickness of the belt.
From the formulae obtained it is possible to deduce the
following self-evident rule for ascertaining an unknown
term, thus :
Multiply those two numbers which belong to the same
pulley and divide the product by the third number ; then
the quotient is the term required.
The belt is not used where an exact velocity ratio is
required.
MECHANICS 41
Given the HP. (horse-power) to be transmitted, the
diameter of the pulley, and the number of revolutions per
minute of the pulley. Find the width of the belt.
HP.= = X XD.N, where V is the velocity of
600 600 7
the belt.
.,,, . . , HP. X 4200 1
w = width m inches = x -FT\f
I.L JD.jN
HP. x 192
-D3T
where D=diameter in feet, N^revolutions per minute.
Example. Assume that a dough mixer requires 4 HP.
to drive it. Also that the pulley is 18 inches in diameter
and that it makes 150 revolutions per minute. Then
width of belt, w= =3% inches.
l*o x lou
For very slow speeds, the values of w work out very high,
in which case a double-ply belting would be used of half the
width obtained by the above calculation. For example, if
the speed were 75 revolutions instead of 150, then the width
of the belt would be 7 inches, or a double ply of 3J inches.
Again if the width of belt, the HP, and the diameter
of the pulley are fixed, then the number of revolutions per
minute at which it would be safe to run can readily be
found.
CHAPTER V
HEAT AND PHYSICAL PROBLEMS
HEAT 3 is the name given to a very well-known sensation
which the agent produces when in contact with the human
body. Cold is the term applied to the opposite sensation,
but experience shows that both terms are only relative,
for what to one person would be termed hot, to another
might produce the sensation of being cold. Two bodies
may be said to be equally heated when in contact there is
no interchange of heat between them.
A heated body gives off its heat in two ways : (1) By
being in contact with a cooler body ; (2) By radiation
through space.
Heat radiates through space in straight lines in all
directions and at the rate of 186,000 miles per second.
Heat, like light, consists of vibrations of enormous
velocity, and with increase in temperature there is a great
increase in the rate of the vibrations and a corresponding
decrease in the wave-length of the vibrations. A just
perceptible red heat is about 400 C. (752 F.) ; a cherry-
red heat is 900 C. (1652 F.) ; whilst a white heat is
1800 C. (3272 F.).
The sun is the great source of heat on the earth, and if a
beam of the sun's light be passed through a glass prism the
spectrum so obtained consists of a band of colours spoken
of as the colours of the rainbow. These are red, orange,
yellow, green, blue, indigo, and violet. Beyond the red at
the one end and the violet at the other, there are bands of
waves, not visible to the human eye, known as the ultra-
red and ultra-violet respectively. If these are studied it
will be found that the ultra-red rays produce the sensation
42
HEAT 43
of heat, and the ultra-violet intense chemical action. It
has further been shown that the sensation produced by the
ultra-red rays of the sunlight agrees with that obtained
by heating a rod of metal such as a poker to such a tem-
perature that when brought into a dark room the red heat
is faintly perceptible.
Heat may be propagated in three ways :
(1) through solids by conduction ;
(2) through liquids and gases by convection currents ;
(3) through space by radiation.
All these processes are involved in the baking industry ;
it is therefore desirable that the workers should possess
some knowledge of them.
Conduction of heat. Conduction is the name given to
the process by which heat is propagated through solid
matter. In this process there is no
motion of progression of the particles
of the solid themselves, but as
particles of the solid which are in
contact with those around them
become heated or cooled, the sensa-
tion is conveyed by the contact to Kg. 5. Conduction
the other particles, consequently the of Heat,
whole of the solid will gradually become heated or cooled.
In the case of metals the process goes on fairly rapidly,
whilst with non-metals, mixed materials as slate, wood, and
many other solids, the heating or cooling is very slow.
Metals are therefore termed good conductors, and the other
bodies poor or even non-conductors. The heating or
cooling proceeds until the whole of the solid is at the
same temperature.
The process may be illustrated by the sketch of Fig. 5.
Conceive of a bar of metal made up of an almost infinite
number of particles represented by the circles. Heat is
applied to the bar at the point A. The particle being in
contact with particles on all its sides communicates the
heat to them ; they in turn communicate the heat
CHEMISTRY OF BREADMAKING
to other particles until the whole bar becomes equally
heated.
Conduction is evidently carried out in two stages.
The first is the variable one, during which the heat is
applied and the parts of the solid are increasing in tem-
perature. The second stage is that in which all parts
have become equally heated and every particle will give
out as much as it receives, thus verifying Stewart's well-
known Theory of Exchanges, and this stage itself is clearly
the permanent one.
The following short table gives a comparison of the con-
ducting power of metals, based on silver as possessing the
highest conductivity.
Metal.
Conductivity.
Metal.
Conductivity.
Silver (Ag),
Copper (Cu), .
Gold (Au), .
Brass,
100-00
77-63
53-20
33-10
Zinc (Zn), .
Tin (Sn),
Iron (Fe), .
Bismuth (Bi),
19-89
14-52
11-94
1-92
The good conductivity of the metals and the poor
conducting power of wood, slate, chalk, etc., explains the
sensation of cold that a person experiences when touching
a metal surface and the opposite sensation when in contact
with wood, both materials being in the same room and at
the same temperature. It also partly explains why a
copper or brass cooking vessel is more efficient than an
iron one for its purpose.
Convection. Convection is the name given to the process
by which heat is propagated through liquids and gases.
In this process there is an actual movement of progression.
For example, a liquid contained in a vessel is heated from
below ; the particles near to the source of heat expand
and so become lighter or of less density than the particles
above ; they therefore rise and the cooler heavier particles
HEAT 45
flow downwards to take their place, in this way setting up
convection currents. The same applies equally to gases ;
so in general, when different parts of a liquid or gas are
heated to different temperatures, like differences of density
are caused, leading to the formation of currents which are
known as ' convection currents.'
Numbers of examples of this occur in the daily life of a
baker, e.g. the pans and kettles that are heated over gas
or other sources of heat ; the filling of the attemperating
tank in connection with the dough mixer, based on the
principle that hot water is lighter than cold, therefore the
hot water is run into the tank first, and the heavier cold
water next which sets up convection and thus tends to
equalise the temperature. The heating of buildings by
hot water is similar ; the water in the boiler becomes heated
and lighter, consequently it rises to the highest point,
whilst the cooler water flows by the return pipe to the boiler
setting up a complete circulation. Even a steam-pipe oven
is dependent partly on convection, partly on conduction,
and very largely on radiation. Convection also plays a
highly important part in meteorology. Moreover, the
natural ventilation of our buildings is largely dependent
on both convection currents and the diffusion of gases.
Radiation. Radiation is a process for the dispersion
and dissipation of heat. From its source radiant heat
travels in straight lines and at the same velocity as light,
viz., 186,000 miles per second. As the heat is propagated
in straight lines, it does not warm the intervening space.
Radiant heat is, in fact, not heat at all, but a form of energy
that can be easily changed into heat. The fact that it
travels at the same rate as light and conforms to the same
laws as light rather points to such a conclusion.
Of the three processes by which heat is propagated,
radiation is almost instantaneous ; convection is slow ;
conduction very slow by comparison. It is important to
remember that heated bodies radiate heat in straight lines
in all directions ; thus it is that the space of the baking
46 CHEMISTRY OF BREADMAKING
chamber becomes heated and is able to transmit its heat
to the dough, which in this way is baked.
THE MICROSCOPE AND POLARIMETER
Light, like heat, consists of vibrations in which the
wave-length is very minute and the velocity enormous.
Light vibrations require the presence of an extremely
subtle fluid, of which our senses can take no cognizance,
known as the ethereal medium. These vibrations are
transverse to the direction in which the beam is being
transmitted, while those of sound are longitudinal. The
phenomenon of light is the cause of vision and enables
us to see objects ; it is also the all-important factor in the
use of such optical instruments as are in part constructed
of lenses, like the microscope and polariscope or polarimeter.
Lenses. Before proceeding to discuss the microscope
it is first necessary to understand the action of lenses.
A lens is a piece of glass bounded by
two surfaces which are portions
of spheres. Of these there are two
classes, the converging and diverging
lenses. The converging are also
known as convex lenses, while the
diverging are concave. The former
alone are used in microscopy, as they
are the only magnifying ones.
Fig. 6. A There are three different forms PlancT
Double- O f convex lenses : the double con- convex
ins> vex, the plano-convex, and the con- Lens.
cavo-convex. The double convex (Fig. 6) when placed in
a frame forms the simple microscope or burning-glass.
The plano-convex (Fig. 7) is generally used in com-
bination with other lenses both in the microscope and
optical lantern.
When beams of light enter a lens they are bent out of
their course or refracted on entering and again on leaving
the lens. These beams all converge to a point, which lies
THE MICROSCOPE 47
on a straight line passing through the centre of the lens. 4
This straight line is the principal axis, and the point on
either side of the lens and at equal distances from it is the
principal focus of the lens ; while the distance between the
lens and this point is its focal length.
The formation of images. Images formed by lenses are
either real or virtual. When an object is placed at a dis-
tance of less than twice the focal length of the lens, a real
and magnified image is formed on the other side of the
lens. If placed at exactly twice the focal length, a real
image but not magnified is obtained, and if placed at a
distance greater than twice the focal length, a real but
diminished image is formed. When the object is placed
between the principal fo< us and the lens, a magnified virtual
image on the same side of the lens is formed. This latter
is the construction in the case of a single microscope or
simple magnifying glass. A convex lens of shorter focal
length than the eye is placed at a distance rather less than
the focal length of the lens from the object, whereby a
virtual and magnified image is the result.
The compound microscope. A simple form of compound
microscope is composed of a stand carrying two lenses, the
lower of the two being the objective and the upper one
the ocular or eye-piece. The objective forms a real and
magnified image on the other, that is the upper, side of
the lens ; this image is arranged to fall between the
principal focus of and the upper lens, thus giving a virtual
and magnified image, which may be observed by looking
down through the eye-piece or ocular. Such an instrument
was first devised by Hans and Zacharias Janssen, two
Dutchmen father and son about the year 1590.
A modern compound microscope (Fig. 8) has the following
parts : A firm stand with telescopic tube, a hinge, two
motions the rack and pinion or coarse adjustment, and
the micrometer or fine adjustment a stage with sub-stage
fittings, viz., the Abbe condenser and reflector, an iris
diaphragm, centering arrangement, and a plano-concave
48
CHEMISTRY OF BREADMAKING
mirror. At the upper end of the telescopic tube is the
fitting T! to receive the ocular, at the lower end a double
Fig. 8. Longitudinal Section through Compound Microscope.
{By permission of Messrs. E. Leitz, London.]
THE MICROSCOPE
49
or triple nose-piece on which the objectives may be screwed
as at T. An image of the object PQ is formed at Q-f v and
this is again multiplied by the ocular at T l to give the magni-
fied image at Q X P X . The stage is frequently fitted with a
mechanical arrangement to enable the observer to make
accurate measurements. The loose fittings consist of a
series of five Huyghenian oculars, various objectives both
dry and oil-immersion, polariser and analyser for starch
and other special work, together with micrometer scale
attached to ocular No. three, and sundry micro-slips three
inches long by one inch wide of white or colourless glass,
cover glasses, etc. For very useful and instructive in-
formation concerning lenses generally and their employment
in the construction of microscopes the new edition of the
work by Drs. Carpenter and Dallenger on the microscope
will be invaluable in aiding a worker to get the best out
of a good instrument.
The Huyghenian oculars of themselves give the following
magnifications :
Number.
l
2
3
4
5
Focus in }
Millimetres /
50
40
30
25
20
Magnification \
in Diameters/
3
4
5-5
7
9
The magnification due to an objective may approximately
be taken as follows :
The one-inch gives 10 diameters,
The half -inch gives 20
The one-eighth of an inch gives 80 diameters,
The tenth of an inch gives 100 diameters, etc., when the
draw tube is at its full length of ten inches, which is that of
normal vision ; hence the total magnification in diameters
may be found by multiplying the magnification due to the
D
50 CHEMISTRY OF BREADMAKING
objective by that due to the ocular. Example. A No.
4 ocular and an eighth of an inch objective.
\ inch gives 80 diameters.
80X7=560 diameters.
Or, more accurately,
Magnification due to ocular x Magnification due to objective x Length of tube
10
7 x 80 x 10 inches .
= ^r = 560 diameters.
A good microscope ought to be capable of giving
Power of penetration,
Brightness of field,
Flatness of field,
Sharp and clear definition,
Great resolving power,
Freedom from chromatic and spherical aberration.
As a good microscope is very delicate in its parts and
easily injured, great care should be observed in its treat-
ment. When not in actual use, it ought to be placed in its
case or put under a glass shade to protect it from dust.
The oculars and objectives should be cleaned with a piece
of soft tissue paper or a fine chamois leather, both free
from gritty particles which would scratch and spoil the
lenses. Under no circumstances whatever should it be
allowed to stand in the direct light from the sun.
Polarimeters (polariscopes). A polarimeter is an instru-
ment for measuring the amount of bending out of its course
or refraction which a beam of plane polarised light suffers
on passing through a column of liquid which possesses
optical activity.
Polarised light, which to the naked eye resembles ordinary
white light, consists of vibrations in one plane only. Light
may be polarised by either reflection or refraction single or
double. For the purposes of ordinary polarising instru-
ments used in the analysis of sugar solutions or other liquids
possessing optical properties, the process by double re-
fraction alone is employed. All doubly refracting crystals
52 CHEMISTRY OF BREADMAKING
such 1 &s tourmalin^ ^&d Iceland spar possess this power.
When a beam of ordinary light passes through one of these
crystals, except in its optical axis, the beam is resolved into
the ordinary and extraordinary rays. This latter ray if
passed through a second crystal behaves in a peculiar way
and is said to be ' polarised.' The plane in which a ray of
polarised light is reflected is known as the plane of polarisa-
tion. If the beam of polarised light vibrates in parallel
straight lines, the beam is said to be plane polarised.
The most useful crystals for the purpose of producing
polarised light are rhombs of calc or Iceland spar (CaCO 3 ).
The Nicol prism is such a crystal split along its optical axis,
that is, through its shorter diagonal, and then fixed together
again with Canada balsam. Two such prisms are employed
in the construction of polarimeters, one to act as the
polariser and the other as the analyser, the space between
them being occupied by the tube containing the optically
active liquid. The theory of a polarimeter is fairly easy
to understand : the beam of sodium (yellow) light or white
light passes through the first Nicol or polariser ; emerging
in a polarised condition it passes on through the liquid
contained in the tube where its plane is bent to the right
or left hand according as the opticity of the liquid is dextro-
or Isevo-rotatory ; it then enters the second Nicol or
analyser, which must be rotated to the left or right until
its principal section, which was parallel to that of the other
prism, is in a position to allow the refracted beam to pass ;
the amount of bending can then be read off on the scale of
the instrument.
From the above, it follows that some substances turn the
plane to the right hand or are dextro-rotatory, e.g. sucrose,
maltose, dextrose, and dextrins ; others turn it to the left
or are Isevo-rotatory, as Isevulose, invert sugar and many
of the proteids. The dextro bodies are signified by the +
and the laevo bodies by the sign.
The construction of a Laurent polarimeter. This instru-
ment consists of a tube, in the centre of which is fixed the
THE POLARIMETER
53
polariser (Figs. 9 and 10). At the end of this tube near the
sodium flame, in the better-class instruments, is fixed a
Circular Telescopic
Scale ^*| Eye-piece
1 1
\
Prism of Diaphragm Containing Tube for Liquids Analyses
Bichromate and Quartz
Fig. 10. The arrangement of parts of a Laurent Polarimeter.
crystal of bichromate of potash to absorb all the beams
of light with the exception of orange or yellowish coloured ;
hence* yellowish light only passes through the polariser,
and from the polariser the extraordinary ray comes out
at the end of the tube. Here is placed a disc or plate of
quartz exactly 3-75 millimetres in thickness, and agreeing
with an angular rotation of 22. This gives the half-
tint, and these instruments are called half-tint instruments,
because half of the quartz is dark, and the other half light.
There is an open portion of the polarimeter so arranged that
a tube of two decimetres in length containing a solution
may be enclosed.
The remaining portion of the instrument is another tube.
In the centre of this tube is placed the second Nicol or
analyser, and exactly in the centre of this Nicol is arranged
the stand on which the graduations and vernier are fixed.
This Nicol is made to revolve in two directions, and the
amount is shown by the circular plate.
There is further a telescopic arrangement for examining
and magnifying the beam of light.
There are two general classes of polarimeters :
(1) The half-shadow instruments which require a
monochromatic light, and
(2) Instruments which use white light.
54 CHEMISTRY OF BREADMAKING
The only difference of construction between these two
is that compensation must be made where light is used of
all degrees of refrangibility. Thus red rays give a rotation
of 19, orange gives 21, and sodium light about 22 ;
at the far end of the spectrum, indigo gives 38 and violet
41, so that between these numbers 19 and 41 come
beams of all degrees of refrangibility, and hence compensa-
tion must be made. This is done by introducing lenses
and crystals which have the effect of darkening the instru-
ment. The most important of the half- shadow instruments
are the Laurent and the instruments the modification of
which led up to the Laurent.
In Fig. 9 AA are the spoons or cups of platinum gauze
to hold the salt for giving a yellow monochromatic jet in
the Bunsen burners, which have collars at V for opening
or closing the air-holes. B is the lens screwed on to the
tube I, which itself screws on to the barrel E. The latter
carries a diaphragm with a small hole which receives a cap
containing a crystal of potassium bichromate used when the
liquids are colourless. The lever K, -fixed on the polarising
tube R, can be rotated by the crank J, and this is moved
by the shaft X and lever U. The diaphragm D, one half
of which is covered by a plate of quartz, is in line with the
telescope O,H. The mirror M throws the light from the
burners on to the divisions of the disc C, and N is the lens
for reading the divisions of the scale.
Amongst white light polarimeters mention may be made
of the Soleil-Duboscq-Ventski and the instruments coming
previous to them. One of the best of these is that made
by and known as the Schmidt-Haensch.
CHAPTER VT
THE ORGANIC CONSTITUENTS OF THE CEREALS
THE study of organic chemistry is of the utmost importance
in connection with food-stuffs. It is therefore advisable to
give a short introduction to this subject.
By organic chemistry is understood the chemistry oi
the carbon compounds, or better the chemistry of the
hydrocarbons and their derivatives. As there are many
thousands of these compounds, it is easy to perceive that
the study of this subject must be thoroughly systematised
or nothing but confusion would result. It includes all
bodies of which carbon is an essential constituent ; hence
all the component parts of animal and vegetable life, with
the exception of the mineral salts, are carbon compounds.
To these must be added the many compounds which are
built up by synthesis in the chemical laboratories, and the
numerous substances obtained in the destructive distillation
of coal, peat, wood, shale, the many tars, bones and
petroleum oils.
All of them may be classified, according to the elements
of which they are composed, and the relation they bear to
one another. Those composed of carbon and hydrogen
alone are the hydrocarbons, a numerous class of important
and useful compounds, including the rock oils or paraffins,
the terpenes and the aromatic or benzene derivatives.
The compounds composed of carbon, hydrogen, and
oxygen form a still more numerous class. These include
the alcohols, and also the carbohydrates, which latter are
neutral compounds, neither salts nor oxides, composed of
carbon and the elements of water. Closely related to the
carbohydrates are the alcohol derivatives, the aldehydes,
55
56 CHEMISTRY OF BREADMAKING
ketones, and acids. The fats also belong to this group,
since, although not carbohydrates, they consist of the same
three elements. In chemical composition, the fats are
glycerides or compounds of glycerin with the fatty acids,
and hence they are salts.
The next important class are those containing the
elements carbon, hydrogen, nitrogen, oxygen, and sulphur.
This class includes the albumenoids and proteins. Associ-
ated with them are the nucteins, still more complex bodies
composed of the five elements of the proteins together with
iron and phosphorus.
Other groups of organic bodies contain the halogen
elements chlorine, bromine, and iodine ; or contain some
metal such as do the metallo-organic compounds.
If some of the important members of each class be
studied, then a fairly accurate idea of the whole is acquired.
A few important and useful groups of compounds are
considered in this chapter under the following heads :
alcohols, acids, fats, carbohydrates, and nitrogenous con-
stituents of the cereals.
The organic constituents of the cereals may be divided
into the nitrogenous and the non-nitrogenous bodies.
The nitrogenous include the proteins, nucleins, derivatives
of these two groups or hydrolytic products, and the soluble
ferments or enzymes.
The non-nitrogenous comprise the carbohydrates, organic
or vegetable acids, and the fats or glycerides. Under the
heading carbohydrates are included the sugars, cellulose or
fibrous compounds, the starches, dextrins, gums, and other
related bodies. Reference to Chap. VII., pp. 99-101, will
give a fairly comprehensive idea of the quantities of these
organic bodies present in the more common cereals.
THE ALCOHOLS
The word ' alcohol ' is a generic term applied to a large
number of organic compounds which are weak bases, and
yield salts spoken of as ' esters ' or ethereal salts. They
may be classified According to their behaviour towards
ORGANIC CONSTITUENTS OF THE CEREALS 57
reagents, or to their formulae. Thus they are primary,
secondary, or tertiary according to their behaviour towards
oxidising reagents ; or they are monohydric, dihydric,
trihydric, or polyhydric alcohols, according to the number
of hydroxyl or OH groups contained in their composition.
The most important monohydric alcohols to a baker and
confectioner are wood-spirit or methyl alcohol (CH 3 .OH),
and spirits of wine or ethyl alcohol (C 2 H 5 .OH). Both of
these are primary alcohols because when gently and
partially oxidised they yield an aldehyde, and when
completely oxidised an acid ; thus, methyl alcohol yields
first formaldehyde and then formic acid. Formaldehyde
is sold commercially as formalin, a powerful antiseptic and
germicide. It exists in nature in the bright green tips of
growing grass and other vegetation. Ethyl alcohol when
similarly treated yields acetaldehyde and then acetic acid,
the acid of vinegar.
Glycerin is an example of a trihydric alcohol. It is at
the same time both a primary and secondary alcohol.
This body will be further mentioned in connection with the
fats. The polyhydric alcohols are closely related to the
sugars, and like glycerin may be both primary and
secondary alcohols at the same time.
Wood-spirit or methyl alcohol (CH 3 .OH). Methyl alcohol
is one of the products formed in the destructive distillation
of wood in iron retorts. Gaseous bodies are given off and
charcoal is left behind in the retort. Some of the gaseous
compounds condense to a liquid, which contains crude
acetic or pyroligneous acid, acetone, wood-spirit, etc., and
wood-tar. The non-condensable gases are used up in heat-
ing the retorts or for lighting purposes. After settling so
as to eliminate the tar, the acid liquors are distilled and the
vapours passed through milk of lime. The acetic acid is
neutralised, forming acetate of lime, whilst the neutral gases
like acetone and wood-spirit which pass over are collected
separately and subjected to fractional distillation in order
to obtain the wood-spirit.
58 CHEMISTRY OF BREADMAKING
This is a liquid of low boiling point, 150 F. (66 C.)
and sp. gr. 0-7963, which is largely employed as a solvent
for lacs, varnishes, resins, etc., and for methylating silent
spirit or spirit of wine, thus giving the ordinary methylated
spirit. A further portion is used for the manufacture of
formalin, a powerful antiseptic containing about forty
per cent, of the active agent, formaldehyde.
Spirits of wine or ethyl alcohol (C 2 H 5 .OH). Spirits of
wine is a liquid which has been known to exist, and to give
the special and peculiar properties to alcoholic beverages,
from the earliest times. Even savage and barbaric peoples
have known how to prepare both alcoholic liquors and
ardent spirits. The body is always manufactured by the
fermentation of sugar solutions and thus gives rise to some
of the greatest industries on the earth's surface, these
including brewing and distilling and the production of
wines, cordials, and liqueurs.
The preparation of alcohol is conducted as follows :
Raw grain, as oats, rye, wheat, or maize, is cleaned and
crushed between heavy rolls, then mixed with about one-
third its weight of crushed barley malt. The mixture is
now made into a kind of thin porridge with water at 150
to 152 F. so as to obtain a mash of 142 to 145 F.
After standing for three hours the liquid is run off and any
sugars left in the grains are washed out with hot water.
The ' wort ' or sweet liquor, consisting chiefly of a solution
of maltose, is cooled rapidly to 68 or 72 F. and filtered
to take out floating particles. It runs from the filter press
into large fermenting vats where it is mixed with fresh,
strong yeast. Fermentation proceeds rapidly for some
hours, and when the sp. gr. of the wash or fermented liquor
has gone down to nearly 1-000 the wash is freed from yeast
and passed into a patent wash-still in which the alcohol is
separated from the other products of fermentation by one
distillation.
Such spirit is rarely of less than 84 per cent, strength,
and is known as rectified spirit or silent spirit. By another
ORGANIC CONSTITUENTS OF THE CEREALS 59
distillation it may be brought up to nearly 95 per cent,
strength. Beyond this it must be purified by chemical
means, viz., by bringing into it quicklime which abstracts
a quantity of the remaining water. It is again distilled
to free it from the slaked lime. This final product, although
not quite free from water, is the absolute alcohol of com-
merce.
Alcohol 5 is a colourless mobile liquid possessing a pleasant,
ethereal odour and burning taste. It has a sp. gr. of
0-7934 at 61 F., boils at 172-5 F., and does not solidify
until cooled to 267 F. (130-5 C.). Strong alcohol acts
as a poison when taken internally, since it absorbs water
from the system and coagulates albumen. When mixed
with water a contraction in volume takes place ; e.g. if
100 volumes of rectified spirit be mixed with 60 volumes
of water, only 156 volumes of proof spirit are obtained.
Alcohol readily burns in air with a smokeless, almost
colourless flame ; owing to this it may be used in spirit
lamps, as motor spirit and for specially constructed engines.
It is the active constituent of all alcoholic beverages, and
ardent spirits. One of its chief uses depends on its solvent
properties.
THE CARBOHYDRATES
This is the name applied to a group of important food
substances which are composed of carbon and the elements
of water. They are neutral bodies, possessing neither an
aoid nor alkaline reaction, and at the same time although
compounds are not salts.
Although carbohydrates are distributed through the
animal and vegetable kingdoms, there is little doubt as
to their being derived from vegetable sources. A large
number of theories, some based on facts and others on
supposition, have been put forward to explain the formation
of these compounds, but so far none of the theories are quite
satisfactory.
It is generally accepted that the carbon dioxide of the
atmosphere and water in the presence of warmth, sunlight,
60 CHEMISTRY OF BREADMAKING
and chlorophyll form the starting point ; for Sachs, the
celebrated botanist, was able to show that the green
leaves with the above-mentioned materials formed a
condensation product and gave out oxygen.
C0 2 + H 2 O = H.CHO + O 2
Carbon dioxide Water Formaldehyde Oxygen
and 6 C0 2 + 5 H 2 = C 6 H 10 O 5 + 6 O 2
Carbon dioxide Water a-acrose Oxygen
The processes of assimilation probably depend on :
the decomposition of carbon dioxide and formation of
condensation products ; the further breaking up of some
of these latter and recombination to form other bodies ;
the formation of proteids and of the materials from which
carbohydrates are obtained. The assumption that the
carbon dioxide of the atmosphere is insufficient to supply
all the carbon required, and that bicarbonates are taken
up by plant roots and thus assist, is possibly correct.
When formed the carbohydrates are used to build up the
cellulose structure of the plant, while the excess is stored in
the seeds, tubers, bulbs, etc., as a reserve food supply, or to
supply the first food to the young embryo when germination
begins. The great family of the sugars, gums, starches,
and cellulose, commonly known as the carbohydrates,
constitutes a very important group of organic substances
which plays a decisive part in the animal and vegetable
organism, forming a large proportion of its foods and tissues.
Very closely related to the carbohydrates are the alcohols,
many of the higher of which exist free in nature as such,
while the lower ones are obtained by vegetative processes.
Thus mannite, dulcite, and sorbite, white solid alcohols,
exist widely distributed in plant life. If these are gently
oxidised they yield sugars. For example, mannite so
treated forms a glucose-like compound. Conversely, many
of the sugars may readily be reduced back to the alcohol
compound, showing how closely allied the two groups of
bodies are to each other.
Many classifications of the carbohydrates have been put
ORGANIC CONSTITUENTS OF THE CEREALS 61
forward, but none of these are altogether satisfactory.
For simplicity's sake the following will assist in their
study :
Group I. The Monoses.
Group II. The Bioses and higher sugars.
Group III. The Polyoses, or those carbohydrates
which may be converted by hydrolysis into
sugars.
GKOTJP I. THE MONOSES
General formula C 6 H 12 O 6
These include dextrose or grape sugar, Isevulose or fruit
sugar, galactose, and the mixture of dextrose and laevulose
known as invert sugar. The term ' glucose ' is also applied
to dextrose, but it is more suitably given to the mixture of
which dextrose is the chief constituent. Glucose is a
commercial sugar which varies considerably in its com-
position.
The monoses possess the following properties :
All are soluble in water, crystallisable and diffusible.
They are powerful reducing agents, and consequently
readily reduce Fehling's * solution and Trommer's reagent.
They rotate a beam of plane polarised light, and may be
said to possess optical properties. Chemically, they are
either aldehydes or ke tones. All but galactose easily
ferment when brought into solution and mixed with
distillers' or brewers' yeast.
Dextrose or grape sugar, and the glucoses. As its
second name indicates, dextrose is the chief sugar in grapes,
raisins and currants ; it occurs in many other fruits,
especially sweet ones such as cherries, pears, bananas, gener-
ally mixed with an equal quantity of Isevulose ; also in
leaves and roots of plants ; in honey ; in animal fluids as
the chyle, allantoic fluid, blood and urine ; in the liver, in
eggs, etc. It is also obtained as a decomposition product
of vegetable glucosides.
1 Fehling's solution is composed of alkaline copper tartrate.
62 CHEMISTRY OF BREADMAKING
Dextrose may be prepared by the action of acids and
soluble ferments or enzymes on the glucosides ; by the
continuous action of dilute acid on starches and dextrins ;
by separating out the dextrose from raisins or from invert
sugar, or by hydrolysing maltose.
When pure it crystallises in fine, hard needles, which
melt at 295 F. (146 C.). The specific gravity of the
crystals is 1-386, whilst that of a saturated solution at
60 F. (15-6 C.) is 1-221. Dextrose is not charred by
concentrated sulphuric acid except when strongly heated.
It is only about two-thirds as sweet as cane sugar.
A solution of this sugar is, owing to its aldehyde forma-
tion, a powerful reducing agent, precipitating gold, silver,
and platinum from their solutions of salts ; and also
reducing Fehling's and Trommer's reagents to red cuprous
oxide. The solution is dextro-rotatory, that is, it bends
or refracts a beam of plane polarised light to the right
hand. When examined with the aid of a sodium flame,
its rotation is stated thus : the specific rotatory power
(see p. 198) is (a) D +52-8.
3'86
A solution not exceeding fifteen per cent, strength readily
and directly ferments with yeast or yeast-juice.
The glucoses. The name c glucose ' is applied to the
commercial article which is sent into the trade either as a
colourless, very viscid liquid used in the making of fondant,
or as a white or amber to dark-coloured solid. The best
qualities are manufactured from the cereals, especially
maize, starches or from mixtures of these and cassava
starch. Cheap, inferior glucose is prepared from potato
starch. The moist starches are heated under pressure with
dilute sulphuric acid in a converter, the syrup neutralised
with chalk or whiting, then clarified through bone-chars,
and evaporated to the proper consistency in vacuum pans.
For confectionery and cotton-finishing purposes, the
glucose must contain a considerable proportion of dextrin.
This is regulated by the length of time the reactions in
the converter are allowed to continue. For the brewer
ORGANIC CONSTITUENTS OF THE CEREALS 63
not more than about ten per cent, of dextrin is required ;
hence the time is rather longer.
A good glucose should give a clear solution in
water ; should contain no unconverted starch which would
cause a turbidity ; should leave no unpleasant after-
taste in the mouth, and must contain no iron salts
nor free acidity. The colourless variety is obtained by
bleaching a syrup with sulphurous acid or a hydrosulphite
solution.
The glucoses vary considerably in their chemical com-
position, as may be seen from the examples given below.
Constituents.
High
Grade.
Medium
Grade.
Low
Grade.
Potato
Glucose.
Dextrose, .
71-58%
54-567
42-28%
53-56%
Maltose,
7-26,
8-42,
H-47,,
' 7-72,
Dextrine,
8-53,
21-25,
25-65,,
20-34,
Nitrogenous,
0-86,
1 -66 ,
1-52,,
1-84,
Mineral Salts,
0-72,
1-12,
0-85,,
0-34,
Water,
11-05,
12-99,
18-23,,
16-20,
As mentioned above, the various forms of glucose are
used in the preparation of beer worts and priming solutions ;
in manufacturing sweets, confectionery, and table syrups ;
in the adulteration of golden syrup, and in the finishing of
cotton goods.
Lsevulose or fruit sugar or fructose. Laevulose was
discovered by Dubrunfaut in 1847. It occurs in most
sweet fruits together with an equal quantity of grape
sugar.
Laevulose may be prepared by hydrolysing cane sugar
with acid, and separating this sugar from the dextrose by
the insolubility of its lime-compound ; or, better, by
boiling inulin, the starch from dahlia tubers, for about
twenty-four hours with water.
When pure it separates from alcohol in small, hard
yellowish nodules which are much sweeter than
dextrose.
64 CHEMISTRY OF BREADMAKING
The crystals melt at 203 F. (95 C.). This sugar is
more easily decomposed than dextrose by acids and other
reagents. Its solution is a powerful reducing agent, and
is Isevo-rotatory. Its opticity is (<x) D = 95*65. The
copper-reducing power (K) is rather less than that of
dextrose. If the latter is taken as 100, then that of
laevulose is 92-4.
Galactose. This sugar is not known to exist free in
nature, but it is a decomposition product of the group of
gums known as the galactans, and also of lactose or milk
sugar. It is best prepared from gum-arabic by the action
of dilute sulphuric acid, or from the hydrolytic products
of lactose. It crystallises in rhombic crystals which melt
at 320 F. (160 C.). It is readily soluble in water, and
the solution reduces Fehling's solution. This sugar is only
slightly sweet to the taste. Its solutions turn the plane
of polarisation to the right hand, the opticity being
( a ) D = -J-80-3. Chemically it is the aldehyde of inactive
3'86
dulcite, which under ordinary conditions does not ferment
with yeast.
Invert sugar. When pure, this body is a mixture of
equal quantities of dextrose and Isevulose, but owing to
the ease with which the latter sugar decomposes, invert
sugars invariably contain an excess of dextrose. Invert
is a constituent of ripe sweet fruits, cane juices, and of
honey, in which it is mixed up with sucroses, dextrins,
nitrogenous matter, mineral salts, etc. It is used to a
considerable extent as an adulterant of honey.
Inverts are prepared commercially by two processes.
(1) By the action of invertase, one of the soluble ferments
or enzymes in yeast, on a solution of cane sugar. The
sugar solution of about ten to twelve per cent, strength
is brought into a jacketed pan mixed with yeast and
the temperature raised to 131-133 F. (55-56 C.). Yeast
cannot ferment at temperatures much over 110 F.,
ORGANIC CONSTITUENTS OF THE CEREALS 65
but at 132 F. the inverting agent is most vigorous.'
In a short time the whole of the cane sugar is hydrolysed
according to the equation
C 12 H 22 O n + H 2 0=C 6 H 12 6 +C 6 H 12 6
Cane sugar Dextrose Lsevulose
Dextrose Lsevulose
Invert sugar
(2) The more common process is by the action of dilute
acid on the sucroses at a boiling temperature. The
liquors are neutralised with carbonate of lime, filtered and
clarified in bone-chars, then evaporated in vacuum pans.
Inverts as seen in commerce are light to dark coloured
bright-looking syrups, or they may be solid. When pure
and prepared from a good sugar, they dissolve to a clear
solution in water, possess neither acidity nor iron salts,
and do not leave an unpleasant after-taste in the mouth.
They readily reduce Fehling's solution (K = 96'6), and
turn the plane of polarisation to the left hand. The
opticity of pure invert is ( a )D 3 . 86 = 21-30, but that of the
commercial article varies from 16 almost to 0.
Constituents.
High Grade
Invert.
Medium
Grade
Invert.
Low Grade
Invert.
Honey
Pure.
Dextrose,
36-397
35-547
31-72%
39-24%
Lsevulose, .
35-46
34-12,
23-94,,
35-71 ,
Sucrose,
0-61
1-47,
3-00,,
2-69 ,
Intermediate bodies,
7'17
6-53,
18-58,,
2-16,
Nitrogenous,
Mineral salts,
0-52
2-29
1-39,
2-76,
0-69,,
2-21,,
1-28,
0-34,
Water,
17-56
18-19,
19-86,,
18-58,
Traces of
Formic Acid,
etc.
Invert sugars are used chiefly in the brewing industry,
and for the adulteration of honey, and to some extent in
confectionery, but not in breadmaking.
None of the sugars, except the sucroses, and maltose
66 CHEMISTRY OF BREADMAKING
which is present in malt products, are available for bread,
as all others give the crust of the loaf a peculiar reddish
appearance not unlike foxiness. Of the sugars glucose is
the worst in this respect.
GROUP II. THE BIOSES AND HIGHER SUGARS
The more important bioses are the sucroses, maltose, and
lactose. The term ' sucrose ' is used in preference to
cane sugar, as it includes all the sugars possessing similar
properties but derived from different sources, whereas
cane sugar refers to the sugar extracted from the sugar cane
only. The general formula C 12 H 22 O n is applied to each
except when in the crystalline condition. The sucroses
are anhydrous, but maltose and lactose each crystallise
with one molecule of water, hence to them is given the
formula CJ2H22OJJ.H20. The only higher sugar of im-
portance is raffinose (C 18 H 32 6 .5 H 2 0). This occurs chiefly
in such cereals as oats, and in beetroot juice.
The Sucroses (C 12 H 22 O n ).
The word ' sucroses ' is intended to include the sugars
from the sugar cane, sorghum cane, sugar maple, date and
sago palms, sugar beet, chicory, the cereals, and other
sources. The sugar cane contains about eighteen per
cent, of this sugar in the ripe cane juices, while the juice of
the sugar beet contains from fourteen to eighteen
per cent.
Much of the sugar used in the bread and confectionery
trade is obtained from these sources. Beet cultivation
and the extraction of sugar therefrom is confined mainly
to the countries occupying the centre of Europe, viz.,
Germany, France, Austria, and Belgium, and recently in
England.
The growth of the sugar cane is only possible in tropical
regions, especially the West Indies, Peru, Brazil, Central
America, Mexico, Florida, Texas, the Eastern Sea Islands,
as Sumatra, Java, Formosa, etc., Queensland, the Federated
ORGANIC CONSTITUENTS OF THE CEREALS 67
Malay States, and Egypt. The ripe canes possess the aver-
age composition :
Sucrose, . . . . .18-0 per cent.
Fibre, . . . . . 9-5
Water, 71-0
Ash, etc., . . . . 1-5
100-0
The ripe expressed juice has the following average
composition :
Sucrose, 19-2
Other sugars, . . . 0-3
Gums, nitrogenous, . . . 0-7 ,,
Mineral salts, . . . 0-3 ,,
Water, 79-5
100-0
The processes of obtaining the raw sugars may be
summarised as follows :
The extraction of the ripe juices by pressure and diffu-
sion ; the clarification or defecation ; the evaporation of
the juice ; the obtaining of the ' strike ' and the separation
of the sugar crystals from the molasses or uncrystallis-
able sugars. The firsts, seconds, and ' pieces ' sugars so
obtained are then refined to produce the sugars seen on the
market.
Sugar refining. The raw sugars from the cane and beet
are stored separately in a refinery, and when required are
blended in the right proportions, washed somewhat,
dissolved in hot water, boiled down at a high vacuum
(temp. 145-150 F.), crystallised, and passed into the
centrifugals to be separated from the syrup. The sugars
are again dissolved in hot water, and passed through the
animal chars generally downwards ; the clarified syrup is
then boiled in vacuum pans and the various grades of
refined sugars obtained, viz. :
Firsts : in all forms including crystals, super-crystals,
68 CHEMISTRY OF BREADMAKING
granulated, and the cube sugars. Also the milled
sugars as casters and icing, this latter being dressed
with the silks. Most of the ' firsts ' sugars contain
over ninety-eight per cent, of real sucrose. Many of
the granulated run from 99-2 to 99-8 per cent.
Seconds : in all the above forms, but not so pure.
Thirds, fourths, etc., are usually sent out as raw sugars.
The chars, or animal-charcoal filters, consist of iron
cylinders fitted with a perforated false bottom and top.
The whole of the space between is filled with granular
animal charcoal. The active condition of the char is all-
important in obtaining high-grade sugars of all kinds,
including the sucroses, inverts, and glucoses. The action
of the char is probably of a four-fold character : filtering,
oxidising, deodorising, and decolorising.
The animal charcoal itself is prepared by cleansing
bones of horses and cattle, and then destructively distilling
them in iron retorts (just as coal or wood is distilled to
yield coke, ordinary charcoal, and illuminating gas), after
which the charcoal is crushed and graded to the right sizes.
After being continuously in action for from twenty-five
to thirty hours, the contents of the char must be revivified
by heating in the absence of air. This may be repeated
several times, after which the charcoal is useless for further
char work. It is then burned in open grates and used as
bone-ash either for the extraction of phosphorus or as an
artificial manure. The following analysis gives some idea
of the composition of char :
Carbon, ...... 10-91 per cent.
Phosphate of lime, .... 77-58 ,,
Phosphate of magnesia, . . . 0-97
Calcium carbonate, . . . 7*18
Calcium sulphate, .... 0-22
Oxide of iron, alumina, silica, etc., . 1-59
Sulphur and nitrogen compounds, . 1-43
Undetermined, . . . 0-12
100-00
ORGANIC CONSTITUENTS OF THE CEREALS 69
Properties of the sucroses. The sucroses crystallise
from water in hard four-sided monoclinic prisms, which are
soluble in half their weight of water, but only slightly
soluble in spirits of wine. The crystals melt at 320 F.
(160 C.). When heated to nearly 393 F. (200 C.)
they lose water and caramel-like compounds are formed.
The solutions of sucrose are dextro-rotatory, the opticity
being (a) D3 . 86 = +66-5 or (a)^ = +73-8. Sodium flame
readings (a) D X l-1084=white light readings (a) r
The solutions do not reduce Fehling's reagent, nor do
they directly ferment with yeast.
Dilute acid inverts this sugar, yielding invert sugar, as
also does yeast at 133 F. (56 C.).
C 12 H 22 U +H 2 0=C 6 H 12 6 +C 6 H 12 6 .
Sucrose Water Dextrose Lsevulose.
Strong sulphuric acid chars it by abstracting water.
Oxidising agents like nitric acid convert it into saccharic
and mucic acids.
This is the only sugar which can be used with advantage
in breadmaking and confectionery.
Malt sugar, Maltose, Amylon, or Maltobiose
(C 12 H 22 O n .H 2 0)
Maltose was first prepared in the pure state by Dubrun-
faut in 1847, and then forgotten until the late Cornelius
O'Sullivan published -his classical researches on starch
transformations in 1872-76.
It occurs in the commercial glucoses, in worts, beers,
bread, germinated cereals, in the intestinal canal, and
reducing sugars of the blood. It is the important sugar
in malt extracts and diastase pastes.
Maltose may be prepared by the action of diastase,
and all substances containing it, on starch paste or soluble
or malted starch at suitable temperatures, i.e. at about
145 F.
3 C 12 H 20 10 -I-2 H 2 2 C^H^
Starch Water Maltose Dextrin
70 CHEMISTRY OF BREADMAKING
Also by the action of the enzymes of the saliva, and
pancreas, on starch and glycogen (animal starch). Also
by the action of dilute acids on starch, in which case
maltose is an intermediate product.
When prepared pure, maltose exists in fine, white
needle-shaped crystals which lose water when heated to
212 F. (100 C.) and become anhydrous. It is only
moderately sweet but very soluble in water. The solution
readily reduces Fehling's solution, K=61*07. It turns the
plane of polarisation to the right, its opticity being
(a) D =-|-138. Dilute acids and the enzyme maltase
3*86
hydrolyse it to two molecules of dextrose.
C 12 H 22 O n +H 2 0=2 C 6 H 12 O e
Maltose Water Dextrose
Like the sucroses, maltose does not directly ferment.
It is first hydrolysed to dextrose and then readily ferments
with yeast and yeast-juice. The enzyme diastase has no
action on it although it is the agent that produces it.
Maltose is the anhydride of dextrose and probably contains
an unchanged aldehyde group, hence its reducing action on
Fehling's and Trommer's reagents. So far, it has not been
prepared in the pure state on a commercial scale.
Milk sugar, lactose, or lactobiose (CjgH^On.HaO).
Lactose was discovered in 1615 by Fabriccio Bartoletti.
It occurs in varying proportions in the milk of all mammals,
in certain pathological secretions, and in the sap of several
tropical trees, especially the West African cow tree.
Lactose is best prepared from whey in cheese-making
after the separation of the casein.
It forms white, hard, rhombic crystals which melt and
become anhydrous at 284 F. (140 C.). The crystals
possess a faint sweet, gritty taste, and are only moderately
soluble in water, but insoluble in alcohol. The solution
reduces Fehling's reagent, and is dextro-rotatory, its
opticity being (a) D =-j-52-53, or nearly that of dextrose
which is +52-8.
ORGANIC CONSTITUENTS OF THE CEREALS 71
When hydrolysed with dilute acid or the enzyme lactase,
it yields dextrose and galactose :
C 12 H 22 U +H 2 0=C 6 H 12 6 +C 6 H 12 6
Lactose Water Dextrose Galactose
The trisaccharose, raffinose (C 18 H 32 16 .5 H 2 0). This
sugar occurs in several varieties of Australian eucalyptus,
in the flour of cotton-seeds, in the sugar beet, in sugar
molasses, in cereals, etc. From all these sources it may be
prepared.
It crystallises in small needles or prisms possessing
peculiar terminal points. The crystals have only a faint
sweet taste ; are soluble in water, but only slightly so in
alcohol. The solution is strongly dextro-rotatory, its
opticity being (a) J>3 . 86 = +104-5.
When hydrolysed with dilute acid it breaks down first
into fructose (laevulose) and melibiose ; then the melibiose
hydrolyses into dextrose and galactose, thus by hydrolysis
it yields the three common monoses, dextrose, laevulose,
and galactose.
The detection of this sugar in a sample of so-called
cane sugar rather points to the fact that the sample is a
mixture of cane and beet sugars.
GROUP III. THE POLYOSES OR POLYSACCHARIDES
General formula (C 12 H 20 ]0 ) n
This group of carbohydrates comprises the starches,
dextrins, celluloses, gums, pectans, amylans, galactans, etc.
They cannot be called sugars although readily convertible
into such. Not only do they differ from the sugars in their
chemical and physical properties, but they are much more
complex, and their general properties point to a very high
molecular weight.
They are characterised as a rule by their insolubility in
water, their non-crystalline structure, non-diffusibility,
non-fermentability by yeast, and by their not reducing
Fehling's reagent. Two of them, starch and cellulose,
possess an organised structure.
72 CHEMISTRY OF BREADMAKING
The Starches or Amylums (C 12 H 20 ]0 ) n
Starch is widely distributed throughout the vegetable
kingdom, being found in all parts of the green plant ; it
occurs to some extent in animal life as glycogen, a body
also shown to exist in the cells of micro-organisms.
In the growing plant it is formed in the protoplasm of
the chlorophyll granules. From mere points the starch
granules gradually increase in size, until ultimately they
fill up the space and the chlorophyll nearly disappears.
They only continue to grow so long as they are in contact
with protoplasm under suitable conditions of warmth and
light in the presence of carbon-dioxide and water ; hence
starch in leaves must be regarded as an assimilation
product. As fast as this, the raw material of the plant,
is formed it is carried off for various purposes by the plant,
and amongst other things is stored as a reserve food supply,
for example, in the tubers of the potato, dahlia, canna,
cassava, etc., or in the caryopsis (see p. 91) of cereals as in
the cases of wheat, barley, oats, etc.
The structure of the starch granule. When examined
by the unaided eye starch looks like a rather coarse, white
powder, but under a microscope it is found to consist of a
series of stratified concentric layers, the outer ones appear-
ing denser than those near the hilum. 1 From different
sources the granules differ in shape and size, and also
in their behaviour towards physical tests as with polarised
light, selenite plates, and the like (cf. Plates I. and II.).
The outer coating of the granule is considered to be
composed of a kind of starch-cellulose, but this is by no
means certain, while the interior is of starch-flour or granu-
lose. The impervious outer cover protects the granule
and prevents the action of cold water. The granulose is an
intensely colloidal body (see p. 76), and though water may
be absorbed by it, none of it diffuses through the outer
1 The * hilum' is the point or nucleus in a starch granule round
which as an organic centre the layers are arranged.
PLATE I
1
4 6 0* Q * CM"
c
Fig. ll.
r. 12.
Fig. 13. Fig. 14.
STARCHES. (Magnification x 120 diams.)
11. Wheat. 12. Barley. 13, Eye. 14. Eice.
PLATE II
Fig. 15.
Fig. ia
Fig. 17. Fig. 18.
STARCHES. (Magnification x 120 diams.)
15. Oat. 16. Maize. 17. Section of potato tuber with starch
granules in situ. 18. Potato starch (polarised).
ORGANIC CONSTITUENTS OF THE CEREALS 73
cover ; hence starch is said to be insoluble in water. If,
however, the cover be ruptured either by pressure or heat,
the granulose may then be separated from its protecting
cover. The granulose is stained blue by iodine solution,
and the farinose or cover a brownish yellow.
The starch granules from different sources vary con-
siderably in shape and size. Those from tubers are oval
to almost oyster-shell-like in shape, as the potato (Fig. 17)
and canna starches ; cereals yield starches more or less
spheroidal in form, e.g. wheat (Fig. 11), rye (Fig. 13),
barley (Fig. 12), and maize (Fig. 16). Rice (Fig. 14) is an
exception, being very small in size and cornered or angular
in shape.
The extraction of starch from a cereal. For this purpose
the cereal such as wheat or maize should be perfectly ripe
and mature. It is cleaned and separated from all other
seeds, etc., by the processes described in the preparation
of wheat for milling. The cereal is then steeped in water
for two or three days until it is softened. The next step
is grinding between burr-stones with a stream of water
flowing continuously through the feed-hopper so as to carry
the thin paste on to the starch-separators. The starch
passes through the bolt-cloth as a milky fluid, leaving the
husk, germ, and other particles behind. This residue is
passed into the centrifugals to get rid of moisture, then
pressed and sent out as cattle-food.
The milky fluid runs into the wooden settling vats, in
which the starch falls to the bottom, and the clear water is
then run off. The starch is next washed with weak
alkali and thoroughly agitated with it, so as to remove
nitrogenous bodies, fats, and acidity. The washing is
repeated several times ; finally all traces of the alkali are
removed with water, and the starch dried. During the
drying certain impurities come to the surface of the blocks
of starch with the moisture and form a yellowish crust.
This is removed, leaving the remainder as white blocks of
dry starch.
74 CHEMISTRY OF^BREADMAKING
Archbold shows that a bushel of cereal of fifty-six Ibs.
yields about half its weight of starch. Thus
Starch about 50 per cent., . . . 28-00 Ibs.
Dry residue for cattle food, . . . 13-70
Removed during cleansing, . . . 0-73 ,,
Loss during extraction, . . . 7-95
Natural moisture, . . . . 5-62 ,,
Total 56-00 Ibs.
The starch content of the different cereals is given below.
Barley from 52 to 65 per cent.
Wheat 56 69
Rye 51 56
Maize 52 56
Oats 52 57
Rice (hulled) 76 81
Potatoes (tubers) 15 21
The properties of starch. Starch, a white lustrous
powder of specific gravity 1-55 to 1-65, is insoluble in water,
alcohol, ether, and other of the usual solvents. Ordinary
air-dried starch contains from 13 to 18 per cent, of water ;
but, when dried at 212 to 218 F. (100 to 103 C.),
the whole of this is expelled leaving the starch in a very
hygroscopic state. It reabsorbs from 7 to 10 per cent,
of water from the air.
It may be heated to 320 F. (160 C.) without change,
but above this, water of combination is driven off and
chemical action ensues in which dextrins and reducing
sugars are formed. The tuber starches are the most
readily affected in this way, and those of the cereals,
especially rice, the least. The action of hot water is
progressive ; the granulose absorbs water rapidly and
swells until the outer covering is burst, when starch paste
or gelatinised starch is formed. The starches from different
sources gelatinise at different temperatures, potato and
tuber starches between 149-162 F. (65-72 C.), and those
of the cereals between 167-185 F. (75-85 C.).
ORGANIC CONSTITUENTS OF THE CEREALS 75
Dilute acids convert starch into maltose, intermediate
bodies, and dextrins if the action is allowed to continue
for only a short time ; but, if the boiling with acid goes on
for three hours, the starch is converted by hydrolysis into
dextrose :
C 12 H 20 10 +2 H 2 0=2 C 6 H 12 6
Starch Water Dextrose
The action of diastase and its preparations on starch
is of great importance to the baker.
Starch paste is prepared by grinding up some starch with
cold water and then pouring this milky fluid into an excess
of boiling water. Some of this is cooled down to 145 F.
(63 C.), mixed with either diastase paste or some malt
flour or saliva, and allowed to stand for about ten minutes.
According to C. O'Sullivan the starch is transformed into
maltose and dextrin :
3 C ]2 H 20 10 -f2 H 2 O=2 Q^B^OH+C^H^OK)
Starch Water Maltose Dextrin
At higher temperatures the proportions of maltose and
dextrin differ. Diastase does not convert starch into
dextrose or into any sugar lower than maltose. The
maltose may be detected by boiling with Fehling's solution,
in which case red cuprous oxide will be formed. Starch
may be proved to be absent by cooling some of the con-
verted liquid to the ordinary temperature and adding iodine
solution. If starch is absent no blue iodide of starch can
be formed. A baker's scalded flour consists chiefly of
gelatinised starch, and iodine added to some of this cooled
down yields an intense blue colour. If treated with
diastase as above, malt sugar may easily be detected and
starch proved to be absent, because the latter has been
transformed into maltose, intermediate bodies and
dextrin.
When starch is treated with concentrated sulphuric
acid and warmed, water is abstracted and carbon set free,
Just as with any other carbohydrate. Ordinary pure
commercial starch contains from 87 to 92 per cent, of starch,
from 7 to 10 per cent, of water, with traces up to about
76 CHEMISTRY OF BREADMAKINO
0-75 per cent, of nitrogenous matter, fats, reducing sugars,
and mineral salts.
Owing to its colloidal nature and the difficulty of obtain-
ing a clear solution, the molecular weight of starch has never
yet been determined. According to Brown and Morris
soluble starch contains one-fifth of its weight of a dextrin
of formula (C 12 H 20 O 10 ) and molecular weight 6480. There-
fore soluble starch is five times this or 5{(C 12 H 20 O 10 ) 20 }
=32,400. This only goes to prove that granular starch is
an exceedingly complex body of very high molecular
weight.
This so-called soluble starch is a form prepared by treat-
ing granular starch for several days with a dilute solution of
acid. The starch then loses its power of forming starch
paste. It is readily acted upon by diastase.
The form obtained from rice and cassava starches
makes admirable wafer paper, so largely used by the
confectioner.
The Dextrins, Amylins, or Starch Gums (C 12 H 20 O 10 ) n
The dextrins probably consist of mixtures of several or
many isomeric bodies which are colloidal and uncrystallis-
able. The word ' isomeric ' comes from the Greek isos,
equal, and meros, a share or portion. Isomeric bodies are
those composed of the same elements, in the same pro-
portion, but differing in their chemical and physical
properties.
Substances like sugar, salt, and nitre, which when in
solution can pass through a porous membrane like vegetable
parchment, are termed ' crystalloids ' ; whilst bodies such
as starches, dextrins, gums, albumen, gluten, glue, etc.,
which are of a gelatinous nature, are unable to pass through
vegetable parchment, and are termed ' colloids.' Enzj^mes
are reversible colloids, because, if precipitated from their
solution by alcohol, they again dissolve when shaken up
with cool water.
The dextrins are soluble in water and precipitated from
such solution by strong alcohol. This was the method
ORGANIC CONSTITUENTS OF THE CEREALS 77
adopted by C. 'Sullivan in separating maltose from the
dextrins in his work on starch transformations.
Dextrins occur widely distributed in nature in plants,
and to some extent in animal products. They are always
associated with starch or its derived products. In starch
transformations with either acid or diastase, the dextrins
are by-products.
They may be prepared by heating starches alone to
temperatures varying between 338 and 536 F. (170 and
280 C.) , a whole range of dextrins or British gums from white
to yellow and even brown shades of colour being produced.
They may also be obtained by the action of heat and
dilute acids on starches ; or by the action of diastase on
starch paste at a high temperature. All these methods
yield mixtures of dextrins, and other bodies. If continu-
ously heated with dilute acids, the dextrins are transformed
into dextrose or, more correctly, glucose.
Dextrin is prepared commercially by moistening a
mixture of cheap starches with two per cent, strength of
nitric acid, allowing to dry in the air, and then heating
with constant stirring on an iron plate to about 230 F.
(110 C.). This makes a good gum for stamps and adhesive
labels.
During the baking of dough in an oven, some of the
outer crust is converted into dextrins and reducing sugars.
Where steam is used, this mixture of dextrins and sugars
gives the glaze to the surface of the loaf.
The properties of dextrins. The dextrins are gummy,
non-crystalline powders, soluble in water ; these solutions
are dextro-rotatory, the specific rotation being (a) D =
-f-20O4. When pure they do not reduce Fehling's solution,
but most samples contain reducing sugars. They are not
directly fermentable with ordinary yeast, yet a special
species, the schizo-saccharomyces Pombe, contains enzymes
which first hydrolyse and then ferment the dextrins.
Iodine solutions colour solutions of the dextrins either
violet or red, according to the constitution of the com-
78 CHEMISTRY OF BREADMAKING
pounds themselves, whilst one of the dextrins gives no
coloration with iodine solution.
The gums. These are amorphous or non-crystalline,
transparent substances widely distributed through plant
life. When brought into water, they become sticky or
gummy like the dextrins ; some go into solution from
which they may be precipitated by alcohol. These are
the true gums and are distinguished from the wood gums
or vegetable mucilages by the fact that the latter swell up
in water, and do not give a clear solution, as they are
really in a state of suspension. Both groups when boiled
with dilute sulphuric acid yield reducing sugars. Gum-
arabic is a true gum, while gum tragacanth or gum dragon
is a vegetable mucilage.
The Celluloses, Lignoses, or Woody-fibres (C 12 H 20 10 ) n
The celluloses form the principal constituent of the cell-
membranes of all plants, and when examined microscopically
exhibit organised structure, resembling a mass of network
or matted fibre. It is the skeleton form of all vegetable
tissues, such as linen, cotton, flax, hemp, esparto, ramie, etc.
Dragendorff in his work on plant analysis proved that
cellulose from different orders of plants differs in composi-
tion, density, and other factors. Thus, the cellulose from
the phanerogams or flowering plants is readily dissolved
by Schweitzer's reagent, but that from the fungi is either
insoluble or only slightly soluble.
Cellulose forms the framework of all parts of the wheat
plant and other cereals. It is likewise the chief constituent
of bran and other husky materials. As found in nature it
is always associated with gums, resins, sugars, fats, colour-
ing matter, mineral salts, etc. Swedish filter-paper is one
of the purest forms of cellulose found in commerce. Raw
cotton is probably the purest form of natural cellulose,
and from this source it is usually prepared in the pure
state.
It is a white, semi-transparent compound of 1-462
specific gravity, and is insoluble in all the common reagents.
ORGANIC CONSTITUENTS OF THE CEREALS 79
Concentrated sulphuric acid in the cold slowly dissolves
it with much swelling up. If rapidly diluted and boiled,
reducing sugars are then formed.
When unglazed paper is passed through a bath of strong
sulphuric acid several times, then washed thoroughly and
dried, vegetable parchment is obtained. Caustic alkalies
like those of soda and potash modify its structure and
mercerise it. Oxidising agents convert it into oxycellulose
which readily dyes. If treated in the cold with a mixture
of concentrated nitric and sulphuric acids, nitrate of
cellulose gun-cotton, a high explosive is formed.
Collodion is tri-nitro-cellulose dissolved in ether-alcohol
mixture.
Nitro-cellulose and camphor yield a hard gummy mass
known as celluloid, a highly inflammable preparation used
in the manufacture of combs, buttons, and other useful
articles.
ORGANIC ACIDS
A limited number of organic acids occur in the bakery
materials and products. The more important of these are
acetic, butyric, lactic, succinic, and tartaric acids. Organic
acids are classified according to the number of carboxylic
groups they contain. Thus acetic, butyric, and lactic
each contain one of the groups and are therefore termed
mono-carboxylic acids ; whilst succinic, malic and tartaric
contain two and are di-carboxylic acids. Citric is the best
known tri-carboxylic acid. The word carboxylic is a
contraction of carbonyl and hydroxyl and the distinctive
group occurring in the formula of this series of acids is
COOH.
Acetic or the acid of vinegar, and butyric, the acid of
butter fat, both belong to the fatty acids. Lactic is a
member of the oxyfatty acids, and is frequently spoken of
as the * fixed acidity ' of food-stuffs in which it occurs,
because unlike acetic it is non- volatile in steam.
Acetic acid (CH 3 .COOH). Acetic acid is prepared by
two processes : by the destructive distillation of wood,
80 CHEMISTRY OF BREADMAKING
and by the action of acetic bacteria on dilute solutions of
alcohol, especially in low-strength alcoholic beverages such
as clarets, Burgundy, Rhine and Moselle wines (all of
which contain less than twelve per cent, of spirit), ales
and beer, cider and perry, etc.
The alcohol produced in dough by fermentation is oxi-
dised to acetic acid, the smell of which may be recognised
in the steam that issues from the oven during the baking
of bread.
The malt vinegar industry depends on the power of
the various acetic acid groups of bacteria to oxidise alcohol
to acetic acid. The reaction is somewhat complicated,
but may be represented by the equations :
CH 3 .CH 2 OH + = CH 3 .CHO + H 2
Alcohol Oxygen Acetaldehyde Water
and CH 3 .CHO + O = CH 3 .COOH
Acetaldehyde Oxygen Acetic acid
The purest and strongest form is the glacial acetic acid,
a very pungent, acrid-smelling liquid, which produces
white blisters if allowed to touch the skin. The liquid
boils at 2444 F. (118 C.) and has a sp. gr. of 1-080.
It readily mixes with water, alcohol, and ether in all
proportions. This strong liquid forms a good solvent for
many substances that are insoluble in water. The ordinary
acid of commerce contains about thirty-three per cent,
of acetic acid. Such an acid is used in making royal
icing, acetic acid flavouring essences, and for many other
purposes. The amount of this acid in vinegars rarely
exceeds six or seven per cent., which is the strength
obtained by the various vinegar processes.
The salts of the acid are the acetates, and these are of
considerable importance in a number of industries. Verdi-
gris, a basic copper acetate, is formed by allowing thin
copper sheets to stand in vinegar, or when copper vessels
used in jam-making or for sugar-boiling are allowed to
remain dirty after use in contact with air and moisture.
The verdigris forms as a greenish or greenish-blue deposit
on the copper or brass vessels. This copper salt is a strong
ORGANIC CONSTITUENTS OF THE CEREALS 81
poison and therefore ought not to be allowed to come into
contact with foods.
Butyric acids (C 4 H 8 2 ) . The more important of the two
butyric acids is the ordinary or normal butyric (C 3 H 7 .COOH)
which occurs in the free and combined state in nature.
Thus, wherever organic nitrogenous matter and filth are
allowed to collect, bacterial fermentation takes place
resulting in the formation of butyric acid. This is the case
especially during moist, hot weather in dirty, untidily kept
bakerie^ and it leads to the presence of string mould and
other diseases in bread.
Butyric acid in combination with glycerin is the im-
portant volatile fat in butter. When from any cause
this glyceride decomposes, the butter is said to have
become* rancid, because of the nauseous odour of the free
acid. This same acid exists in clothing used in bakeries
and left unwashed for a few days. Stale perspiration on
the person smells equally disagreeably owing to the forma-
tion of butyric acid.
The free acid is a thick liquid, of nauseous odour, which
boils at about 325 F. (162-8 C.). The liquid mixes
readily with water and confers on the mixture its unpleasant
smell. Its salts are the butyrates, the ethereal salts or
esters being used as essences.
Lactic acids (C 3 H 6 3 ). The 'fixed acidity' or lactic
acid of food-stuffs (CH 3 .CHOH.COOH), is formed by the
action of the many different groups of lactic ferments
on carbohydrates in the presence of nitrogenous matter ;
hence it exists in all carbohydrate food-stuffs and beverages,
and in milk. In the free state, it is a thick, sticky, sour-
smelling liquid usually of a brownish colour, although
when pure it is colourless. If dough has been allowed to
over-ferment, and also over-prove, the characteristic
odour of this acid may be observed. It is a common
smell in bakeries where the place and utensils are not kept
scrupulously clean. The organisms which give rise to
lactic acid can be seen if milk is kept for a day or two in a
F
82 CHEMISTRY OF BREADMAKING
warm place and then a drop of the watery liquid examined
under a microscope.
The lactic acid is spoken of as ' fixed acidity ' since, if
distilled with steam, it is not volatile but begins to decom-
pose, whereas acetic acid or ' volatile acidity ' readily
passes over quite unchanged with the steam. The salts
of lactic acid are the lactates, of which the best known
are the lactates of lime and zinc.
CH 2 .COOH
Succinic acid, | . This is the third member of
CH 2 .COOH
the series of di-carboxylic acids. Its chief interest to the
baker lies in the fact that it is formed by the action of yeast
in the dough during fermentation. It is a white solid body
obtained by distilling amber. The salts are the succinates.
CH 2 .COOH
Malie acid, | .Malic is an important fruit
CHOH.COOH
acid, which exists in the free state, and also as its potassium
acid salt in unripe, sharp-tasting, sweet fruits like the
apple (Latin malum, from which it takes its name), rowan
or mountain ash berries, gooseberries, raspberries, black-
berries, grapes, bananas, pineapples, etc., where it is
frequently associated with both citric and tartaric acids.
The free acid is a pleasant tasting compound crystallising
in white, deliquescent, nodular lumps or needles which
easily dissolve in water. Its salts are the malates ; with
the exception of the potassium acid compound they are of
little importance.
CHOH.COOH
Tartaric acid, | . Tartaric acid occurs very
CHOH.COOH
widely distributed in the vegetable kingdom both in the
free state and as its acid salts the tartrates being
generally associated with malic and citric acids. Its chief
source, however, is the deposit of argol that takes place
in the fermentation of grape- juice or must. The argol is
purified and decolorised, yielding the cream of tartar of
ORGANIC CONSTITUENTS OF THE CEREALS 83
commerce. From this the lime tartrate is obtained by
precipitating the solution with a soluble lime salt. The
lime tartrate is now decomposed with sulphuric acid, the
calcium sulphate separated out, and the clear liquors
evaporated to crystallising point. As the work is carried
out in lead-lined vessels, the crystals of tartaric acid
always contain traces of lead. When required for food
purposes, the crystals must be purified and freed from
lead. The crystals are monoclinic prisms which melt at
275 F. (135 C.). When heated strongly they decompose,
forming a number of different compounds, and smell not
unlike burnt sugar at the charring stage.
They possess a very strong acid taste and are some-
what poisonous when taken in quantity. The acid is
readily soluble in hot and cold water, yielding solutions
which possess optical properties and turn the plane of
polarisation to the right hand.
Tartaric acid is used in calico printing and dyeing, in
medicine, and in the preparation of self-raising powders
and effervescing drinks. Its most important salt is the
bitartrate of potassium or cream of tartar. This when
pure forms hard rhombic crystals, which are only moder-
ately soluble in water. The best form for aeration purposes
is the powder, the highest quality of which contains
ninety-eight per cent, of real cream of tartar. When
brought into contact with bicarbonate of soda and water,
Rochelle salt and carbon dioxide are formed. The pro-
portions are approximately two parts by weight of cream
of tartar to one of bicarbonate of soda.
CH.OH.COOH CHOH.COONa
| +NaHC0 3 = | -fC0 2 +H 2
CHOH.COOK CHOH.COOK
Cream of Bicarbonate Rochelle Salt Carbon Water
Tartar of Soda dioxide
CH 2 .COOH
i
Citric acid, CHOH.COOH or C 6 H 8 O 7 . Citric acid is a
I
CH 9 .COOH
84 CHEMISTRY OF BREADMAKING
good example of a tricarboxylic body, yielding three series
of salts somewhat like ordinary phosphoric acid. Citric
occurs widely distributed in nature associated with malic
and tartaric acids and their potassium acid salts. It is
prepared by processes very similar to those used for tartaric
acid. The starting point is the juice from lemons, which
is heated to boiling with chalk and the lime citrate decom-
posed, etc. The acid crystallises with one molecule of
water in hard rhombic prisms. These readily dissolve in
water and alcohol.
The solution possesses a pleasant acid taste not so harsh
as tartaric, and moreover it is not liable to give convulsions
in the stomach as is tartaric when taken internally in
quantity* It is therefore much more suitable for the pre-
paration of aerated beverages. Its salts are the citrates.
THE FATS
The oils or fats, which are so widely distributed through
the vegetable and animal kingdoms, are organic salts
composed of the base glycerin combined with a fatty
acid. They are of two different classes : the volatile fats
which confer flavour and smell on the substances in which
they exist, as, for example, butyrin, one of the chief volatile
constituents of butter ; and the fixed fats which are either
white to yellowish liquids, semifluids, or solids. These
latter possess neither flavour nor aroma except to a very
limited extent, as in the case of the three common fats that
are found in all the cereal oils, lard and margarine, viz., olein,
a yellowish oily liquid, the chief constituent of olive oil ;
palmitin, a white pasty solid found in palm oil and human
fat, and stearin, a white hard solid forming the* bulk of
kitchen grease or tallow.
Glycerin is a trihydric alcohol of the composition
CH 2 .OH
CH.OH
CH 2 .OH
ORGANIC CONSTITUENTS OF THE CEREALS 85
When strongly heated it loses two molecules of water and
forms acrolein, an aldehyde characterised by possessing the
odour of burnt fat :
CH 2 OH.CHOH.CH 2 OH-2 H 2 0=CH 2 : CH.CHO
Glycerin Water Acrolein
A similar reaction takes place in the cooking of flesh-meats,
puff-paste goods, etc., if the temperature of the oven is too
high. Acrolein has an exceedingly pungent and disagree-
able odour.
The more important common fats are btityrin, lauristin,
myristin, olein, palrnitin, and stearin. These are com-
pounds or glycerides composed of the trihydric or tri-acid
base glycerin and the fatty acid that gives its name to the
salt ; thus butyrin, the chief volatile glyceride in butter,
is composed of glycerin combined with three molecules
of butyric acid (C 3 H 7 .COOH).
CH 2 .OH
I
CH.OH +
I
CH 9 .OH
fC 3 H 7 .COOH CH 2 .O.CO.C 3 H 7
C 3 H 7 .COOH=CH.O.CO.C 3 H 7 +3 H 2 O
I
IC,H 7 .COOH CH 2 .O.CO.C 3 H 7
Glycerin Butyric acid Tributyrin Water
The other triglycerides are similarly composed. If these
or any other triglycerides are heated with water at a
pressure, i.e. really superheated steam they are decom-
posed into glycerin and the corresponding free fatty acid.
Example, of palmitin or tripalmitin
CH 2 .O.CO.C 15 H 31 fH.OH CH 2 .OH
I I
CH.O.CO.C 15 H 31 -HH.OH=CH.OH+3 C 15 H 31 .COOH
CH 2 .O.CO.C 15 H 31 IH.OH CH 2 .OH
Tripalmitin Water Glycerin Palmitic acid
Similar decompositions may be obtained by boiling with
water and a small quantity of sulphuric acid.
When any of these natural fats are boiled with caustic
alkalies like caustic soda or potash, or lead hydrate,
the glycerides are broken up into glycerin and the corre-
sponding salt of the fatty acids ; these latter being known
86 CHEMISTRY OF BREADMAKING
as soaps. The ordinary hard or soda soaps are manufac-
tured by boiling mixtures of molten fats first with weak
and then with stronger solutions of caustic soda or soda-lye.
Let X stand for fatty acid, then the reaction may be
expressed by the equation
CH 2 .X (NaOH CH 2 .OH
I I
CH.X + NaOH = CH.OH +3NaX
I I
CH 2 .X iNaOH CH 2 .OH
Triglyceride Caustic soda Glycerine Soda soap
From this it will be seen that the soaps are metallic salts
of the higher fatty acids.
It has already been pointed out that the three glycerides,
olein, palmitin, and stearin, are common to both vegetable
and animal fats ; these occur then in the fats used for food
purposes such as butter, lard, nut or vegetable butter,
margarine, neutral or cotton-seed oil preparations, and
others. The chief point of difference between vegetable
and animal fats is that all vegetable fats contain small
quantities of the solid alcohol phytosterol, while animal
fats contain cholesterol. These may be detected by
preparing their acetates and examining the crystals with
the help of a microscope.
Fats are used in breadmaking as an improver. A small
quantity, two to three ozs. per fourteen Ibs. of flour,
improves the flavour and texture, makes the crust short,
and helps to keep the crumb of the loaf moist. If too
large quantities be employed, it tends to spoil both colour
and flavour, whilst at the same time unduly increasing
the cost.
The natural fat or oil in the cereals exists for the most
part in the germ, to which it gives a yellowish buttery
appearance ; it also saves the germ from being broken up
in the milling process. Wheat oil contains a small quantity
of volatile fat, which rea'dily decomposes and tends to give
the flour a rancid flavour. This is one of the reasons why
millers take out the germ. The chief part of wheat fat,
ORGANIC CONSTITUENTS OF THE CEREALS 87
however, consists of the fixed non-volatile glycerides
olein, palmitin, myristin, stearin, and minute quantities
of others.
The oil itself when refined is a dark yellowish liquid
possessing the characteristic flavour and smell of the
cereal oils. The quantity in wheat varies somewhat
with the different sources ; thus different wheats contain
from 0-90 to 2*71 per cent., English averaging about 1-65.
Whole meal contains from 1-52 to 1-87 per cent. ; standard
meal about 2-03, and patent flours from 0-61 to 1-48 per
cent. Wheat germs contain from 6-56 to 10-31 per cent, of
fat. It is scarcely necessary to point out that the mineral
oils and fats are for the most part hydrocarbons and not
glycerides, therefore they will not saponify, i.e. yield soap
and glycerin when boiled up with a caustic alkali.
THE NITROGENOUS CONSTITUENTS or WHEAT
AND FLOUR
These form one of the most difficult subjects of study,
as, unfortunately, very little of a definite character is
known of these bodies. Most of them, especially the
proteids and gluten, are of unknown composition and
constitution. They are of a colloidal nature, readily
coagulated by heat or very dilute acid ; they combine
with resins and tannins forming compounds, which are
somewhat soluble in sugar solutions but easily thrown out
of solution.
The majority of them, in fact all except the nucleins,
are composed of the elements carbon, hydrogen, nitrogen,
oxygen, and sulphur.
The nucleins contain the five before-mentioned elements
and, in addition, phosphorus and iron.
The nitrogenous bodies may be divided into : the
proteids or albuminoids, including the special proteid or
mixture of proteids known as gluten, which occurs only in
wheat and rye, rendering the meals from these two cereals
fit for breadmaking ; the nucleins, very highly complex
bodies generally found in the nuclei of plants and animals ;
88 CHEMISTRY OF BREADMAKING
and the soluble ferments or enzymes. These latter bodies
will be considered in their proper place in connection with
fermentation.
The proteids are a group of nitrogenous compounds or
mixtures of compounds which are very widely distributed
in plant life, and which when absorbed and assimilated by
animals, act as flesh-forming constituents. They are or
form one of the proximate food principles.
Their mode of formation by plants is to a very large ex-
tent a matter of conjecture. They may be produced by
the combination of either carbohydrate or fatty compounds,
or even the higher alcohols, with simple forms of nitrogenous
compounds absorbed from the soil or air by the plants.
When formed the proteids are stored away, often with
the starches as in the case of the cereals, to act as reserve
food supplies for the embryo during the early stages of
germination. At the proper time, they are degraded by
the action of the proteolytic enzymes into compounds of
a comparatively simple constitution which are soluble,
crystallisable, and diffusible ; hence they may pass by
the processes of osmosis (see p. 125) through the cell-like
structure of the cotyledon into the growing embryo.
The more important proteins of wheat are : leucosin,
an albumin, two or more insoluble proteins, a globulin,
gluten, and possibly proteoses, which latter are decom-
position products.
In the case of the wheat berry, a considerable amount
of the nitrogenous content is found in the aleurone cells.
These form a covering, a single cell in thickness, next to
the starch-containing cells all over the berry, with the
exception of the space occupied by the embryo. This
helps to account for the well-known fact that the lower
grades of flour, which are taken from the wheat berry near
to the bran, contain rather more nitrogen than the patents.
The gluten, or matter which goes to form it, is distributed
throughout the whole of the endosperm probably in the
spaces between the starch-containing cells. If a fine
section of a wheat endosperm be stained first with iodine
ORGANIC CONSTITUENTS OF THE CEREALS 89
solution to colour the starch granules blue, and then with
haematoxylin solution, the spaces between the starch-
containing cells will be of a dark pink shade, showing the
presence of nitrogenous matter, and as all flours contain
gluten in fairly regular proportions from the same wheats,
the inference is that the pink to red colour is due to gluten.
At the present time gluten is considered to be a mixture
of two proteids, viz., glutenin and gliadin.
The glutenin is the constituent which gives strength and
toughness to gluten ; therefore a flour that contains a gluten
in which there is a high proportion of glutenin to gliadin is
a strong flour capable of yielding a loaf of large volume
with little or no flavour.
Gliadin is vegetable gelatin, a soft sticky body which
tones down the strong, harsh glutenin. Flours made from
English wheats contain only a small quantity of gluten,
but this has a relatively high proportion of gliadin ; hence
the small volume of loaf obtained from English wheaten
flours. Such a flour is suitable for blending with a strong
spring wheaten flour, or for cake-making. Both glutenin
and gliadin are looked upon as being composed of a proteid
and an amino-acid. 6
As far back as 1859, Kiihne, Meissner, and others of
the same school of thought showed that the proteids may
be broken down by a series of steps into compounds
becoming less complex at each step, and that the process
closely resembles that of the hydrolysis of starch ; that
dilute acids behaved very much like pepsin or papain in
that the proteids were hydrolysed by these to peptones,
and that the action of alkalies resembled that of trypsin,
in which the proteids were degraded much lower, even to
the form of amides. In more recent times, Osborne,
Chittenden, and other American workers have carried out
a large number of researches on the subject of the cereal
proteids and their derived products.
The amides as a group are soluble, crystallisable, and
diffusible compounds which contain the amino group
The most interesting of these is asparagin,
90 CHEMISTRY OF BREADMAKING
which may be obtained as large, colourless crystals contain-
ing one molecule of water,
CH.NH 2 .COOH
I .H 2
CH 2 .CO.NH 2
Asparagin exists in asparagus sprouts and in cereal root-
lets. It forms an excellent nitrogenous yeast food. Most
of the proteids and their derived products have a per-
centage composition varying between
Carbon Hydrogen Nitrogen Oxygen Sulphur
49-0 6-6 14-9 20-8 0-3
55-2 7-4 18-5 25-3 2-3
The nucleins are much more complex than any of the
proteids, and are mixtures of nitrogenous bodies containing,
amongst other things, phosphorised fat. Their hydrolytic
products form excellent food for plants and animals.
CHAPTER VII
THE CEREALS AND THEIR COMPOSITION
THE cereals or grain-producing plants belong to the great
sub-class Glumaceae of the Monocotyledons. This sub-
class takes its name from the fact that its members have
their flowers arranged inside scaly bracts or ' glumes,'
kinds of husks which protect these minute and delicate
blooms.
The sub-class is further divided into a number of natural
orders or families, and each of these into a genus. The
natural order of the Gramineae or grasses is characterised
by possessing hollow stems, ligules and split leaf-sheaths.
The chief members of this order of plants are : the giant
bamboo, sugar cane, sorghum cane, the cereals including
wheat, barley, maize, oats, rye, and rice, and all the
meadow and wayside grasses. All of these members possess
a number of points in common with one another. The
chief parts of a grass plant are (Fig. 19) :
The tufted roots from which spring a number of hollow
stems, clothed with split leaf-sheaths that are bound to
the stems with a strap or ligule ; the stems divided
into sections by contractions or nodes, and at the head
of the stem a spindle on which is developed first the flower
and finally the ear of corn (Fig. 20). Each little berry is
botanically known as a caryopsis a dry, one-sided fruit
in which the ' pericarp ' and ' testa ' are fused together
into one membrane, the bran. The seed is also
albuminous.
The family name for the wheat plant is Triticum, and
if the plants of this genus be examined they will be found
to possess all the parts of a grass. Again if a wheat
91
92
CHEMISTRY OF BREADMAKING
flower be carefully observed with a strong pocket lens, the
resemblance to the flowers of other grasses is very close
||2fc: Front view of an ear of wheat
Ear viewed
from the side
Ligule
Split leaf
sheath
Node
Tufted
roots
Fig. 19. Drawing of a Wheat Plant to illustrate the Morphology
of Cereals.
(Fig. 21). Both the male and female parts are arranged in
one flower which consists of three stamens growing from
PLATE III
O
Fig. 21. WHEAT FLOWER (highly magnified).
Male parts , anther ; p, pollen grains ; /, filament.
Female parts s, feathery stigma ; o, ovary.
a
.
d,
Fig. -2'2. WHEAT BERRY. Longitudinal section ( x 8 diams.)
(., Embryo or germ.
, Starch.
/>, Endosperm or albumen.
, Bran.
THE CEREALS AND THEIR COMPOSITION 93
below the base of the ovary, hence the flower is hypogenous.
These stamens or male organs are built up of a long hollow
membrane or filament on the top of which is the anther or
hollow box containing the pollen grains. The female parts
Fig. 20. Ears and Grains of three Varieties of Wheat.
are composed of an ovary, the upper portion of which forms
the pistil, this latter being developed into two feathery
stigmas which collect the pollen grains to fertilise the ovary.
The whole of the flower is enveloped inside the protecting
scaly bracts or glumes. A wheat flower in England may
94 CHEMISTRY OF BREADMAKING
best be examined in June and July as in September the
harvest begins.
Classification of wheats. Perhaps the best recent
classification of wheats is that of Professor Dr. Otto Stapf,
who read a very interesting paper on the ' History of
Wheats ' at the Winnipeg meeting of the British Association
in 1909. A summary of this paper is given in an article
on wheats by Dr. Edward J. Russell in No. 18 of Science
Progress, from which the following excerpts are taken.
Wheats are divided into four groups :
(1) Einkorn (Triticum monococcum) ; this has one grain
very compact and bearded on each spikelet. It is the
oldest known wheat and was recently found by
Schliemann in the ruins of Troy ; also in neolithic
remains in Switzerland and Hungary, and it was
known to the Greeks. It is exceptionally resistant to
' rust,' and is still grown in Spain, France, Switzerland,
Germany, and the Balkan States. Stapf found it in
Syria and Upper Mesopotamia, and points out that
the only obvious change between it and Tr. oegilo-
pioides, a wild form, is the much fewer long white
hairs of the spindle as compared with their number in
the wild forms. Other domestic wheats have altered
in the same way.
(2) The second group comprises four classes that are now
very distinct :
(a) The hard or macaroni wheats (Tr. durum).
(b) Emmer (Tr. dicoccum).
(c) The English or Rivet wheats (Tr. turgidum).
(d) Polish wheats (Tr. polonicuiri).
Macaroni wheat has three or four flowers per spikelet,
long bearded ears and hard pointed grains. It is
grown in most of the European countries round the
Mediterranean Sea. Its chief uses are for the manu-
facture of macaroni, and for blending with softer
wheats in milling.
Emmer is a bearded wheat with two grains per spikelet.
It is cultivated in South Germany, Spain, Italy,
THE CEREALS AND THEIR COMPOSITION 95
Servia, Switzerland, India, Abyssinia, Canada, and
the United States of America.
The English or Rivet wheat is another of the cereals of
ancient Egypt. The grains are large in size and
plump, and there may be as many as five per spikelet.
Although of poor quality it yields good crops and is
the commonest bearded wheat in England.
Polish wheat possesses large outer glumes with grains very
long and hard. It is a mutation from Tr. durum.
It gives a poor yield and is grown only in a few districts
other than Italy, Spain, and Abyssinia.
(3) The third group is economically of great importance,
including as it does all the common ordinary wheats,
bearded and otherwise, grown for breadmaking. All
these are grouped under the term Tr. vulgare. The
bearded varieties usually grow best in hot, dry countries,
and the beardless ones in cooler climates.
(4) The fourth group consists of the Spelt wheats. As
in the case of Einkorn, the grains do not readily detach
themselves from the chaff, and hence do not thresh out
like Tr. vulgare. On the northern shores of the Black
Sea there still flourishes a species, Tr. cylindricum,
which seems to have been the original form of the Spelts.
Many of the above classified species and varieties of
wheats are cultivated in the more temperate zones of the
earth, but in England the Triticum turgidum is perhaps the
commonest grown, whilst some Tr. durum or hard macaroni
wheat for mixing purposes, and the varied mutations
known as Tr. vulgare, which include the red and white
Fife wheats and some of the newer and stronger varieties
of the improved French wheats, are also grown.
The strong spring wheats are little grown in England, as
the yields of grain and straw are poor compared with the
turgidum variety, which is a soft one containing a low
proportion of a weak gluten. This latter variety yields
plenty of straw for farm use, whilst the flour from it gives
bread of good flavour.
Both spring and winter-sown wheats are largely grown
96 CHEMISTRY OF BREADMAKING
on the American continent. Other wheats are the Triticum
muticum, also known as Bohemian, Italian, or white wheat,
and Tr. spelta, or the ordinary thin Spelt wheat of France,
South Germany, etc. Tr. durum or hard wheat is largely
grown in Italy owing to the quantity of gluten it contains
approximately 17-0 per cent. and its suitability for
making macaroni, a favourite Italian food. The chief
wheat-growing countries of the world include England,
South and South- West Russia, India, Persia, Hungary,
and parts of Austria, Canada, the United States of
America, Argentina, the southern or cooler portions of
Australia, and New Zealand.
Spring wheats of the Minnesota type yield strong flours
containing much gluten of a tough, elastic kind. Russian,
Indian, and Persian wheats are very hard and dry, with a
fair proportion of gluten. Winter- sown wheats are
generally soft with not too much gluten ; Argentina and
the southern hemisphere wheats belong to this class.
English wheats are about a quarter of an inch long
and one-half that length in diameter. A bushel varies
between 58 and 63 Ibs. in weight with an average of 60 Ibs.
Other wheats than English vary much more in weight ;
thus the heaviest and best European reaches 67 Ibs. per
bushel and the lightest 55 Ibs. Hungarian wheats for
export, by government regulation, must not fall below
60-75 Ibs.
The structure of the wheat berry. If examined ex-
ternally the following points may be noticed (Fig. 23).
The berry is somewhat barrel-shaped ; at the top is a tuft
of hairs the beard ; at the lower end or point of attach-
ment to the spindle on the dorsal or outer side is a small
peculiar-shaped protuberance which indicates the position
of the germ beneath the bran ; on the opposite, inner,
or ventral side is a deep furrow running the whole length
of the grain. This is the crease which harbours a quantity
of dust and micro-organisms, giving rise to difficulties in
the cleaning preparatory to milling the wheat.
In continuance of the examination a section is cut across
THE CEREALS AND THEIR COMPOSITION 97
the grain, viz. a transverse section, so as to permit of an
internal examination of the berry. Beginning from the
outside inwards, if the eye is assisted by a strong pocket-
lens or reading glass, the following parts may be seen :
the outer skins pericarp and testa forming the bran ;
a single layer of rectangular cells full of minute grains of
nitrogenous matter ; these are the aleurone or cereallin cells,
the function of which is to supply the young growing
.Crease
fc _
x Embryo
Beard
Fig. 23. Wheat Berries (magnified).
embryo with its proper nitrogenous food ; and the starch-
containing cells packed full of starch granules of varying
size. The spaces between the cell-walls are probably
filled with the substance known as ' gluten.'
If a longitudinal section (Figs. 22, 24, and 25), that is
one cut from the top to the bottom of the berry through the
embryo and crease, be examined, the following will be seen :
98 CHEMISTRY OF BREADMAKING
the interior of the berry consists of two uneven parts
the major portion or endosperm or albumen, and the small
part at one side near the bottom, which is the germ or
embryo. The germ is protected from injury by a covering
of light wood cells the scutellum ; lying between this and
the endosperm is a row of deep rectangular cells the
absorptive epithelial layer (Fig. 26). In these will be found
the enzymes, which afterwards during germination act on
the constituents of the endosperm, converting them into
foods suitable for the embryonic plant, until it is able to
obtain its sustenance from the air and soil.
In Fig. 24, a are the aleurone cells, b the testa, and c the
pericarp ; the empty starch cells are shown at d, while
at e are a few starch granules that still remain. In Fig. 25
the lower part shows the aleurone cells highly magnified.
In Fig. 26, a is the acrospire, b the plumule, c, d, and e the
root-sheath, rootlet, and root-cap respectively. At / are
starch granules, g are the absorptive epithelial cells, h the
cotyledon, and i the scutellum.
If sections be cut off other cereals, the general arrange-
ment will be seen to conform to that of the wheat berry as
above described. There are, however, sundry points of.
difference. For example, wheat and rye have a single
row of aleurone granules, barley has usually three though
occasionally only two. Wheat possesses a number of fine
hairs at the top of the berry, barley has none, but in most
cases the outer husk or dorsal pale is prolonged into an
awn. When the cereals are ground between hard French
burr-stones into meals, these will be found to contain
particles of the endosperm or starchy matter, mixed up
with hairs, bits of bran, aleurone granules, germ, epidermal
cells, etc.
The chemical composition of the cereals. The cereals
contain the chief proximate principles of food-stuffs, viz.
carbohydrates, fats, proteins, and mineral salts with
water, but not in the proportions to form a perfect food.
This is not of much importance, as they are not relied on
PLATE IV
Fig. 24. Part longitudinal section of a wheat endosperm with
most of the starch granules removed.
Fig. 25. Highly magnified
section through aleurone
cells, showing the granules.
Fig. 26. Section of wheat germ.
THE CEREALS AND THEIR COMPOSITION 99
alone as foods but are always eaten with other food. Bread
is generally taken as bread and butter ; rice with milk ;
oatmeals in various forms with both sugars and milk ;
hence the deficiency in certain of these proximate principles
is made up by the addition of others. As a matter of fact,
the Biblical statement is absolutely true : ' Man does not
live by bread alone.'
If wheat and other cereals are chemically examined,
their composition, although generally similar, differs
considerably in the quantities in which the constituents are
present. But the same cereals, for example the wheats,
differ also very considerably among themselves. Thus
two important constituents, the proteins and carbohydrates,
vary enormously. Dammer in his composition of flour-
wheats as distinct from those used in feeding cattle and
fowls, gives the following figures :
Constituents.
Minimum.
Maximum.
Average.
Water, ....
5-33 /
19-10 7
13-56 %
Proteins, .
8-19
24-16
12-42
Fats,
1-00
,
2-65
1-70
Mineral Salts, .
0-95
2-59
1-71
Cellulose .
1-23
)
6-42
2-66
Starch, sugar, etc.
61-28
77-32
67-89
The author in his experience has also found large varia-
tions not only in wheat and barley, but in other cereals.
The composition of wheats from various sources.
Constituents.
English.
English.
Russian.
Canadian.
Argentina.
Water, .
10-74%
13-56 %
12-77 %
13-97 %
12-29%
Proteins, .
11-98
12-42
17-26 ,,
12-48 ,,
13-12 ,,
Fats,
1-29
1-73,,
1-59,,
1-57,,
1-43 ,,
Mineral Salts,
1-37,,
1-84,,
1-71 ,,
1-73,,
1-58,,
Cellulose,
2-26
2-38
2-13
2-88
2-73,,
Starch, sugars, \
dextrins, gums, /
72-15,,
67-69,,
64-38,,
67-17,,
68-60
Undetermined,
0-21
0-37,,
0-16,,
0-20
0-24
100
CHEMISTRY OF BREADMAKING
The amount of sugars as sucrose in wheats varies between
0-82 and 2-75 per cent.
The composition of cereals other than wheats.
Constituents.
Gold-
thorpe
Barley,
Chevalier
Barley.
Rye.
Maize.
Oats.
Husk less
Rice.
Water,
13-15 %
12-91 7
14-43
I
12-89 /
\ 13-28
:
12-11 %
Proteins,
11-47
12-69 ,
10-37
9-67
\ 14-81
7-62
Fats, .
1-97
2-47,
2-15
>
4-71
4-36
i
0-22
Mineral Salts,
2-48
2-58 ,
1-86
i
1-60
2-71
031
Cellulose, .
7-93
10-51 ,
2-18
2-39
! 11-82
>
0-20
Starch,
59-28
55-68 ,
63-03
j
62-80
49-12
77-25
Sugars (sucroses)
1-63
1-34,
T67
2-63
1-92
5
0-33
Dextrins, gums,
1-68
1-52,
4-03
t
2-9L
1-78
>
1-52
Undetermined,
0-41
0-30,
0-23
>
0-40
0-20
>
0-44
The chemical constituents of the mineral salts. The
constituents of the ash or mineral salts of wheat differ
considerably with the varieties and the soils on which they
are grown. The chief salts are the primary phosphates of
potassium, magnesium, and calcium, there being little
more than traces of other substances. The subjoined
analyses of wheat and barley ash give the student an idea
of their composition :
Constituents.
Wheat.
Barley.
Oxide of potassium (K 2 0), .....
31-47%
0-49
21-26%
2-45 .
Oxide of calcium (CaO), .....
Oxide of magnesium (MgO), ....
Oxides of iron and aluminium (Fe 2 3 and A1 2 3 ),
Phosphoric anhydride (P 2 5 ). ....
2-61
9-57
0-68
53-83
0-67
2-63 .
8-74 ,
0-98 ,
34-79 ,
1-65 ,
Chlorine (Cl )
0-04
0-88 ,
Silica (Si0 2 ),
0-63
26-59 ,
The natural acidity of the wheat berry is due chiefly
to the primary phosphates of the type KH 2 P0 4 . It is
THE CEREALS AND THEIR
also in some measure due to the presence of organic acids,
especially lactic acid, CH 3 -CHOH-COOH.
The germ or embryo of the wheat berry. The germ
(Fig. 26), as previously pointed out, forms a kind of swelling
or excrescence at the lower end of the dorsal or outer side
of the wheat berry. With care it may be excised from its
position, brought on to flannel over a bowl of water, so
arranged that the flannel is kept moist by touching the
water. Given light and warmth the little embryo, which
occupies about a sixtieth of the whole wheat berry, begins
to grow. If examined frequently at the early stages of
growth, much information may be obtained of the germ.
It is somewhat triangular in shape and of a yellowish but-
tery appearance. The germ is rich in nitrogenous matter,
fats, and mineral salts, especially phosphates of potash.
Several groups of enzymes are closely associated with
the germ, the object of these being to prepare the proper
foods for the little plant when germination begins.
Analyses ly the author of 'wheat germs taken from mixed grists.
Constituents.
No. 1.
No. 2.
No. 3.
Uncooked
Hovis germ.
By Mr. Jago.
Water,
12-78%
12-80%
13-41 %
9-43%
13-23%
Proteins (total), .
27-84
28-35,,
29-16,,
30-18,,
/Soluble, 15-51
\Insol., 13-73
Fats, .
6-61
9-32 ,,
9-26 ,,
9-94,,
12-03
Mineral salts,
2-43 ,,
4-10,,
4-22
4-65 ,,
4-94
Cellulose, .
1-97 ,,
2-42
277
3-28
(Dextrin, 1-24
(Maltose, 5 '54
Sugars, gums, ^
dextrins, and j~
48-37
43-01
41-18,,
42-52,,
Undeterd.,33-78,,
undetermined, J
CHAPTER VIII
MILLING, MEALS, FLOURS, AND MALTS
UNDER the heading ' milling ' it is intended to include
not only the actual process of reducing wheat to the
state of finished flour, but also the very necessary and
previous processes the cleaning and conditioning of the
wheats.
The cleaning consists in removing all kinds of foreign
matters such as oats, barley, rye, chaff, large and small
cockle, seeds, stones, string, straw, pieces of metal and
other bodies. Still more is it important to wash or scour
off the dust, beard, and micro-organisms, and the dirt or
soil adhering especially to wheats from hot countries like
India, Persia, the Malay Peninsula, etc.
The conditioning softens the dry, hard, brittle wheats
and brings them into a state suitable for milling. The
usual mode of procedure in a flour mill is to weigh all grain
as it comes in, pass it through a preliminary screening
machine or separator (Fig. 27), and elevate it into the silos
or store bins of the granary. When required, the wheat is
drawn off from the bottom of the silos on to an endless
belt, elevated to the top storey of the cleaning department,
gradually passed from one set of machines to another until
ultimately, at the washing and stoning stage, it has reached
the ground floor. The different types of wheat are cleaned
separately, so that each shall receive the proper treatment
in both cleansing and conditioning.
The cleaning processes may be summarised somewhat
as follows :
The first machine, a separator, consists of a series of
sieves so as to remove large and small bodies from the wheat,
102
MILLING, MEALS, FLOURS, AND MALTS 103
which are carried off in a special channel. The foreign seeds,
about the same size as the wheat berry, are taken out by
means of cockle cylinders. These are rotating cylinders
of special construction (Figs. 28 and 29). From these the
wheat passes into the scourer, which is a kind of revolving
drum fitted with a beater. This by its rapid revolutions
causes the grains to be beaten the one against the others,
and thus hairs, beard, loose husk, soil, and dust are re-
moved. Each of the machines is arranged with an aspirat-
Fig. 27. Section of Receiving or Warehouse Separator.
[By permission of Messrs. Thos. Robinson and Son, Ltd.]
ing current of air to carry off dust. The wheat now reaches
the washers (Fig. 30), where it is further cleansed and
wetted. The very hard wheats require a good deal of
soaking, whilst the medium and soft ones need much less.
During the washing, small stones about the size of the
wheat berry are removed by making use of the difference
in specific gravity between the heavy stones and the
104
CHEMISTRY OF BREADMAKING
comparatively light wheat. The wheats next go to the
centrifugals or whizzers, where surplus moisture is removed,
then down the conditioners to be further dried, and into the
store bins for cleaned wheats where the conditioning is
completed. In a short time the different kinds of wheats
are ready for blending to make up the particular grist of
the mill. Before actually passing into the break rolls
it is necessary to give a dry brushing to remove loose
Fig. 28. Cockle, Oat and Barley Cylinders.
[By permission of Messrs. Thos. Robinson and Son, Ltd.'}
particles and then a slight steaming. The wheat, after all
this preliminary treatment, is then in a fit state to be
milled.
This very complete cleansing of the wheat is an absolute
necessity, not only to prevent speckled and dirty flours,
but also to partially sterilise the flour and thus free it from
noxious organisms. The author has shown by several
researches that, in spite of all this extensive cleaning,
MILLING, MEALS, FLOURS, AND MALTS 105
certain classes of lightly-baked breads are liable to disease
from internal sources, especially when made from low-grade
flours obtained from that portion of the wheat berry near
to the bran.
The plant actually employed in milling proper comprises
break machines for tearing open the endosperm and
liberating the starchy particles ; purifiers to separate the
starchy particles from the bran, germ, and offals generally ;
the reduction rolls which crush the starchy particles or
Fig. 29. Diagram showing internal Construction of Cockle,
Oat and Barley Cylinders.
[By permission of Messrs. Thos. Robinson and Son, Ltd. ]
semolinas into flour ; the silks or flour-dressing machines to
grade and purify the flour ; the bleaching plant ; the possers
for weighing and bagging the finished flour; and the various
conveyors, elevators, and aspirating plants required for
carrying off dust and keeping the various machines cool.
Mr. A. E. Humphries, in a paper read recently before the
Association of Millers, laid down the following as the
necessary factors that wheats should possess in order to
be suitable for milling into present-day flours : Stability,
106
CHEMISTRY OF BREADMAKING
the capacity for making a maximum quantity of bread
from a given weight of flour, and for producing large fine-
textured loaves, of good flavour, with a colour in both crust
and crumb that should be bright in appearance.
The first set of machines in a roller mill (Fig. 31) are the
break rolls. These carry out the operation of breaking up
the endosperm of the berry by a succession of stages varying
from four to seven. The rolls, which are made of steel and
Fig. 30. Section of Double Wheat Washer and Stoner.
[By permission of Messrs. Thos. Robinson and Son, Ltd.
fluted, tear open the berry at its crease, so that in the first
machine the central contents are set at liberty. The
products of this first break, consisting of small angular pieces
from the centre of the endosperm the semolinas break
flour, dust, particles of husk and the remainder of the berry,
are separated by adjustments in the machine, the fractions
passing off in special receptacles, whilst the remnants of
the berry pass into the next break machine where similar
Fig. 31. Cross-section through a Roller Mill.
[By permission of Messrs. Thos. Robinson and Son, Ltd.]
108 CHEMISTRY OF BREADMAKING
operations are conducted, and so on through the whole
series of machines, each time getting nearer to the outside
portion of the berry, until ultimately the bran is scraped
almost entirely free from starchy matter. Any flour
produced in the breaks is separated from the semolinas
and middlings on account of the dust, mainly from the
crease in the berry.
The semolinas, middlings, and dunst, containing brannj;
particles, dust, light feathery refuse or beeswing, etc.,
are passed into the various purifiers so that, as far as
possible, all particles, except the angular starchy pieces, are
taken out. The purified ' throughs ' are then graded into
coarse and fine, and each of these is reduced into flour
separately.
The reduction or grinding rolls (Fig. 32) are quite smooth
and set close, thus working at a pressure. The germ at
this stage becomes flattened by these rolls by reason of its
content of fatty matter and so can readily be removed.
The flour is then dressed by passing through the silk sieves,
which are usually arranged in a kind of revolving cylinder.
Various grades of silk are used, and any particles not
passing through go through the reduction rolls again.
Where no bleaching plant is employed, the finished
flour, after dressing, is weighed and packed by the
power possers, and taken to the flour stores to mature.
The offals are also graded, dressed, and packed by suit-
able machinery.
The bleaching plant used in flour mills is of two types :
the chemical and the electrical. The chemical bleaching
plant consists of the proper arrangement for producing oxides
of nitrogen. These gases are conducted into a kind of
enclosed trough through which the flour is passed by worm
and other conveyors. A few seconds' treatment is sufficient
for the purpose, and great care is necessary to give just the
exact length of time in contact with the gas, since if the
flour becomes overbleached it is practically useless. The
electrical method requires even more care than the chemical,
for the air which has been exposed to the ' fiery blast '
MILLING, MEALS, FLOURS, AND MALTS 109
contains both ozone and oxides of nitrogen. With some
flours even four seconds is too long.
The bleaching of flours assists in their partial sterilising,
ageing, and maturing, as well as rendering the flours a
Fig. 32. Cross-section of Reduction Roller Mill.
[By permission of Messrs. Thos. Robinson and Son, Ltd.]
dead white. The highest grades of flour are not improved
by this treatment, and therefore are rarely bleached.
MEALS AND FLOURS
Meal is the name given to the product obtained by
grinding a cereal between pairs of rolls without separating
110 CHEMISTRY OF BREADMAKING
the offal from the flour. Flour, on the other hand, is
the finely-dressed product in which the separation is as
effective as possible. Flour so prepared is a complex mix-
ture of chemical compounds consisting of carbohydrates,
nitrogenous bodies, fats, vegetable acids, mineral salts,
and water.
Meals contain all the foregoing compounds, and in
addition the bran which includes much more cellulose or
Fig. 33. Modern French Burr-stone Mill or Wholemeals.
woody fibre, fats from the germ, mineral salts, and extractive
matters.
Meals are usually classed as whole, wheat, germ, malted,
and proprietary. For the preparation of the various meals,
specially selected wheats are necessary, and they are best
ground between French burr-stones (Fig. 33), although the
cattle food meals are usually prepared by grinding between
MILLING, MEALS, FLOURS, AND MALTS 111
stones obtained from the mill- stone grit rocks around
Hathersage in Derbyshire and other places. A genuine
wholemeal contains the whole of the materials of the wheat
berry ; frequently, however, the coarsest bran is removed.
The result then is certainly a finer meal that yields a more
palatable and digestible loaf, without a serious loss of the
mineral salts.
Wheat meals differ from the wholemeal in not containing
the whole of the products of the wheat berry. They are
prepared either by separating the germ and some of the
offal, or by mixing together a low-grade white flour with a
certain proportion of offal. These latter may often be
distinguished by the insipid, flavourless bread they yield ;
such a result is largely due to the fact that they are not
ground from selected, suitable wheats of the English type.
Germ meals are prepared in various ways, but one of
the best, and well known in the trade, is made of 75 per
cent, of a good, white flour mixed with 25 per cent.
of cooked germ. The germ is intimately mixed with
the proper quantity of salt for the making of the bread,
and passed by means of worm conveyors through a
steam-heated long cylinder, which effectually cooks and
sterilises the germ. This cooking aids in the keeping
properties of the meal, and at the same time prevents all
enzymic action.
The malted and other meals are so numerous that it
would be impossible to describe them all in the limited
space of a small book. Excellent malted bread may be
manufactured from a good grade of wheat meal thoroughly
mixed with two to three ounces of a diastatic malt flour
for every seven Ibs. of wheat meal, the result being what
is to all intents and purposes a malted meal.
White flours are classified differently in different parts
of the country. The following classification is a common
one and will be readily understood :
Fancy patents made from first break semolinas. Of
these each miller has practically his own speciality,
and it would be invidious to give names of a few of
112
CHEMISTRY OF BREADMAKING
the more largely advertised, seeing that all are high-
class flours.
First patents, which form the best grade of flours
used in making the best bread.
Second patents and superfines, which go for the manu-
facture of medium qualities of bread.
XX, used for common bread alone.
Single X is a mixture of the break flour and the last-
scrapings from the bran. Such a flour is too woolly
and dirty for breadmaking, but is largely employed in the
finishing of calicoes and cotton goods generally.
The subjoined table gives the chemical composition of
some flours and meals :
Constituents.
Patent.
Superfine.
XX.
Whole-
meal.
Reynolds'
Wheat-
meal.
Standard
Flour.
May 1911.
Water,
Proteins,
Fats, .
Mineral Salts, .
Carbohydrates, .
Husky or Fibre, .
Acidity as Lactic,
12-44%
11-23
0-98
0-39
74-67
0-20
0-09
H'87%
12-38 ,,
1'17,,
0-43
73-79
0-22,,
0-14
13-34%
11-09
1-26
0-58
73-29
027
0-17
13-76%
12-53
1-43
1-77
67-63
2-67
0-21
12-00 %
16-40 ,
2-20,
1-50,
66-70 ,
1-20,
12-95%
12-74,,
2-03
0-81
69-86 ,,
1-38,,
0-23
Dry Gluten,
9-72%
H'92%
10-53%
...
'"
THE PROPERTIES OF FLOURS 7
The properties of flour, and it is here intended to apply
the name flour only to the silk-dressed product so as to
distinguish it from the various meals, differ very largely
owing to differences in the formation of grists, the mode of
preparation, and the milling. The most important point
is in the formation of the grist. Each miller selects the
wheats from different sources so as to form a blend or grist
which will yield flours suitable for his trade.
The most important properties of flours are : colour,
strength, absorbing power, and purity.
The colour of flour is a question of the refraction and
MILLING, MEALS, FLOURS, AND MALTS 113
reflection of light. Some flours are a dead white, others a
greyish white, a brownish grey, a yellowish brown, or a fine
creamy yellow shade of colour with a marked bloom. The
latter is the typical colour of a high grade of flour which
frequently has a granular feel to the hand. The different
species and varieties of wheats influence colour. Starchy
and weak wheats like English, and also winter sorts, yield
white flours. Highly glutinous, durum, and strong wheats
generally yield yellowish to dark yellow flours. The very
white or dead-white flours are generally produced by the
action of bleaching. This may be brought about by
exposing a dull grey-looking flour to the chemical
activity of oxides of nitrogen and ozone for a few
seconds ; but the dull appearance of the flour remains
unaffected.
The colour of several flours may be compared either by
means of the well-known Pekar test or by Lovibond's
tintometer.
The Pekar test is carried out as follows : A sheet of
thick plate-glass or a piece of very smooth wood about
four inches wide by twelve in length is required, together
with an ivory or steel flour spatula. A small quantity of
one of the flours is brought on to the plate, pressed tightly
to exclude air-bubbles, brought to one end and the edges
trimmed with the spatula. Another flour is treated
similarly, then brought close to the first sample and the
two carefully pressed and trimmed. Other samples may
be dealt with in like manner. The colours are now com-
pared with the help of diffused daylight, and the various
shades noted. The plate containing the flours is now
brought obliquely into a tank of clean water, passed
through the water in a continuous sweep or curve and
allowed to dry in a cool, airy place. The colours are again
compared, and marked differences in the shades of colour
will be noticed. With a little practice in this work a
student can readily compare the colours of flours. For
night-work a patent Royal Daylight electric lamp should
be fitted up.
H
114 CHEMISTRY OF BREADMAKING
In working with a Lovibond's tintometer, the shades of
colour are determined separately by comparison with glasses
of standard colour, the flour being pressed tightly into small
boxes specially provided for determining the colours of
powders.
The strength of a flour is one of its most important
properties, but up to the present time the various factors
which govern strength are not altogether understood.
W. B. Hardy, F.R.S., has shown that the strength of a
flour is partly dependent on the presence of electrolytes
such as salts, which confer cohesion on the gluten. Dilute
acids and alkalies all tend to break up the gluten into fine
particles ; hence electrolytes confer on glutens its mechani-
cal properties, e.g. its power of holding water ; and these
electrolytes similarly influence the water-holding power
of any other colloid substances present. Some time ago,
the author was able to show that ammonia-free water very
readily disintegrates the gluten, but if alkaline salts are
added the action is at once stopped. Distilled water
partially dissolves gluten, while some is left in a semi-
fluid and sedimentary state without tenacity. Hardy
further pointed out that colloid bodies like moist gluten
possess a sponge-like structure, and that solid particles
decrease the strength of the network structure of gluten by
internal friction, hence washed-out gluten is not quite the
same as gluten in a dough.
The gluten in some flours is strong, tough, and harsh,
as in the case of spring wheats, whilst in others it is weak,
soft, and rather elastic, as in the typical English wheaten
flours. The former type of gluten can much more readily
withstand the friction produced by the starch granules,
especially when the granules are rather small, and is much
more resistant than that in soft wheats. The soft, weak,
and rather elastic form of gluten is one of the causes of the
small loaf produced by English wheaten flours. Flavour
is apparently associated with the gluten, for although the
loaf is small and often of a poor, greyish colour, the flavour
MILLING, MEALS, FLOURS, AND MALTS 115
is of the nutty character and excellent. Spring wheaten
flour yields a large bold loaf, which, however, is absolutely
devoid of flavour. From the foregoing it will be seen that
one of the important factors influencing strength is the
quality rather than the quantity of gluten.
In the section of Chap. XIII. on the nitrogenous con-
stituents of wheat and flour it is pointed out that hot, strong
alcohol dissolves out the vegetable gelatine or gliadin
portion of the gluten, leaving the glutenin in a coagulated
insoluble state, so that the quantity of each may be deter-
mined. If much gliadin is present it tends to make the
gluten become more elastic and softer, but the relation
existing between the glutenin and gliadin does not settle
the question of strength. According to the Local Govern-
ment Board Report of April 1911, the ' strength ' of a flour
is defined as the measure of the capacity of flour for pro-
ducing a bold, large-volumed, well-risen loaf. Bakers use
it to indicate the amount of bread which a given amount of
flour is capable of yielding.
The water-absorbing and retaining power of a flour.
These factors, which are intimately associated with the
' strength ' of a flour, are naturally dependent on the
quality of the gluten, the dryness of the flour, and the
nature and condition of the starch.
A strong, tough, harsh gluten is, as already stated, a good
absorber, or assists in .the absorption of water, but there is
something over and above this. For example, many of
the best, high-milled, Austrian flours possess great absorbing
and retaining powers. This is not due to the harsh char-
acter of the gluten since Austrian flours possess quite a
different character, yet their absorbing power is greater
than that milled from a spring wheat. This is due to one of
those inherent properties of such a flour which is not yet
fully understood.
There is a well-known axiom amongst bakers and millers
that ' a strong flour cannot be milled from a weak wheat.'
What this implies is certainly not completely understood.
116 CHEMISTRY OF BREADMAKING
The dryness of a flour has an important bearing on this
point. As flours are received into the bakery they contain
from 11 to 14 per cent, of moisture. John Blandy's
expression, ' A flour will not absorb more water than it
will nor retain it,' is quite true, yet if the flour be stored
for a few weeks in a dry, warm atmosphere, its absorbing
and retaining powers are considerably increased. The
explanation of this is that the excess of moisture is more
than the flour can carry, or in other words, the quantity
of water in excess of the natural moisture of the flour has
been driven off. This maturing of the constituents of the
flour materially assists its water-retaining power. The
blending of the right flours together also acts in the same
direction. It would be both useful and interesting to a
baker regularly to weigh his flours when they arrive at the
bakery, and also after storing for a week or two. In this
way important and valuable information regarding the
various ' marks ' of flour would be obtained. A writer on
this subject in the early years of the nineteenth century
states that ' the better and older the flour, when properly
stored, the more water it absorbs and retains in baking.
The best flour should absorb nearly three-quarters of its
weight of water, and the worst flour one-half ; whilst the
loss in baking should only be one-tenth.'
Stability. Closely connected with the strength, water-
absorbing, and retaining power of a flour is its stability.
Flours yielding doughs that fall away quickly and drop or
collapse are by no means stable.
This factor, stability, is evidently dependent partly on
the gluten and partly on the material present which can be
used as yeast food. Where there is much of this latter the
yeast will be able to generate large volumes of carbon
dioxide gas ; if now the gluten is strong, tough, and
elastic, so that the gas may be retained and diffused
throughout the dough, there will be little fear of a falling
away and collapse. Although much work has been done
in this direction, very much more is required to enable the
MILLING, MEALS, FLOURS, AND MALTS 117
miller and baker to come to definite conclusions on the
subject of strength and other factors connected with it.
There is yet another point bearing on these questions,
viz. the acidity of a flour. When flours are not suitably
stored, it has been found that the organic acidity increases.
As this change progresses, the gluten and other flour
constituents are degraded and the flours weakened and
deteriorated, which very materially affects the baking
properties of such flours.
The purity of a flour, that is, its freedom from adulterants
of all kinds, is nowadays almost beyond suspicion. Very
rarely indeed are flours found to contain any kind of
foreign starch or other impurity. A few years ago some
French milled flour, containing a fair percentage of talc or
French chalk, was shipped from Marseilles to various ports
in England, and gave rise to a mild scare for a few days.
This flour belonged to the single X grade, and was to be
used for making finish, size, and dextrins for the calico-
printing industry. Apart from similar exceptional in-
stances, flours to all intents and purposes are practically
pure ; in fact, never since the roller-milling industry
became general have our flours been so white, clean, and
pure as at the present time.
For baking and confectionery purposes flours are classed
as weak, medium, and strong. In quick-bread processes,
strong flours are blended with weak or medium ones, so as
to tone down the undesirable properties of the first-named
group of flours; otherwise ungainly, flavourless bread is the
result. Strong flours may be used alone in the setting of
sponges and ferments where the process is to be a long one,
as time is required to mellow and break down the strong,
tough, harsh gluten in such flours. For the doughing
part, medium and soft flours are employed. In the
confectionery department, strong flours are necessary
in the manufacture of nearly all varieties of buns, scones,
and gateaux, for puff-paste of all kinds, tea, girdle, and
barm cakes, etc. Medium flours are more suitable for
intermediate types of smalls, sponge goods, cheap Madeira
118 CHEMISTRY OF BREADMAKING
cakes, and the like. Soft flours are employed for the best
classes of goods of all kinds, especially slab cakes, Christmas,
Easter, Russian, tennis and similar cakes, short paste,
short sweet paste, open and notched tarts, shortbread, and
all the best soft types of biscuits, and many other high-
class goods.
MALTING, MALT FLOUR, AND EXTRACTS
In the early nineties, malt extracts were introduced into
the bakery trade by the French firm, Leconte et Cie,
probably on account of the more general use of American
spring wheat flours in the baking industry. When barms
were commonly used the baker was obliged to know some-
thing of malt, but in these days of progress it is necessary
for him to understand also the process of malting and the
nature of malt products.
Barley, ripe and mature, sound and sweet, is the starting-
point in malting.
After being thoroughly cleaned by dry processes, similar
to those employed in preparing wheat for milling, it is
steeped in cold, hard water at temperatures about 52 F.
for 54 to 72 hours, according to the condition of the barley.
When steeping is complete, the softened grain is allowed
to drain, after which it is thrown into long shallow heaps
to become slightly heated so as to start germination.
The ' couch,' as it is called, is then broken down and the
grain spread out on the growing-floor to form the c first
piece.' It is turned several times to aerate and equalise
both moisture and temperature. During the growing the
barley is worked down the length of the floor so as to
enable other pieces to be worked in regular succession
down the floors. Many changes take place in the grain as
it slowly germinates. The rootlets are developed to about
twice the length of the barleycorn ; the plumule or aero-
spire gradually pushes its way up the back of the corn
beneath the pale or chaff which acts as a protection during
the twelve or more turnings. At the same time, the various
enzymes (p. 125), which exist in minute quantities in the
MILLING, MEALS, FLOURS, AND MALTS 119
cells adjacent to the endosperm, are developed and work
their way upwards towards the opposite end of the corn,
opening up and modifying the interior contents of the
endosperm, or in other words converting it into malt.
For bakery purposes the acrospire should be grown fully
up, as this ensures a high proportion of diastase.
Growing or flooring usually occupies eight or nine days,
after which the 'green malt' is thoroughly withered to check
further growth and dissipate some of the excess moisture
of the grain. The green malt is now loaded on to the kiln,
where it is slowly and completely dried. If any of the
operations are rushed, the malt suffers in a marked way and
becomes unfitted for use. Kilning requires special care,
and in no case is the temperature raised more than about
twenty-five to thirty degrees in twenty-four hours, until all
the moisture has been expelled. When this stage is reached
the draughts of the kiln are closed to prevent the introduc-
tion of fresh air, and the temperature is raised to the curing
point in order to render the malt friable and to give it the
peculiar empyreumatic flavour and aroma.
The cured malt is thrown off the kiln, heaped up, allowed
to cool, passed through the cleaning machinery to take off
the dried rootlets or culms, and then stored for several
weeks to mature.
Malt flour. From such malt, malt flour or diastatic
malt flour is prepared by crushing the malt between fluted
rolls and passing it through sieves to take out the husky
or cellulose matter. The malt being very dry, the husk
breaks up into fine and coarse particles, the latter only can
be removed by the sieves, hence malt flour always possesses
a brownish grey shade of colour. Malt flour freshly
prepared is a very hygroscopic substance, which rapidly
absorbs moisture from the air and soon loses its character-
istic flavour and smell. It ought to be sent out in air-tight
drums instead of in the canvas bags used at present. Brewers,
who are aware of these facts, are careful to keep whole
malt in dry, warm stores until required for use, and only
120 CHEMISTRY OF BREADMAKING
crush the malt a few hours before brewing. Bakers who
stock malt flour in any quantity would be wise to follow the
example of the brewers in this way, as they would then
preserve the fine flavour of the malt and run less risk of the
excess acidity which is so commonly present in slack malts
and badly-stored malt flour.
Malt extracts and diastase pastes. The principal point
of difference between these substances is that in the malt
extracts the diastase has been already used to prepare the
extracts and is therefore present only in small proportions
and weakened ; whereas in diastase paste it is fresh,
vigorous, and active. The extracts are prepared by hot-
water mashing, whilst the pastes are cold-water extractives.
In the manufacture of malt extracts the malt is crushed
between fluted rolls and then mixed with water of such a
temperature that the resultant temperature of the mixture
will be about 145 F., which is the point of maximum
activity for diastase. Every quarter of malt (336 Ibs.)
requires about eleven to twelve hundred pounds weight of
water. The mixture, which has a consistency of thin
porridge, is allowed to stand in the mash- tub for about three
hours so as to ensure the conversion of the starch of the
malt into maltose and dextrins, and to modify suitably
the nitrogenous bodies. This ' wort ' or sugar solution is
run off into a tank, and any sugars remaining in the grains
are washed out by sparging. After settling for a short
time the wort is passed through a filter press, and from
this into another small settler adjoining the vacuum pan.
From this, after some time, the thin liquors pass by suction
into the pan and are boiled down to the proper consistency
afa reduced pressure such that the temperature is between
132-135 F. The thick treacly syrup is now ready
to be run off into the drums in which it is sent out into
commerce. The value of a malt extract depends on the
quantities of malt sugar or maltose, soluble nitrogenous
compounds and mineral salts present. Its chief value lies
in its stimulative effect on the yeast in fermentation.
MILLING, MEALS, FLOURS, AND MALTS 121
Diastase pastes, as previously stated, are cold-water
extracts of malt.
The malt is crushed and made into a thin porridge with
cool water, so that the temperature of the mixtufe is about
70 F. This mash is allowed to stand in the mash-tub
for five hours, so that as much soluble matter as possible is
extracted from the finely divided malt. All the liquor is
run off, and both this and the grains passed through a filter-
press. The liquors are settled and then boiled down in
the vacuum pans as described in the preparation of malt
extracts. Some slight modifications are necessary so that
different strengths of diastase paste may be obtained.
Cheap, low-grade pastes are prepared from inferior bar-
leys and malts ; whilst for the highest grade only the best
barleys, English and foreign, after careful malting, can be
employed.
Diastase pastes depend for their value not only on the
carbohydrates and soluble nitrogenous constituents, but
on the quantity and activity of the diastatic enzymes.
Other soluble ferments or enzymes are present, but they
are of less importance than the diastase. Yet even these
should not be overlooked as they have considerable effect
on the gluten and possibly other substances, resulting
altogether in shortening the time in which the dough is
ready for the oven. Diastase can only act on gelatinised
or soluble starch, therefore the wheaten starch granules
are unaffected by it, but as soon as they become gelatinised
the starch-flour or granulose is at once acted upon and
converted. Wheaten starch granules in presence of
moisture burst or are said to be gelatinised at about
170 F. Diastase action is stopped in the moist state at
176 F., so that it will be seen there is little opportunity
for diastatic action 8 after the dough is in the oven. It is
enougn, nowever, to have a marked effect on the finished
loaf.
Of the three malt products described, diastase pastes
are the best and most useful. The quantities employed
vary from a half to a pound and a half per sack of flour.
122 CHEMISTRY OF BREADMAKING
These quantities, however, may be increased with advan-
tage to from two to three pounds per sack, especially with
strong flours and short processes, without causing extra
difficulties in manipulation. The author found that almost
all grades of bread were very much improved by using
rather higher proportions. Practically all the points of
a loaf were much enhanced. The only question to be
considered is the extra cost to the baker.
The advantages to be derived from the use of diastase
pastes may be summed up as follows :
Externally, the bloom, crust, volume, and the general
appearance of a loaf are all improved.
Internally, the flavour a kind of sweetness is imparted
the appearance of the crumb, and the moisture after
several days' keeping, are all benefited by diastase pastes.
If examined for food value, a malted loaf will be found to
possess many heat-calories more than the ordinary un-
malted bread ; further, such bread is much more readily
digested. Malt flour, which is more easily handled, cannot
be introduced in larger quantities than about a pound to a
pound and a half per sack without spoiling both the external
appearance and the crumb of a loaf. All three classes of
malt products increase the volume and give more spring to
the loaf in the oven.
A high-class, friable malt will yield about 67 per cent,
of extract ; or, in other words, a quarter of malt weighing
three hundredweights should give two hundredweights of
extract.
This extract when used in breadmaking assists in
degrading the flour, feeds the yeast, and so quickens
fermentation.
In the long bread processes it is better to use a diastase
paste in the earlier stages of fermentation and a malt
extract in the later stages.
With strong harsh flours both are invaluable, as they
mellow and tone down the gluten.
Weak flours, which contain a fair proportion of food for
the yeast, do not require these extraneous aids, and, more-
MILLING, MEALS, FLOURS, AND MALTS 123
over, such flours will only be rendered weaker by them.
If they are used the quantity should not exceed four ounces
per sack of flour.
The fluid malt products must be kept in cool places,
otherwise they readily ferment, lose their diastatic power
and maltose, and gradually increase in acidity until they
become sour.
The subjoined analytical results show the difference in
chemical composition of these substances.
The composition of four of the lest types of Diastase Pastes.
Constituents.
1.
2.
3.
4.
Total Solids, ....
75-50%
76-60%
78-25%
78-40%
Water,
24-50 ,,
23-40
21-75,,
21-60,,
Ash (Mineral Salts),
0-95
1-62,,
2-10,,
1-30,,
K. as Maltose,
62-60
64-09 ,,
64-40,,
62-30,,
Dextrin (calculated),
8-11
...
...
4-47
Proteins, etc.,
3-84 ,,
...
10-33 ,,
Specific rotatory power
Diastatic capacity (Lintner),
10-2-8 ,
48
84-85
87
72-2
113
95
102
NOTE. Probably Nos. 2 arid 3 contained added sugar.
Malt Extracts.
Constituents.
1.
2.
3.
4.
Total Solids, .
77-08%
75-12%
78-17%
74-97 %
Water, .
22-92 ,,
24-88 ,
21 83 ,,
25-03 ,,
Mineral Salts,
1-56
1-39,
1-29,,
1*47,,
K. as Maltose,
58-44 ,,
61-26,
62-97
68-22
Dextrin (calculated),
Proteins, etc.,
13-58
3-50 ,,
10-89,
T58,
J13-91,,
5-28
Specific rotatory power
108-1
106-5
97-6
105-8
Diastatic capacity (Lintner),
10
11
16
23
K. stands for Copper reducing power in terms of dextrose =100.
124
CHEMISTRY OF BREADMAKLNG
The composition of some Malt Flours used in the baking trade.
Constituents.
Ordinary
Malt Flour.
Diastase
Malt Flour.
Malt from
English Barley.
Total Solids, soluble in
cold water, .
Moisture, ....
Mineral Salts, .
20-81 %
7-03,,
0-76
9 85
61-60%
4-81
0-78 ,,
4-87 ,
15T)4 %
4-49 ,
0-9(5 ,
8-89
Dextrins, ....
Proteins and other bodies,
Added Sugars (Sucrose), .
Opticity of cold water ex-
tract, ....
Diastatic capacity, .
9-65 ,,
0-55 ,,
33-1
25 (Lintner)
\ 55-95 ,,
58-8
21 (Lintner)
3-15 ,
2-54 ,
117-4
49 (Lintner)
CHAPTER IX
FERMENTS, YEASTS, MOULDS, BACTERIA
UNTIL just recently ferments have been divided into the
soluble or unorganised ferments or enzymes, and the
organised ones including yeasts, moulds, and bacteria.
This classification, in view of published recent research,
can no longer be held, because it has been clearly demon-
strated that the so-called organised ferments can only
bring about fermentation by means of the enzymes con-
tained within the cell-walls.
To understand the subject thoroughly, it is necessary
to possess a knowledge of the behaviour of crystalline and
colloidal substances in regard to vegetable membranes such
as the cell-walls, which enclose the interior contents of
any of the micro-organisms (organised ferments). As
mentioned in Chap. VI. it is only the crystalline bodies
like sugars, amides, and mineral salts that are soluble in
water, which possess the power of readily passing through
vegetable membranes. The process is known as osmosis,
and only soluble, crystalline compounds can pass into the
interior of the cell (endosmosis), or pass out from the cell
(exosmosis). The foods, then, for the organised ferments
must be of this character ; thus the natural sugars of wheat
and flour can so pass into the yeast in dougn-making and
bring about the phenomenon spoken of as fermentation.
Starch, dextrin, and most of the proteids possess a colloidal
structure and therefore cannot undergo osmosis. This
accounts for the yeast being unable to attack and break up
the starch of the flour in bread-making. The very intense
colloid, starch, must first be gelatinised to form starch
paste (scalded flour), then hydrolysed by means of the
125
126 CHEMISTRY OF BREADMAKING
enzyme diastase into maltose (malt sugar), dextrins, and
other bodies. This maltose is soluble, crystalline, and dif-
fusible. It readily undergoes endosmosis, passing into the in-
terior of the yeast-cell where it is acted upon by the enzymes
and converted into alcohol and carbon dioxide, the latter
doing the work of aeration or causing the dough to rise.
The organised ferments or micro-organisms belong to the
great sub-kingdom known as the Cryptogamia. The
members of this division of plants do not reproduce by the
flowering process, hence the name, which means literally
' hidden marriage.' The cryptogams, comprising all non-
flowering plants, are divided into three chief sections and
seven classes. Of these, only the Thallophyta, particularly
class I., need be considered here. The thallous plants
are devoid of all the parts of a true plant, viz. leaves,
stems, roots, and vascular bundles. Class I. of the thal-
lous plants includes the microscopic fungi, i.e. the micro-
organisms or organised ferments. These are devoid also
of the green or brown colouring matter of plants, the
chlorophyll granules.
The micro-organisms for purposes of study may be
divided into the branching fungi and the fission fungi or
bacteria.
The former, designated the Eumycetes, include moulds,
mucors, mildews (oidium), yeasts, torula, and mycoderms ;
whilst the latter group, comprising the whole of the bacteria,
is known as the Schizomycetes.
Bacteria are the smallest of all known living things.
They are unicellular, the cell-wall being composed of
fungi-cellulose a form insoluble in Schweitzer's l reagent
which encloses a mass of fluid protoplasm.
Three shapes of bacteria are recognised :
(a) Spherical or billiard-ball shape e.g. a coccus.
(b) Rod or ruler-shaped e.g. a bacillus such as subtilis.
(c) Spiral or corkscrew-shaped e.g. a spirillum.
Under favourable circumstances all bacteria reproduce
by fission or splitting off, the tw r o parts either separating,
1 Schweitzer's reagent is an ammoniacal solution of copper hydrate.
FERMENTS, YEASTS, MOULDS, BACTERIA 127
or hanging together in chains or clusters. The spherical
forms are the only bacteria capable of splitting up in more
than one direction.
A considerable number form spores inside the parent
cell endogenous spores which possess great refractive
properties and hence they glisten brightly when viewed
under a high-power microscope. Bacilli frequently spore,
but cocci forms do so only very rarely. Another mode of
reproduction is by the continuous development of the rod
lengths, after which fission ensues.
Chemically, bacteria are composed of a covering or cell-
wall of fungi cellulose and internally of an aqueous solution
of a very complex body or mixture of compounds known
as ' protoplasm ' or ' plasma.' According to Von Mohl
(1844) protoplasm is a viscous, tough, elastic, transparent,
and frequently granular, highly active nitrogenous body
built up of carbon, hydrogen, oxygen, nitrogen, and sulphur.
It is probably the most primitive organic substance known,
forming the animate and, so far as can be ascertained, the
ultimate basis or unit of all organic life ; it was defined by
the late Professor T. H. Huxley, F.R.S., as ' the physical
basis of life.'
Cellulose, on the other hand, is what is termed a carbo-
hydrate containing carbon and the elements of water.
It is closely related to cotton and other fibres, paper and
similar substances, but in a number of cases the cell-wall
contains very little true cellulose. Many of the groups of
bacteria either contain or generate a colouring matter, the
pigment Bacterio-purpurin. They exist very frequently
in the many food-stuffs and hence are of considerable
interest to every one taking part in the manufacture of
our daily food.
Some groups possess the power of locomotion, as may be
seen by carefully observing a slide made from almost any
distillery yeast, when as little points of light they may be
seen moving rapidly across the field of view. This motion
of the Bacteria is brought about by means of extremely fine
hairs or whip-like organs termed ' flagella ' ; so fine are these
128 CHEMISTRY OF BREADMAKING
flagella that they can only be detected when suitably stained.
The cocci or spherical forms as a rule are non-mobile.
Irregular forms occur commonly in old cultures, and
render it difficult to recognise the different bacteria by
appearance alone. This irregularity is caused by the
deterioration of the cells : such are the involution forms.
In size bacteria vary enormously, but all are microscopic.
Those occurring in the food-stuffs range between 0*15 //,
and 6 /it in diameter. The symbol JJL (the Greek letter
' mu '), used as the standard of measurement in the study
of micro-organisms, is a thousandth ( 1 O a ) of a millimetre
and is known as a micron.
One metre =39-37079 English inches.
One millimetre= 0-0393708
One micron = 0-000039371
Or yu,= 2 -r^ of an inch.
As the number of bacteria in nature is practically
infinite, it is necessary for the purposes of study to have
some kind of classification other than their shape or form,
which is not by any means an unchanging factor.
A simple and useful classification is that based on the
bacterial action or products formed by their life action :
(1) The Pathogenic or disease-producing Example,
B. typhosus, the Comma bacillus, etc.
(2) The Septic or putrefactive Example, B. subtilis,
lermo, prot'eus groups, etc.
(3) The Zymogenic or fermentative Example, Acetic,
Butyric, Lactic, and other acid-forming groups,
B. Viscosus, etc.
(4) The Chromogenic or pigment-forming Example,
B. Violaceus, which causes blue watery milk,
B. micrococcus, B. prodigiosus, etc.
The members of these various groups all occur in
our ordinary food supplies. For example, water and
milk are carriers of many forms of disease-producing
bacteria, as witness the cholera epidemic in Hamburg
nearly twenty years ago. This was traced to the
town's water-supply taken from the River Elbe con-
FERMENTS, BACTERIA, MOULDS, YEASTS 129
laminated by an encampment of gipsies on its banks.
The outbreak of typhoid in the city of Lincoln quite
recently was also traced to the water supply. Numerous
cases of epidemics may likewise be traced to a contaminated
milk supply.
Putrefactive bacteria occur wherever there is filth in
warm moist places, especially in bakeries which are both
badly arranged and kept in a dirty state. The Zymogenic
bacteria are always present in raw cereal and other foods,
in which they set up acid fermentation.
Suitable media or foods for bacterial growth. The most
suitable nitrogenous foods are soluble proteid degradation
products as peptones, amides, amino-compounds and other
organic bodies, ammonium salts and nitrates of other bases,
whilst in some few cases bacteria are capable of extracting
their nitrogen from the air.
The more available sources of carbon are : carbohydrates
generally, glycerine, fatty acids and the alkaline salts of
many vegetable acids such as malic, tartaric, citric, and
other organic acids.
The mineral foods requisite include the bases : potash,
soda, lime, magnesia, and iron, combined with phosphoric,
sulphuric, silicic, and hydrochloric acids. Of all these
combinations the phosphates are necessary in quantity ;
of the remainder scarcely more than traces are required,
but all must be in a dilute aqueous solution.
Bacteria are either aerobic, anaerobic, or transition forms.
Aerobic bacteria are those which develop and thrive best
in the presence of air ; anaerobic groups flourish in the
absence of air and also of light. The latter are among the
organisms of the septic tank in sewage purification. The
transition forms develop during one portion of their exist-
ence in air, and during another portion in the absence of
air. Acids as a rule act injuriously, and either kill or check
the development of bacteria. B. typliosus, the organism
which is the cause of enteric or typhoid fever, is an exception
to this, since it is capable of converting acid into alkaline
I
130 CHEMISTRY OF BREADMAKING
media. On the other hand, alkalies and alkaline com-
pounds in weak solution act as stimulants to many bacterial
groups.
Light has a similar action to that of acids, and has a
powerful effect in killing or checking bacteria, especially
the pathogenic varieties.
The members of the Schizomycetes group of organisms
require a much higher temperature for their well-being
and to enable them to carry on their life functions, than do
the members of the Eumycetes. These latter can nourish
at temperatures nearly down to the freezing-point of water,
but bacteria can rarely develop when the temperature is
much below 50 F. : hence if milk and such other fluids
as sugar syrups, preserves, etc., are kept cool, they will
remain fit for consumption for considerable periods.
Most of the bakery bacteria develop between 60 and
85 F. Many of the pathogenic germs thrive exceedingly
well about blood-heat, 984 F.
The temperatures suitable for spore formation vary
considerably with the different species, and moreover,
many bacteria require a plentiful supply of oxygen during
the sporulation period.
Electricity and pressure apparently affect the Schizo-
mycetes only very slightly, if at all. A great variety of
products is formed during the life action of these organisms.
Amongst them are hydrogen, nitrogen, carbonic acid, marsh
gas, sulphuretted hydrogen, arsine, alcohols, acids, alkalies,
and such deadly nitrogenous bases as the ptomaines. . The
processes by which these products are formed vary greatly ;
some are the result of fermentation and others of hydrolytic
reactions, whilst some are re-combination bodies.
In order to distinguish between bacteria the following
details should be carefully observed :
(a) The most suitable media or food supplies.
(6) The stages of development and appearance at each
stage.
(c) The products of decomposition.
(d) Their behaviour towards free oxygen.
FERMENTS, BACTERIA, MOULDS, YEASTS 131
(e) The modes and rapidity of multiplication.
(/) The influence of light and temperature.
(g) The action of antiseptics and other re-agents.
(h) Their motility or non-motility.
Bacteria, when grown on the surface of fluid media,
frequently become united, forming a tough gelatinous mass.
In this, the outer mucilaginous coatings cf the organisms
become much swollen and ultimately fuse together, the
bacteria being retained in the mass in quite a regular
manner. Such a condition is known as a Zoogloea or the
Zooglceal state.
All the bacteria found in a bakery must be looked upon
as harmful and disease-producing, and of all none are so
dangerous as the septic or filth groups. Every measure
should be adopted to keep them in check, otherwise serious
consequences may ensue.
The very best means to ensure this freedom is to keep
every part of the bakehouse scrupulously clean. Plenty
of boiling water or steam in all cracks or other places
where organisms may be harboured will, under ordinary
circumstances, be effectual. In the summer time, or when
there is a damp moist heat, the boiling water may be
supplemented by the addition of an antiseptic such as bi-
sulphite of lime, or ' Lustril ' which also acts as a cleansing
agent. These remedies may be still further improved by
using a good system of ventilation. Let all parts of the
bakery as far as possible be light and airy.
For additional information on this subject the following
books may be consulted : Bacteria, by Conn ; Our Secret
Friends and Foes, by Professor Percy Frankland, F.R.S. ;
and the works of Pasteur, Schiitzenberger, Dr. Sims Wood-
head, Professor Franz Lafar, and other writers.
THE HYPHOMYCETES
Hyphomycetes is the name given to a very numerous
group of somewhat highly organised fungi of a parasitic
character that infect and attack both living and dead
bodies. They may be conveniently studied under the
132 CHEMISTRY OF BREADMAKING
divisions oidium, moulds, and mucors ; the first-named are
comparatively simple, while the last group are highly
complex.
In each of these groups are smaller groups or orders,
and these again are subdivided into genera, species, and
varieties. One interesting order, the Mucedines, containing
the genus Peronospora, which genus includes the rusts,
smuts, brands, and mildews that attack most grain-bearing
plants, is perhaps the best known. The mycelial or fine
hair-like threads are branching, thus enabling the members
of the Peronospora genus to develop and penetrate plants
and other food sources in all directions. The spores are
of two kinds, the one carried on the tips of the mycelial
threads and the other kind, which are much larger and
globular in form, borne on the creeping mycelium. The
botanical name for these microscopic plants comes from
a Greek word meaning mildew; thus the Erysiphe and
Oidium groups are plants exceedingly troublesome to the
farmer, owing to their attacks on such of his crops as
the cereals, roots, and fruits.
Another group of the Hyphomycetes is the moulds, also
a numerous group and more highly developed than the
oidium. Many of the members possess the power of induc-
ing fermentation, owing to the enzymes which they secrete,
but from this point of view they are unimportant. The
containing cell-wall of the mycelial threads is of fungi-
cellulose which yields no coloration with iodine solution ;
the protoplasm that fills the cells is free from nuclei, and
contains neither chlorophyll nor starch granules.
The growth takes place by elongation of the cells forming
the hyphae, which latter are subdivided by transverse
diaphragms of cellulose known as septa. The whole of
the mycelium, aerial hyphae or spore-bearing organs and
conidia give rise from a single spore to aggregations
botanioally designated as a ' thallus.'
Moulds can flourish on very concentrated media that
would readily check the development of yeasts and bacteria ;
for example, preserves made with too little sugar are very
FERMENTS, BACTERIA, MOULDS, YEASTS 133
liable to ferment and suffer attacks from the moulds. Some
of them can grow in alkaline solutions, most in neutral foods,
and some few even in acid solutions. Although normally
aerobic, they require only minute traces of free oxygen,
the absence of which induces an alternation of generation
or polymorphism. The ordinary foods containing carbo-
hydrates, mineral salts as in the ash of cereals, and nitrogen
from soluble albuminous compounds, peptones, amides,
amino acids, ammonium salts, and even from nitrates, are
suitable for moulds. Various workers in the study of
mycology have shown that differences in food supply cause
differences in the chemical composition of moulds.
The modes of reproduction :
(a) One of the simplest is by a continuous budding and
dividing off a process closely allied to the budding of
yeasts and their fission. The members of the genus
Oidium reproduce in this way, in fact it is commonly spoken
of as the oidium formation.
(6) By the formation of naked spores or conidia at the
ends of the aerial hyphae or conidia bearers. The Penicil-
lium group, the Eurotiums and subdivisions of these as the
Aspergilli, the Dematiums, the Cladosporia and Botrytis
groups, are all excellent examples of this mode of repro-
duction (Fig. 34).
The mucors, which are more highly organised than the
moulds but which in many ways they very much resemble,
reproduce in two ways : (c) by the formation of spores in a
special receptacle or ' sporangium,' the walls of which burst
when the spores are ripe and allow the contents to escape
and be dispersed in all directions. In some of the mucors
these spores are furnished with cilia or hair-like appendages
which greatly assist in their distribution. The above-
mentioned three modes of reproduction are recognised as
vegetative or asexual processes.
The mucors, however, can also reproduce (d) by sexual
conjugation. Two threads or hyphae join one another
(copulation) and give rise to a large spore or fruit-like body
134
CHEMISTRY OF BREADMAKING
known as a ' zygospore,' from which mycelial threads grow
at a later period after the zygospore has dropped from
the parent mycelium.
The spores produced by any of ttie foregoing methods are
very resistant to desiccation or drying and to large varia-
tions of temperature. They frequently remain dry for
years, but if brought into a suitable food medium at once
begin to develop. All the three groups are well represented
by their various members on our foods or any substances
that contain the necessary food principles. The four
Fig. 34. Penicillium glaucum. From a Microphotograph of a
Mould x 105. I.-V. show the development of a complete thallus
from a single spore. (From a Bottcher moist cell culture.)
commonest are : the ordinary blue mould Penicillium
glaucum (Fig. 34), the sage-green mould Aspergillus
glaucus, Mucor mucedo, and the Oidium lactis. These
induce in our food supplies acidity, decomposition, and
mouldy or musty smells. Damp clothing under similar
conditions also becomes musty and unpleasant-smelling.
YEASTS AND BARMS
The yeasts or Mycomycetes are the botanical names
given to a group of saprophytic fungi so-called because
FERMENTS, BACTERIA, MOULDS, YEASTS 135
they live on prepared foods which play a very important
part in all the fermentation industries, including baking,
brewing, and the manufacture of wines and spirits.
The yeast plant (Fig. 35) consists of a single cell, round
or oval in shape, ranging from five to eleven microns in
diameter with an average of between seven and eight, or
Fig. 35. Colonies of Yeast in Wort-gelatin x 550.
from four- to three-thousandths of an inch in diameter.
This may be expressed in another way : if a line be drawn
exactly an inch in length, then from three to four thousand
of these minute organisms could be placed on such a line.
Each cell is an individual plant surrounded by a thin
transparent dual cell-wall of cellulose and filled internally
with protoplasm. If a cell-wall be ruptured by pressing
136 CHEMISTRY OF BREADMAKING
with a cover-glass or knife blade, the plasma can be readily
stained with a weak solution of methylene blue. Live
protoplasm resists staining in a high degree, but the dead
mass rapidly absorbs this dye. Use is made of this reaction
to detect the presence of dead cells in the yeast employed
by the baker. A slide of the yeast is made in the usual
way, carefully examined by the aid of a compound micro-
scope, then a small drop of the dye solution is brought to
the edge of the cover-glass. In a short time the coloured
liquid becomes dispersed through the cells by the process
of capillarity. This dye has a toxic effect on the yeast
Cell wall
Vacuole containing
a Nucleus
Protoplasm
Fig. 36. Scotch Distillery Yeast. From a
Microphotograph x 1120.
cells, so that the examination for dead and weak cells must
be carried out at once (see p. 150).
Most yeast cells (Fig. 36) develop vacuoles, and inside
of these a nucleus containing that very complex mixture
of compounds, the nucleins. The nucleus is a minute
rounded body which appears to control the activities of a
cell in a manner not yet fully understood. The young
and vigorous cells are rilled with a foamy, highly refractive
form of protoplasm, whilst old cells contain dull-looking,
granular protoplasm which readily separates from the cell
wall. Within recent years, varieties of Saccharomycetes
have been discovered that possess the power of forming true
hyphae, the slender threads of which do not interlace like
those of moulds, hence the yeasts are less complex than the
FERMENTS, BACTERIA, MOULDS, YEASTS 137
Hyphomycetes. These threads must not be confused
with the film forms or pseudo-mycelia of yeasts obtained
when the latter is grown on the surface of a liquid in the
presence of air.
Under normal conditions the yeasts reproduce by the
process of gemmation or budding. The bud is primarily
formed inside the cell itself ; the cell-wall is probably
weakened at this point by enzyme action so that the bud
is able to push its way through, after which it rapidly
develops.
Janssens has shown that both in gemmation and sporula-
Fig. 37. Drawing of Scotch Distillery Yeast from a Microphoto-
graph x 560. The group of cells marked a show sporing. Those
marked b show budding.
tion there is first a division of the nucleus, followed by that
of the protoplasm. The bud thus formed is partially
separated from the parent cell by a cellulosic diaphragm
through which the food supply to the young cell passes.
When the bud has become fully developed it generally
separates itself, but occasionally it adheres, giving rise to a
chain of yeast cells the strepto-formation which often
happens in the case of bakery yeasts, or clusters the
staphylo-form. Some yeasts also reproduce by an abnormal
or starvation process known as sporulation (Fig. 37). This
may be brought about in the laboratory by growing yeasts
138 CHEMISTRY OF BREADMAKING
in sterile water on a gypsum block or on a sterilised slice of
potato. The spores formed in this way are highly resistant
to adverse circumstances, giving the yeast a chance to tide
over periods of stress ; for example, in the wine industry
during the greater part of the year when there are no
grapes, the yeasts exist in this state in the ground, with-
standing the cold and wet of the winter and spring ; later
the dry winds raise clouds of dust and so carry the yeast
spores into the air to settle on the newly-formed grapes.
This statement is not a fanciful one, but a truth backed up
by the splendid researches of the late Professor E. C. Hansen
of Copenhagen and the late Professor Louis Pasteur of Paris.
The spores are enclosed within the sac or mother-cell,
hence they obtain the name ascospores. Hansen made
use of sporulation to differentiate true yeasts from all
others.
There are large numbers of other organisms which closely
resemble the yeasts, as, for example, the torula, organisms
taking the form of groups of minute, spherical, yeast-like
cells. These occur abundantly in all places where sugars,
worts, and musts are prepared, and generally are the cause
of disease. The Saccharomyces apiculatus is a lemon-
shaped yeast which exists in the bloom on fruits ; S. niger,
S. rosaceus, and S. albus were discovered by Professor P.
Frankland in the atmosphere. In addition to these many
other varieties exist, but as none of them sporulate they
cannot be regarded as true yeasts. Sporulation may take
place between the temperatures 34 and 98 F. The
film formation previously mentioned is most successful
between 46 and 51 F.
Suitable media for yeasts. Yeasts can take the carbon
they require from the sugars and other carbohydrates,
but the solutions should not exceed 15 per cent, strength.
The nitrogen is taken chiefly from organic sources as the
peptones, amides, amino compounds and others, whilst
ammonium compounds, with the exception of the nitrates,
are also available. The mineral salts required can be
FERMENTS, BACTERIA, MOULDS, YEASTS 139
ascertained on reference to an analysis of the ash. The
following figures are those of Mitscherlich :
Ash Constituents.
Top Yeasts.
Bottom Yeasts.
Potash (K,0), .
Lime (CaO), .
Magnesia (MgO),
Phosphoric acid (P 2 6 ), .
38-81 %
1-08
6-13
53-91
28-30 %
4-20
8-10
59-40
Nitrous acid and all of its compounds, the nitrites, which
are soluble in water or sugar solution, act as direct poisons
to yeasts. Nitrates and albumenoid ammonia cause rapid
weakening and deterioration, especially in the absence of
free oxygen. Air or free oxygen is a necessity for yeasts.
Most of the great authorities on the study of yeasts, viz.,
Hansen, Lintner, Naegeli, and Pasteur, agree that a small
quantity of free oxygen with 12 per cent, strength of sugar
solutions, are the best mixtures for a vigorous fermentation
with maximum growth and multiplication of yeast cells.
With excess air there is a greater reproduction of cells, but
less fermentation work is carried out.
A trace of acidity, especially that due to organic and
phosphoric acids, assists the yeast cells, and also somewhat
protects them from bacterial competition. Light, except
bright sunlight, electricity and pressure appear to exert
but little influence on yeasts. During the fermentation of
liquids as distinct from doughs, three different periods may
be observed :
(1) The period of rest, during which there is an absorption
of oxygen and a development of the vegetative functions.
(2) The period of activity, during which the sugars are
broken down or hydrolysed, and then fermented to alcohols
and carbon dioxide, with the production of new yeast cells.
(3) The period of slackening, in which the yeast is carried
to the surface of the fermented liquid.
The classification of yeasts and fermentation. Yeasts
140 CHEMISTRY OF BREADMAKING
are classified as the culture yeasts and the wild or disease-
producing ones. The culture yeasts' are those employed
in the bakery, brewery, distillery, and -other fermentation
industries. They may be distinguished from the wild
yeasts by the length of time required in sporulation, by the
large size of the dull-looking spores, and by the less highly
refractive nature of the aqueous protoplasm of the spores.
The wild yeasts are abundant in the vegetable kingdom,
on the skins of the fruits, and in the atmosphere generally,
during the summer and autumn. The spores of these yeasts
are small and more highly refractive than those of the
culture yeasts. Some of the apparatus used in connection
with pure yeast culture is illustrated in Fig. 38.
Yeasts may be distinguished from one another as
follows :
(1) By shape and appearance ; yet the shape of a cell is
dependent on the culture medium, the temperature at
which the culture is made, the age of the culture employed,
and on the presence or absence of air.
(2) By differences in the mode of culture ; thus colonies
of yeasts in wort-gelatine are, in many cases, for the first few
days, perfect spheres, but afterwards they become fringed.
(3) By differences in fermentation, in the fermentation
products and in their behaviour towards media.
(4) By differences in the time and methods of sporulation
and film-forming.
A very large number of different species and varieties of
yeasts have been isolated, their properties, characteristics,
and other factors studied, but up to the present no satis-
factory classification has been drawn up.
For the purposes of our own industry they may very
well be divided into the top fermentation yeasts and the
bottom fermentation yeasts of the culture group. Both
belong to the same genus, Saccharomyces Cerevisiae, but it
has been found impossible to transform the one variety
into the other.
The bottom yeasts vary considerably in size and appear-
ance, in their behaviour towards worts and sugar solutions,
FERMENTS, BACTERIA, MOULDS, YEASTS 141
and in other characteristics. They ferment worts best
at low temperatures, viz., between 38 and 52 F.
Their chief use is in the fermentation of decoction worts
brewed for the preparation of lager beers. Such tempera-
(f)
Fig. 38, Some Apparatus required in Pure Yeast Culture :
a. Freudenreich Flask ; b. Hansen Flask ; c. Petri Dish ;
d. Bottcher Moist Cell ; e. Gypsum Block for Sporulation ;
/. Pasteur Flask.
tures are much too low for the yeasts to be of any great use
in bakery processes.
The top yeasts are therefore the only ones suitable for
general bakehouse work. This group belongs to Saccharo-
myces Cerevisiae I. The word ' Saccharomyces ' comes
from two foreign words, the first part referring to sugar or
142 CHEMISTRY OF BREADMAKING
saccharine bodies, and the latter part to the fungus which
ferments the sugar solutions. The word ' Cerevisiae '
is derived from ' Ceres,' the goddess of corn and wine,
here referring to the sources of the sugars.
A strong, healthy top yeast should possess the following
characteristics :
Uniformity of shape and size, sharpness of the cell-wall
outline, presence of one or two vacuoles with the nucleus
not too distinct, and the absence of foreign matters and
bacteria. The name top yeast comes from the fact that
during fermentation the yeasts produced are carried to the
surface of the fermenting liquid ; the bottom yeasts, on the
other hand, sink to the bottom of the containing fermenting
vessel.
Of the top yeasts, three kinds from different industries
are employed in baking, viz., vinegar, brewery, and
distillery yeasts. Each of these has its own particular
influence on the finished loaf.
The vinegar yeasts always carry with them not only the
aroma of vinegar but also some of the acetic and other
bacteria with which they are associated. In colour,
general appearance and fracture, they are satisfactory,
but as regards flavour and speed of work, vinegar yeasts do
not give the best of results.
Brewery yeasts carry with them their origin. The hop
flavour and aroma is very persistent, even after repeated
washings. The colour is much darker than that of distillery
yeast, and influences the bread by rendering the crumb
darker and dulling the bloom. Further, English brewery
yeasts are accustomed to ferment at temperatures varying
between 57 and 75 F. and at a slow speed. The finished
loaf when prepared with this yeast is smaller in volume,
darker in colour, faintly bitter in flavour, and with a some-
what dull bloom compared with a loaf from a good distillery
yeast, but it is rarely sour.
Distillery yeasts are generally more irregular in shape and
size than brewery yeasts, lighter in colour, possess a pleasant
but different aroma, and are accustomed to rapid fermenta-
FERMENTS, BACTERIA, MOULDS, YEASTS 143
tion at high temperatures ; they are thus in almost every
way the typical yeast for the baker. The chief drawbacks
to the British distillery yeasts are that they contain too
high a percentage of dead cells and far too many bacteria,
whilst many of them are much too variable in their charac-
teristics and properties. These faults are mainly due to
the fact that spirit is the primary object in the distillery,
and yeast is only a by-product. Again, far too large a
proportion of raw grain to malt is employed, thus depriving
the yeast of its proper nutritious food supply. Often the
production of a somewhat inferior yeast is possibly due to
the lack of a suitable scientific training in many of those
in charge of our large distilleries. The advantages of a good
type of distiller's yeast may be summed up as follows :
It is the best all-round type of yeast to use because it
works evenly and is quick, and gives good colour, flavour,
bloom, texture, and volume ; whilst the two chief dis-
advantages are that it is rather more costly and, with care-
less working, there is the risk of acidity and loss of flavour.
The culture of yeast for bakery use. Yeast for the food
industries is either grown in bulk for the yield of yeast
itself, or it is a kind of by-product hi the production of
spirit chiefly whisky.
Abroad, one large factory produces over two hundred
tons of yeast (Fig. 39) per week as its chief product, the
spirit being of secondary consideration.
The writer has only heard of one British firm, with works
near Derby, which devotes itself to yeast manufacture as
its main product. British distilleries 9 produce spirit, while
the yeast is a by-product, hence such yeast cannot hope to
compete with the Continental product with any degree of
real success. Moreover, British brewery yeasts occupy a
similar position in this respect. Again, brewery yeasts
are slow for dough fermentation, since they are accustomed
to develop and work at considerably lower temperatures
than those employed in a bakery.
An account of the production of yeast also involves that
144
CHEMISTRY OF BREADMAKING
of the manufacture of spirit. The proper quantities of
diastatic barley malt and crushed raw grain are intimately
mixed in the proportions of one part of ground malt with
from three to eight parts by weight of the raw cereals,
together with hot water at such a temperature that that
of the mash is about 146 F. During the ' stand on ' of
two or more hours, the enzymes present convert the starches
and other raw materials into wort constituents, such as
Fig. 39. Dutch Yeast. From a Microphotograph x 365.
maltose, dextrins, peptones, amides, and the like. The
sweet wort is run off from the grains ; all remaining constitu-
ents are washed out by sparging ; the mixture of the two is
cooled to about 72 to 75 F., passed through a filter, run
into the large wort becks, and pitched with yeast from a
previous brew. It is very important that the pitching
yeast shall be strong, fresh, vigorous, young cells free from
all forms of contamination. The fermentation goes on
rapidly, as shown by the increase in temperature and the
FERMENTS, BACTERIA, MOULDS, YEASTS 145
attenuation of the wort. In thirty-six hours the highest
temperature of about 82 F. will have been attained ;
then, as the fermentation gradually lessens, the temperature
also falls until a point lower than that of pitching is reached
in, say, another thirty or more hours. During the period
of active fermentation where a large yield of yeast is required,
aeration must be frequent ; at the same time there is a loss
of spirit, hence in British distilleries aeration is not largely
adopted, whilst the temperature is not allowed to go beyond
82 F. on account of the excessive evaporation of spirit.
During fermentation various heads are thrown up by
the yeast ; the first is known as the dirty head, since it is
full of particles composed of little yeast, but much bacteria
and other organisms. This head is skimmed off and
rejected, while the yeast from the succeeding heads is
collected, mixed, pressed, washed, and packed for the use
of the baker. The alcoholic liquid from the fermentation
is ' wash,' which must be filtered, settled, and got into the
' wash stills ' for distillation as quickly as possible in order
to prevent acetous fermentation by bacteria and consequent
loss of spirit. The ' wash ' has a sp. gr. of about 1002 from
a 1042 wort, and contains from 10 to 13 per cent, of proof
spirit by volume. A well-known general rule in distilleries
is : Prepare thin mashes resulting in maltosic worts and
ferment with quick top yeasts to the sp. gr. of water.
BARMS
Barms are of two classes, the virgin and others, which
latter are variously named as Parisian, compound, etc.
The active fermenting principle in all of them is yeast, but
it is mixed up with countless bacteria and other bodies,
most of whick exert an influence on the finished bread.
The effect in the case of the virgin barms is more marked
than in the others, owing to the fact that in the former there
are infinitely larger quantities of acid-forming bacteria in
proportion to the yeast cells than in the latter. At once
it can be seen that barms are suitable only for long processes.
146 CHEMISTRY OF BREADMAKING
Bread prepared by the aid of barms is generally of poor
volume and colour, rather liable to be holey, with dull bloom
and texture somewhat variable, but the flavour as a rule is
good. Barms are suitable for working strong, harsh flours
by long, slow processes. Owing to the large quantity of
bacteria in barms it is customary to use considerably larger
quantities of salt ; thus from four to seven pounds per
sack of flour are not unusual. More than four pounds can
be distinctly tasted ; again, as salt is both an antiseptic
and germicide, too large quantities check the fermentation.
The making of barms. The principles involved and
methods used in making up barms are somewhat as
follows :
Malt is crushed or ground and mixed with a large
volume of water at about 158 to 165 F. so as to give a
thin mash at 145 to 150. The object is to obtain malt
sugar and the proper type of nitrogenous bodies to act as
yeast foods. Whilst this is proceeding, a few ounces of
hops, generally three or four per gallon of water, are infused
in boiling water with stirring so as to extract the various
constituents, viz., the essential oils for flavour, the resins
and tannins for flavouring and antiseptic purposes, and the
other bodies as yeast foods.
With many barms scalded flour is added to the mash to
increase the quantity of sugars. The quantity of a soft
flour is made into a fine batter with either cold water or
some of the wort already prepared, and then the starch
of the flour is gelatinised by pouring in boiling water or
wort, gradually and with Stirring. This scalded flour
batter is either cooled down and added in bulk to the mash
with stirring, or it is added cautiously with continuous
stirring so as not to raise the temperature of the mash
high enough to stop diastatic action. If not above 160 F.
there is little risk. Some bakers use the hop extract for
this purpose. All the ingredients are mixed together and
stirred well, then left for two or three hours to enable
saccharification, or the conversion of the starch into sugar,
FERMENTS, BACTERIA, MOULDS, YEASTS 147
to take place. The sweet- tasting fluid mass is strained and
rapidly cooled to 70 or 80 F.
In the case of a virgin barm, some salt and sugar are
stirred in and the wort left in a cool place for twenty to
thirty hours. In other kinds some barm from a previous
brew, or some distillers' or brewers' yeast, is added to set
up fermentation. During the time such barms are prepar-
ing the tubs should be protected with a loose-fitting cover.
These barms are ready for use in about twenty-four hours.
There are many modifications in the preparation of the
various barms, but the principles involved are the same,
viz., the saccharifying of starch, the addition of hop
extract, and the growing of yeast in the wort prepared.
The alcoholic liquid containing the yeast is then used for
setting sponges and other long processes of fermenting
doughs.
According to the many authorities on this branch of
breadmaking, the following is the comparative value of the
different ferments :
Twelve ounces of distillers' compressed yeast, sixteen
ounces of brewers' compressed yeast, about four fluid pints
of brewers' liquid yeast, twelve pounds of compound barm,
twenty to twenty-four pounds of Parisian barm, or about
thirty pounds of virgin barm are required for each sack of
flour.
THE THEORY OF ALCOHOLIC FERMENTATION
From remote ages it has been known that when sugar
solutions, such as the expressed juices of sweet fruits,
were exposed to the air, the sweetness was gradually lost,
and the liquid took on a spirituous flavour and properties.
During this change it was observed that bubbles were
produced and passed off into the air. It was not, however,
until about 1680 that the cause of the bubbling or boiling
up hence the name fermentation from the Latin ' fervere,'
to boil was discovered. At this period, Antony van
Leeuwenhoek of Delft was working with one of the
first-made compound microscopes and noticed that small
148 CHEMISTRY OF BREADMAKING
spherical bodies were always present in liquids that
* bubbled up ' when cold.
From that time onwards many theories were advanced
to explain fermentation, but none were absolutely success-
ful. The modern or enzyme theory took its rise in the last
half of the nineteenth century from the work of M. Traube.
Even yet very much remains to be done to satisfy every
part of this theory. The following are the names of the
theories displaced by the enzyme or soluble ferment
theory : the mechanical or dead mass theory of Stahl,
Willis, and Liebig ; the amorphous form or catalytic
theory of Berzelius ; the vitalistic theory of Cagniard de
Latour, Schwann, and Kiitzing, and the physico-molecular
theory of Naegeli.
Fermentation is the name given to the process, in which
soluble ferments or enzymes play an important part, by
which the carbohydrates, especially the sugars, are de-
composed mainly into carbon dioxide and alcohol, with
traces of higher alcohols, acids, and other substances.
Although Cavendish and Lavoisier were the first to attempt
an explanation of fermentation, M. Gay-Lussac was the first
to express the reaction by an equation :
C 12 H 24 O 12 = 4 C 2 H 5 .OH + 4 C0 2
Sugars Alcohol (51 '11 %) Carbon dioxide (48 -89 %)
In this equation no account is taken of the higher
alcohols or fusel oils, glycerine, succinic acid, and traces of
other bodies. Yeasts are said to produce alcoholic fer-
mentation whilst bacteria produce the acid fermentation
of carbohydrates, with the formation of such acids as
acetic, propionic, butyric, lactic, and others.
Putrefaction is the decomposition of nitrogenous matter
by bacterial agency accompanied by the production of
noxious gases such as ammonia, sulphuretted hydrogen, etc.
Decay is the slow process by which dry, and also moist,
organic substances are gradually decomposed by the agency
of micro-organisms growing and feeding upon them.
Recent research goes to prove that all the processes of
decomposition may be referred to the action of enzymes,
FERMENTS, BACTERIA, MOULDS, YEASTS 149
and that they are much more complex than was originally
surmised ; for example, the equation of Gay-Lussac was
considered, until within the last few years, to represent
approximately what actually took place during fermenta-
tion ; but when Edward Buchner in 1897-8 published his
researches on yeast-juice and the discovery of the enzyme
zymase, all the previous ideas regarding fermentation were
shown to be wrong. Still later research, dating to May in
the present year (1911), carries the work of the brothers
Buchner much farther. Zymase itself is not sufficient to
induce fermentation of sugar solutions. Dr. Arthur
Harden in his monograph on Alcoholic Fermentation (1911)
conclusively proves that another enzyme, spoken of as a
co-enzyme, and alkaline phosphates are absolutely essential.
The following reactions take place when a sugar is
fermented normally by yeast :
The sugar, if a biose as sucrose or maltose, is hydrolysed
by enzyme action into monoses. These during decom-
position by zymase and its co-enzyme form alcohol, carbon
dioxide, water, other bodies, and a sugar phosphate to
which the name hexose-phosphate has been given. This
compound is hydrolysed by an enzyme hexose-phosphatase
yielding sugar, which is at once fermented. The alkaline
phosphate is then ready once again to re-form hexose-
phosphate, and so the cycle of reactions goes on so long
as any sugar remains in solution.
In accordance with the enzyme theory of alcoholic
fermentation, all decompositions and recombinations
are performed inside the yeast cell itself by the various
enzymes ; therefore all substances passing into the cell
are necessarily of a crystalline and soluble nature, other-
wise they could not diffuse through the vegetable membrane
that forms the cell-wall. The same is true also for all the
excretory products of the yeasts' metabolism. By ' meta-
bolism ' is understood the power that the protoplasm of the
yeast cell possesses of changing the constituents of its food
into other bodies ; whilst the products of this metabolism
are said to be excretory.
150 CHEMISTRY OF BREADMAKING
During the hot season, both the yeast merchant and the
baker experience difficulty in keeping yeast for any length
of time owing to the auto- or self-fermentation of the yeast.
From the work on yeast juice carried out at the Lister
Institute, it would appear that in addition to the substances
before mentioned, the protoplasm also contains a glycogen,
similar to the animal starch found in the liver of animals,
diastase, and proteolytic enzymes. When yeast is exposed
to high temperatures without suitable or sufficient food,
the liquefaction and breaking up of the constituents of the
cell take place, resulting in the annihilation of the yeast.
Yeast may be stored for a considerable period without
deterioration provided that the atmosphere is a dry, cool
one, with a temperature, however, not so low as to freeze
the cells. Recently, a form of desiccated yeast has been
placed on the market in sealed tins for carriage into and
for use in hot climates.
The examination of yeast for bakery purposes. A
general examination of the yeast is first made to ascertain
its colour, taste, smell, appearance, moisture, and the
fracture when a quantity of pressed yeast is broken across.
It is now subjected to a microscopic examination and the
following points noted : the general condition of the yeast
cells as regards regularity in size, a clear strong cell-wall,
whether in a granular state internally, the deterioration
or otherwise of the vacuoles, whether in the budding stage
and the presence or absence of foreign organisms. For
the purpose of this work a small quantity of the yeast is
brought into a small clean bottle, shaken up with sterile
water, a drop withdrawn and put on a micro-slip, then
covered with a very thin cover-glass and examined as above.
Several fields on each of two or three slips should be care-
fully observed and notes made on each. General conclusions
may then be drawn from them.
The presence of dead and very weak cells can be detected
by bringing a small drop of the dye methylene blue to the
edge of the cover-glass, allowing it to work in for a few
FERMENTS, BACTERIA, MOULDS, YEASTS 151
moments and then counting all the cells per field. Next
note all those that are completely stained blue, which are
the dead cells ; then those that are slightly or more stained,
these are the weak cells in which the protoplasm is granular
and the cells shrunken in size.
The gas- evolving power is next determined in the
following way : Five grams of the sample of yeast in as
finely divided a state as possible are accurately weighed,
brought into a glass flask of about two hundred and fifty c.c.
capacity, and ten grams of good cane sugar added ; when
all the fittings are ready, add one hundred c.c. of Avater
at about blood-heat, 98-4 F., insert the cork through
which passes a bent glass tube, the opposite end dipping
under a graduated glass tube, which is suspended with its
lower end just under water contained in a suitable vessel
as shown in the illustration (Fig. 40). The number of
minutes taken for the yeast to begin the evolution of
carbon dioxide gas is noted, after which readings of the
number of c.c. evolved are taken for four or five consecutive
half -hours. The apparatus used for this determination is
a double one, so that a fair average of the gas-evolving power
of the yeast can be obtained.
This determination is usually verified by making a fine
batter with weighed quantities of flour, yeast, and water,
which, of course, will vary according to the size of the
containing vessel employed. The time at which the batter
is set, the length of time taken to come to the highest
point, and the length of time before dropping, are all noted
and comparisons made.
It should be remembered, that if yeast is old and granular
in appearance, if it contains many dead cells and is badly
contaminated with motile and non-motile bacteria, then it
takes longer to begin its vegetative functions, the volume
of gas evolved is low and its evolution slow. Such a yeast
is not fitted for the quick dough processes now in general
use, especially in the towns. Where long-sponge or ferment
methods are still in use, a yeast of the type described may
be much improved by the addition of a pound to two
152 CHEMISTRY OF BREADMAKING
pounds per sack of a good diastase paste or malt extract.
For the quick processes, a very weak yeast would not
recover in time to be of any effective use.
Fig. 40. Apparatus Tor Measuring the Gas-evolving
Power of Yeast.
CHAPTER X
BREADMAKINO PROCESSES AND BREADS
THE earliest of all the breadmaking processes was that in
which leaven was employed ; the leaven itself may be looked
upon as a primeval form of virgin barm, since the active
constituents of this were derived in the first instance from
the atmosphere, like those of the virgin barm. The bread
obtained by the help of leaven was a dark-coloured kind of
cake possessing the usual sweetish-sour taste.
In the present day, two methods of aerating doughs are
in common use : the ordinary process in which one of the
many varieties of yeast forms the active agent, and the
other in which chemical compounds are employed to
generate the carbon dioxide that aerates the dough. Of
these latter compounds one is a metallic carbonate, usually
the bicarbonate of soda an alkaline body although the
normal carbonate, the sesqui, and crystal carbonates all
find use in this direction ; the other compound is either an
acid or hydrogen salt of phosphoric acid, or of some
organic acid like tartaric and citric, or the free acids them-
selves ; e.g. cream of tartar or bitartrate of potassium, or
the potassium acid citrate, or the superphosphate of lime.
The powder most generally used consists of two parts by
weight of cream of tartar mixed with one of bicarbonate
of soda.
When powders are made up in quantity so as to save
time, it is advisable to mix in with them a proportion of
rice or some similar starch, as otherwise the mixture tends
to cake into a hard mass, which gradually gives off its gas
and becomes useless. As an alternative, patent or soda
flour may be made up by thoroughly mixing two ounces of
153
154 CHEMISTRY OF BREADMAKING
cream of tartar (98 per cent, strength) with one ounce of
pure bicarbonate of soda, the two quantities being enough
to aerate four pounds of a strong flour. Brown and certain
special white breads are manufactured on a small scale
with powder. The meal or other flour is rubbed with a
small quantity of fat to shorten and enrich the finished
product, then made into a bay on the working table ; a
smaller proportion of salt than when using yeast, well
crushed to avoid lumps, is distributed over the meal, and
the proper quantity of milk or water at the ordinary
temperature, say 70 F., is brought into the bay, and
the whole worked up into a dough of suitable consistency.
After clearing, the dough is scaled off at the desired weight,
moulded, and allowed to stand for a time to give the powder
a chance to work.
When ready, the goods are baked in a moderately sharp
oven. If the oven is too slow, the goods are dried off
rather than baked ; on the other hand, the oven must not
be too hot, since the generation of gas should be slow and
regular, otherwise the goods are not evenly aerated.
The reaction of the chemicals may be expressed by the
equation :
CHOH.COOH CHOH.COONa
| +NaHC0 3 = | +C0 2 -fH 2
CHOH.COOK CHOH.COOK
Cream of tartar + Bicarbon- = Rochelle salt + gas + water
ate of soda
A smaller quantity of salt is taken than with yeast
because of the Rochelle salt left in the bread. This salt
has a mild purgative action on the human system. If the
alkaline sodium salt is used in excess, the goods are marked
with yellowish-brown streaks and taste of soda. When
cream of tartar is in excess, there is an unpleasant acid
flavour prevalent in the finished goods. All goods made
with powder are very liable to become dry, even when
carefully stored.
A number of mechanical processes have from time to
time been devised and patented for the purpose of aerating
BREADMAKING PROCESSES AND BREADS 155
dough with carbonic acid gas, C0 2 . Amongst these, that
of Dr. Dauglish was the only one to achieve more than a
slight success ; yet, even that survived only for a short time.
BREADMAKING BY AERATION WITH CARBONIC ACID GAS
PRODUCED BY THE ACTION OF YEAST
There are many different methods of aerating or ferment-
ing dough, but in reality only about three of them are in
common use. They are the straight-dough or ' offhand '
process, the ferment and dough and the sponge and dough
methods.
In country districts in England and Wales, and in most
parts of Scotland except one or two of the larger towns,
' sponge and dough ' processes of long duration are still
the order of the day ; but wherever good compressed yeast
can be regularly obtained, straight-dough processes are
becoming more and more prevalent.
Again, in many districts it is still quite common to find
the potato ferment, in spite of its dirt, a usual process of
preparing dough. A potato ferment can be made as
follows : Eight to ten pounds of potatoes of a mealy
character are first well cleaned, then boiled, and, after
standing to dry for a few minutes, pressed through a brass-
wire sieve, mashed with about two gallons of water, and
cooled down to 85 F. Three or four pounds of flour and
eight ounces of yeast are broken up and stirred into the
mash. After standing to ferment for six or eight hours, it
is in a suitable condition for setting a sponge or for making
up by the straight-dough process.
In the Midlands and some parts of the south of England,
a ferment process is employed. This consists in making
a kind of thin batter in the following way :
From one to one and a half pounds of compressed yeast
are well broken up in a gallon of water at 90 F. or at any
temperature up to 98 F. as may be necessary (it should
be noted that yeast is an organism and therefore cannot be
dissolved), and four pounds of flour gradually stirred in to
156 CHEMISTRY OF BREADMAKING
make a fine batter. This ferment should be covered and
put into a warm place until ready, say in about twenty-five
to thirty minutes, when it may be used for a two hours'
sponge process, or for a straight-dough method to be made
into bread in about four hours.
There is also another common way of preparing a ferment
by means of scalded flour and malt, as follows :
Crush or grind ten pounds of malt and mash with three
gallons of water at 160 F. In the meantime infuse
three ounces of hops with a gallon of boiling water for a
short period and cool down the infusion to 145 F.
After the malt infusion or mash has stood for two hours
both this and the hop one are strained together into a barm
tub, pressing out as much of the liquor as possible. Next,
stir in enough strong flour with the strained liquor to form
a thick paste or batter and allow to stand for twelve hours.
Boiling water is now poured cautiously with continuous
stirring into the batter so as to gelatinise the starch. The
malt soon liquefies the scalded flour, as may be observed
by the gradual thinning down of the batter.
Half a gallon of the thin batter is used per sack of two
hundred and eighty pounds of flour, for making a sponge
(one-third water), which is to stand for eight or ten hours.
Generally, from eight to twelve ounces of good distillery
yeast will be required with such a batter.
The sponge and dough bread process. The sponge
process is still the prevalent one, though it is fast being
superseded by the straight or offhand method. A sponge
and dough process is in reality an operation to make dough
in two stages, viz., the setting of the sponge and the
doughing up. Several different sponges are used, the
quarter, the third, the half, and the three-quarter ; whilst
the length of time may range from two to twelve or more
hours. Anomalous though it may appear, there is less
risk of acidity in the finished bread with a long than with
a short sponge. In long-period sponges, the temperatures
are kept fairly low and a proportion of salt is used, both
BREADMAKING PROCESSES AND BREADS 157
conditions being inimical to lactic and other bacteria ;
hence long sponge-made bread other conditions being
equal generally eats sweet. Short processes require less
salt and a higher temperature, consequently the correspond-
ing risks are greater.
One of the chief advantages of a sponge process is that
the actual sponge is a thin medium containing all the chief
essentials for the growth of yeast, and is of such a con-
sistency that the yeast actually increases in quantity.
This permits of the use of a rather less weight of yeast per
sack of flour than is required in a straight-dough process,
thereby effecting a considerable saving in the course of a
year.
Sponges were stated to be quarter, third, half, and three-
quarter ones. By this is meant that in setting the sponge,
approximately one quarter, or a third, etc., of the water
would be used in this operation, the remainder at the
proper temperature being added at the doughing stage of
the proceedings.
Sponges are also spoken of as ' twelve hours' sponge ' or
other period down to as short as a ' two hours.' The time
stated is intended to include that occupied for all operations
until the dough is ready to be scaled off and available for
making up and proving. In bakeries where the one dough
follows the others in a regular succession it is necessary that
the quantities of the ingredients, their temperatures and
the resulting doughs and times of each, should be accurately
gauged and strictly followed throughout. Each and
every operation must be carried out with the greatest
punctuality and regularity. These are two out of four of
the essentials in a bakery, the other two being cleanliness
and the absence of wastefulness, i.e. economy.
To enable the baker to fix the correct times for a succes-
sion of doughs he ought to know the following points :
(1) The temperatures of the flour, liquor (water), and the
bakehouse.
(2) The characteristics of the yeast or barm to be used.
(3) The approximate composition of any yeast food or
158 CHEMISTRY OF BREADMAKING
bread improver which it is proposed to add to the yeast
and flour.
(4) The character and type of flours to be employed.
For example, bread improvers of the mineral sort, contain-
ing, say, gypsum or calcium sulphate, act as antiseptics
and retard fermentation ; fats when used in excess behave
similarly ; malt products, on the other hand, all act as
stimulants to the yeast in addition to improving the
finished loaf. There are on the market one or two of the
mineral improvers based on Pasteur's method of preparing
pure yeast, which, owing partly to the fact that they prevent
bacterial competition and partly that they contain phos-
phates, are actually stimulants to the yeast in addition to
being bread improvers.
The temperatures of the bakehouse and of the chief
ingredients are of the utmost importance.
If the temperature of the sponge is low and that of the
bakehouse also low, then for a given consistency the
reactions going on in the sponge will be slow ; if the tempera-
ture of the sponge be increased, then the changes will
become accelerated and the time shortened.
The flour should be stored in a dry, warm atmosphere,
as this condition of things causes an improvement in the
flour in most cases and also prevents a chilling of the yeast
whereby its vital functions are checked.
The temperature of the bakehouse can be ascertained
by taking a reading of the thermometer hanging in a
convenient place in the room.
The temperature of the water is not quite so readily
obtained. It has been already pointed out that the specific
heat or heat capacity of water is slightly more than
twice that of flour. The temperature of the liquor to be
used may be roughly calculated as follows : Double the
given or fixed temperature for the dough and deduct
that of the flour. Several slight corrections are necessary ;
for example, one for the temperature of the bakery itself,
which ought not to be much lower than 70 F., also
the necessary correction for the effect of the room itself.
BREADMAKING PROCESSES AND BREADS 159
An example will make this calculation clear.
The temperature of the dough is to be 80 F., that
of the flour is 68 F. Find the temperature of the liquor.
Dough temperature=80 ; then 80 X 2= 160.
160 68=92 F., the liquor temperature.
Correction (1).
The bakehouse is very cold, therefore the proper allow-
ance depending on several factors must be added. If
the room is hot, then a deduction should be made.
Correction (2).
The bakehouse is draughty, or the vessels containing
the sponges, doughs, etc., cause a loss of heat, then an
increase must be made to allow for these conditions.
The characteristics of the yeast and its freedom or
otherwise from bacteria, ought to be known to the baker.
Where the characteristics of the yeast are constant, as in
the case of a few of the more important British, a Dutch,
and one or two other Continental yeasts, little or no trouble
is occasioned ; but, on the other hand, where the yeasts
are being repeatedly changed or the yeasts themselves are
not constant in quality, as is frequently the case, trouble is
certain to ensue, unless the baker responsible tests the
various yeasts day by day.
The character and constants of the flour or blends of
flour should also be known. Thus if a flour is excessively
moist owing to the use of an ' atomiser ' or special treatment
in the milling, or if its gluten has been affected or even
degraded, or if it has had the benefit of some artificial
strengthening agent, these facts must be known by the
baker to enable him to obtain the best possible result from
his raw materials.
Strong flours should be employed for long-sponge or long-
fermentation processes, so that the various agents acting
may have time to mellow down and mature the undesirable
constituents in such flours. In this way, spring wheat
flours of the Minnesota Patents type may be rendered
suitable and useful. For doughing up, winter wheat and
softer flours are desirable. For example, a flour milled
160 CHEMISTRY OF BREADMAKING
from soft English wheat imparts a nutty flavour and
improves the colour, bloom, and general appearance of the
finished loaf.
For the short processes, including straight doughs, port
and country millers prepare from a suitably selected grist
the flours required for the trade in their own and other
districts. Flours of this kind are very useful to the baker
and save him from holding large stocks of several varieties
of flour, as was necessary in the days of long processes
when bakers blended to a far greater extent than they do
in modern times. Furthermore, the high quality of the
bread may be more readily maintained.
Having considered the fundamentals, the baker may now
proceed to set his sponge and carry out all the required
operations.
For a long-sponge process, say, for example, one of ten
hours' duration, the following quantities of materials
will be necessary, assuming the bakery plant in this case
to be a two-sack one :
Flour, two sacks or five hundred and sixty pounds.
Yeast, fourteen to sixteen ounces.
Salt, six and a half to seven pounds.
Yeast food, say, malt flour, two pounds.
Water, fifteen to sixteen gallons per sack, as
determined.
The sponge is known as a ' half sponge.' For the setting
of this, use :
Flour, two hundred and twenty to two hundred and
forty pounds.
Yeast, sixteen ounces.
Salt, a pound to one and a half pounds according to
the season.
Water, fifteen gallons.
In many bakeries the sponge is prepared in the old-
fashioned sponging machine, consisting of a tub fitted
with a stirrer or beater. In more modern establishments
a t dough-mixer is used for a similar purpose. It will be
noticed that the ratio of water to flour is roughly one
BREADMAKING PROCESSES AND BREADS 161
gallon to sixteen pounds. This gives a moderately stiff
sponge, therefore if it is to stand for a long period the
temperature must be fairly low, say about 72 F. When
ready, dough up with the remaining materials.
It is important to note that the yeast must be very
thoroughly broken up, or separated cell from cell. In the
case of straight doughs this mixing of the yeast with water
so as to leave no lumps is much more necessary than in
sponging.
The salt should be dissolved completely in some of the
liquor before using, as also should any sugar or malt extract
which is to be used.
The temperature of the water for breaking up yeast must
on no account exceed 104 F., or the fermentative pro-
perties of the yeast may be very seriously impaired. This
and all other operations must be carefully checked or con-
trolled by the use of thermometers. The fingers are not by
any means sensitive enough to be employed as thermometers.
The liquor temperature for doughing depends on a
number of factors, hence no statement of a hard and fast
character can be given.
When once the dough has been made up it should not
be exposed to rough handling, and as fermentation proceeds
this becomes increasingly important. On the other hand,
it should be borne in mind that the texture and other
points of the loaf are brought out and improved by judicious
working. Doughs ought not to be cut back too frequently
as it entails too great a loss of the carbonic acid gas.
For an eight hours' sponge, about a third more yeast
should be employed, at the rate of twelve ounces per sack.
For a good many years bread was prepared for our
military forces by sponge processes and patent hop yeast.
The barm was manufactured from three pounds of ground
malt, which was mixed with soft water into a thin mash
and gently heated to temperatures varying between
145 and 168 F. according to the season. The mash
was then well-stirred together and left to stand for about
one and a half hours. Simultaneously, two ounces of bops
L
162 CHEMISTRY OF BREADMAKING
were infused in four gallons of water and maintained at
200 F. for the same period as the mash. The hop
infusion was then cooled down to 160 F. and strained
into the malt mash, the mixture being well stirred, covered,
and allowed to stand for ten hours. It was now strained
into a clean, well-scalded barm tub, and four ounces of
sugar and half a gallon of yeast from a previous brew
mixed with it. After again stirring, fermentation was
continued for ten hours. The froth and dirty brown
head was skimmed off and the yeast was ready for use.
Three kinds of sponges were used, viz. the quarter, half,
and three-quarters. The quantity of yeast employed
amounted to nearly a gallon per sack of flour. After
dropping twice, salt at the rate of four pounds per sack
and the rest of the water were added and the whole worked
up into a rather stiff dough. For two-pound loaves the
dough was scaled at thirty-five and a half ounces, moulded,
proved, and baked at 550 F. in side-flue ovens.
The straight dough process. 10 The straight dough or
' off-hand ' process is one in which the whole of the in-
gredients are brought together and made into a dough at
one operation.
This involves a number of considerations, some of which
have already been discussed. For example, all types of
flours are not available for use by this method ; thus a
strong, harsh flour would produce large, ungainly loaves
more or less devoid of flavour and of poor colour. If a
weak type of flour is used, then the volume and colour are
poor, but the compensation for these deficiencies is an
excellent flavour in the bread.
To overcome these difficulties the baker had to keep large
stocks of flour for blending purposes in order to obtain the
bread suitable for his trade. Perhaps the greatest difficulty
was with the yeast. Until the days of quick-working,
pressed, distillery yeast, the baker had to rely on barms or
brewers' yeast. When doughs are made up and worked
parallel as far as possible, one with brewers' and the other
BREADMAKING PROCESSES AND BREADS 163
with distillers' yeast, all the advantages, with one exception,
viz. that of risk from sourness, are on the side of the latter.
Owing to the antiseptic properties of the hop constituents
bacteria are very largely held in check, and this obviates
the above risk where brewers' yeasts are employed.
The quantities of materials for an eight-hour straight
dough would approximately be :
Flour, a sack of two hundred and eighty pounds.
Yeast, twelve to fourteen ounces.
Yeast food, eight to ten ounces of a mixture con-
sisting of six parts of good malt flour, four of
sugar, and one of potassium phosphate.
Salt, three and a half pounds.
Water, fourteen to fifteen gallons according to the
strength of the flour, and of such a temperature
that the dough shall be between 73 and 74 F.
As a rule much shorter processes than eight hours are
advisable for straight doughs, viz., from two to three
hours in the dough, or from four to five hours from start
to finish. To carry out the shortest useful process, i.e. four
hours from flour to bread, the following modifications are
necessary :
Yeast, two and a half to three pounds per sack.
Yeast food, one pound of a diastase paste or the
above mixture.
Salt, three pounds.
Water, the same volume at such a temperature that
that of the resulting dough is about 83 F.
The mode of working is somewhat as follows : First
thoroughly break up the yeast in a gallon of water at
90 F., then stir in with it the whole of the yeast food.
Next, pass the flour, after having ascertained its tempera-
ture, through the sifter, so as to open out and get rid of
lumps and foreign particles, into the dough-mixing machine,
and set the arms revolving to lighten and aerate the flour.
While this is proceeding dissolve the salt completely in a
portion of the liquor from the attemperating tank, the
temperature of the water in which lias already been ar-
164
CHEMISTRY OF BREADMAKING
ranged. The required quantity of water is run into the
mixer with the salt and the yeast, which latter should be
in a state of active fermentation or ' krausen ' by this time.
The mixer (Fig. 41) is now closed, and the mixing operation
carried out until the
dough is thoroughly
made and cleared.
The time for this
operation varies
slightly with the
different designs of
machines, but eight
to ten minutes is
long enough in
many cases.
The dough is
turned out into a
Fig. 41. Dough Mixer, showing the in-
terior of the machine.
[By permission of Messrs. Joseph Baker trough, covered up
and Sons, Ltd.}
ment. The temperature of the dough should be taken
as soon as it is collected in the trough and at intervals
during the fermentation. These temperatures ought to be
entered in a book kept for the purpose to enable the foreman
to control all operations properly as in other fermentation
industries. At the right time the dough should be ' cut
back,' brought on to the working tables and thoroughly
kneaded but not too roughly handled. In a quick process
this is most important if the texture, colour, volume, and
flavour are to be at their best. The handling of the dough
during the fermentation stage assists the flavour and
texture especially, by expelling the waste gases and
incorporating fresh air in their place; this revives the
vital activity of the yeast and enables it to complete its
work in the dough constituents. Then if the gases (includ-
ing air) are evenly distributed through the dough, the
reticulation and vesiculation of the crumb of the loaf are
certain to be regular and the texture good. Moreover,
the handling has a toughening effect on the gluten and
BREADMAKING PROCESSES AND BREADS 165
assists its elasticity. Instead of bringing the dough on to
the working tables for the purposes explained above it may
be carried out, though not so effectually, in the dough troughs
by systematically working from one end to the other.
According to Professor Wood of Cambridge, ' the volume
of a loaf depends on the amount of carbonic acid gas
evolved during the fermentation stage, and the power of
the flour to hold the gas ; and a quick evolution distends
the dough much more than a slow evolution.' But, as
already shown, the volume depends on the mechanical
structure, i.e. its vesiculation, as well as on the strength of
the little sacs of gluten which contain the mixture of gases.
For commercial bread, a similar treatment is given to the
dough just before it is ready for scaling ; but for exhibition
loaves an additional handing up will improve all the points
of a loaf previously mentioned. Scaling may best be
carried out by hand, for at this point any rough treatment
of the dough seems to deaden it, or in the words of the
baker ' to knock the life out of it.' Machines known as
dividers have been designed for the purpose, but so far
they are not quite free from this defect. Some are worse
than others in this way, and produce with the same flour
a rather smaller volume loaf.
Great care ought to be exercised before scaling off to
prevent ' over-fermentation,' which is largely the cause of
sourness and crumbliness in the finished loaf. When the
dough is brought into the oven, it takes some time for the
heat to check the yeast action near the centre of the loaf,
hence the necessity of avoiding such a state of things.
Overproof will also help to render bread crumbly.
After scaling, the dough is roughly moulded and placed
close on the tables, to prevent chilling and the streaks it
causes in the bread, and allowed to recover somewhat
before making up. In all the succeeding operations after
fermentation increasing care is required to prevent rough
handling ; very frequently, good loaves are spoiled in
their appearance both externally and internally in this way.
Moulding for different classes of bread is a process that
166 CHEMISTRY OF BREADMAKING
differs considerably and can be better understood by
actually working at the moulding than by any amount of
description.
The moulded dough is now allowed ' to prove ' until it
is at the precise point when baking is required. The
proving apparatus should be of such a form that all draughts
are avoided, so that there is no risk of causing a thick skin
on the surface of the dough which spoils the appearance of
the finished loaf. Where skinning does occur, the surface
of the dough should be lightly washed with warm water
a few minutes before being brought into the oven. This
treatment assists but does not altogether do away with the
disfigurement.
The mode of setting bread in an oven is described in
Chap. XII. on ovens. It is only necessary here to em-
phasise the statement already made that the dough must
not be roughly treated. In setting in, loaves are often
spoiled by throwing them on to the peel or oven-plate at
this stage instead of lightly placing them in position.
The dough should be evenly baked at the temperature
most suitable for the particular class of bread. If the
oven is too slow the dough is dried rather than baked,
and if too hot the crust is over-caramelised before the
interior or crumb is effectually cooked. In both cases
also the volume of the loaf is generally smaller than it
should be. In a slow oven the bread, especially cottage,
is inclined to drop before the heat can fix the gluten,
whereas in the scorching oven the outside crust is fixed
and rendered impervious before the interior gases have
properly expanded. This also very often leads to bursts in
the side and to ugly loaves. Practically, whatever may be
the baking temperature of the ovens, that of the interior
of a loaf only slightly exceeds that of boiling water. The
author in 1905 carried through a large number of experi-
ments on this subject, using specially constructed maximum
thermometers for the purpose. When the dough was being
moulded, the thermometers were placed as near to the
centre of the loaves as possible. Different baking tempera-
BREADMAKING PROCESSES AND BREADS 167
tures were employed, short and long baking periods, and
different classes of breads were subjected to these tests.
After cooling down the loaves containing the instruments
were cut open and the thermometers read, but in no single
case was 216 F. exceeded.
The changes proceeding in the dough during the baking
may be summed up as follows. The surplus moisture is
expelled together with the alcohol and the volatile acidity
(acetic acid) formed at the expense of the alcohol. The
little sacs or cells of gluten and starch gradually expand,
causing the vesiculated appearance of the crumb of the
loaf ; after a time the gluten and certain other nitro-
genous compounds are coagulated ; the moistened starch
of the dough is then gelatinised and becomes fit for food
purposes. The yeast and bacteria are killed by the
moist heat and thus the bread is sterilised. Externally,
the starchy matters become somewhat caramelised, forming
dextrin-like and other more complex carbohydrate com-
pounds, while the traces of acidity convert some of these
bodies into reducing sugars. Wet, naked steam, which is
always present in the ovens both from the cooking dough
and also when introduced either by means of small, narrow
water- tanks, or by wet low-pressure steam, assists the latter
changes, and also forms a larger proportion of dextrins,
thus covering the crust of the loaves with a glaze. Wet
steam in addition tends to counteract the fierce flash-heat
of many of the modern ovens and thus partially preserves
the goods from burning.
As soon as completely baked, the bread is drawn and
stored in bread-racks in a suitable place for cooling down.
The bread at this stage requires careful handling, or the
loaves will be shaken and several of their characteristics
spoiled. After cooling, the bread should be weighed, and
where it is considered advisable, made up in clean paper
wrappers to preserve it from dust and all contact with
dirty or soiled surfaces. A strong pronouncement in
favour of this procedure was made at the Plymouth
Conference in July 1911 by the retiring president of the
168 CHEMISTRY OF BREADMAKING
National Association of Master Bakers. It certainly has
the advantage of keeping the bread from contact with
dirty clothes and hands during the distribution to customers.
As far back as the time of Pliny the Elder it was known
that bread should weigh one-third more than the flour from
which it is produced ; a sack of good- quality flour ought to
yield from three hundred and seventy to three hundred
and eighty-four pounds of bread.
The loss of the dough in baking averages just slightly
more than a tenth of the weight of dough from which the
bread is made, but these figures are frequently exceeded,
greatly to the detriment of both the bread and the baker.
The short, straight dough process for making bread just
described is only possible where high quality yeast and a
regular supply of it can be obtained.
These short processes entail the use of higher tempera-
tures, which tend to cause sourness, i.e. acidity, and poor
flavour ; hence there must be more skill and attention on
the part of the baker, in order to produce a good-coloured
crumb and a fine bloom on the crust.
Colour of the crumb depends on a number of factors,
amongst which are : the quality of the flour, the quantity
of water employed, the method and thoroughness of
working so that everything is kept strictly to its proper
time and place, and the perfection of the aeration. Any
slight deviation from these factors will more or less seriously
affect the colour and other properties of the loaf.
Incidentally, the colour is also influenced by the use of
improvers. For example, fat of various kinds when rubbed
into the flour assists the shortness of the bread, especially
the crust, and improves the flavour and keeping qualities,
but if used in much larger quantities than three pounds per
sack, it not only spoils the colour but makes the dough
' runny.' Other improvers u act somewhat similarly.
The processes and quantities already given are those
employed on a large scale, and with slight modifications are
applicable to all the common classes of bread. For special
breads or the fancy breads of commerce there are nearly as
BREADMAKING PROCESSES AND BREADS 169
many recipes and minor changes as varieties of breads
themselves. Of these, the crusty breads are the more
useful and saleable ; examples, Coburgs, Brunswicks, large
and small Viennas, etc.
Most of these contain fats or milk and sugar or other
improver in addition to the fancy patent flour.
They may best be made by a quick straight dough
process. The following quantities will be found useful
for small batches of any of the above goods :
Flour, fancy patent, or a strong high-class blended with
a proportion of Hungarian flour, sixteen pounds.
Yeast, four to five ounces.
Yeast food, three to four ounces.
Salt, three ounces.
Fats, about three ounces to keep the crust short.
Liquor, seven pints (half milk and half water).
Temperature of the dough to be about 84 or 85 F.
Hand up twice and scale off in two hours. Mould up in
the desired shapes, prove for a time in steam, complete in
the absence of steam. Cut batons, Coburgs and Brunswicks
deeply. Wash with warm water and half bake under
covers to obtain a fine glaze ; take off the covers and
finish. For Vienna smalls, baking trays similar to those
used for petits choux will be found suitable.
For brown breads of all varieties it will be found that
straight dough processes give the best results, and, for
many, the time from flour to finished loaf should not
exceed two and a quarter to two and a half hours. This
does not apply to malt and certain proprietary breads for
which a longer time is necessary owing to the extended
baking period.
The following quantities are suitable for whole and
wheat meals :
Meal, sixteen pounds.
Yeast, six ounces.
Salt, four ounces.
Sugar, two or three ounces.
Water, one gallon, or a portion of this replaced by milk.
170
CHEMISTRY 0$ BREADMAKING
The temperature of the dough to be about 82 to 83 F.
Allow to ferment until ready, then hand up and scale
off at weights to suit the trade of the district, but not
exceeding thirty-five and a half ounces. A two-pounds
brown loaf is the largest size in common use. Set in the
oven slightly underproof. It is important to note that the
temperature of a dough must never be allowed to drop if
good results are to be secured, and this is particularly the
case with all forms of brown breads.
Another note of caution may be useful in making brown
bread. During the making into dough a fine texture may
be secured by rubbing the batter on the table until it has
been fined down, but bread prepared in this way is usually
devoid of flavour and the characteristic colour of the
particular bread.
The chemical composition of bread. The composition
varies somewhat with the process employed in the manu-
facture and with the ingredients used ; thus scalded flour,
potatoes, and such like bodies, yield a moister loaf. The
subjoined analytical figures will enable the reader to gain
some idea of the quantities of the constituents present.
White
Constituents.
White
(tin).
White
(crusty).
White (by
Konig).
(by
Owen
Simmons).
Water
39-64 %
37-24 %
38-5 %
40-0 %
Carbohydrates
52-23,,
52-98
52-1
50-0
.Fibre or Cellulose
0-22
0-23
0-3,,
i-o,,
Proteins
6-77,,
7-95
6-9,,
7-0,,
Fats
0-40,,
0-68
0-8,,
1-0
Mineral Salts
0-60,,
0-73,,
1-2,,
i-o,,
Acidity (Lactic)
0-14,,
0-19,,
0-2,,
The quantities of water in Manchester tin loaves vary
between 33 and 46 per cent., in brown breads (whole and
BREADMAKING PROCESSES AND BREADS 171
wheat meals) between 38 and 45 per cent. The water in the
crust of white bread varies from 17-86 to 26-54 per cent,
with an average of 20-10 per cent., while the crumb contains
from 22-86 to 47-35 per cent, with an average of 42-68 per
cent.
Breadmaking machinery. A well-equipped, up-to-date
machinery bakery ought to contain an installation so
complete as to render it unnecessary to handle the dough
except to set it in the ovens. The important machines
include : A hoist of the vertical or horizontal type fixed in
the highest part of the building, and in such a convenient
position as to be useful for all the required purposes.
An automatic weighing and self-registering machine.
A combined blender and sifter fixed over the hopper of the
dough mixer.
The dough mixer, which should be one of an approved
type, either on the Adair rotary or other principle. In
close proximity to the mixer, a properly constructed
attemperating tank with all the necessary fittings. Dough
and flour troughs and working tables, all of some suit-
able wood free from resins, etc. Kneaders, dividers, and
moulders, the latter adjustable for either tin or cottage
doughs. A dough brake for sundry purposes. A sack-
cleaning machine to recover flour from the sacks ; various
provers, setting and other racks, scales and sundry utensils
as necessary.
Wherever possible the motive power should be electricity
on account of its cleanliness, ease of manipulation, and its
being always ready for use. 12
CHAPTER XI
ANTISEPTICS AND BAKEHOUSE HYGIENE
ANTISEPTICS, as the name denotes, are substances used for
the prevention of putrefaction and decay. In a bakery or
other place in which food is prepared scrupulous cleanliness
must be observed in every possible way. Particles of
sugar, flour, bread, and pieces of dough should never be
allowed to remain on the floor to be trodden about the place,
nor should they be merely swept up to a corner or side of
the room where they act as breeding-places for all kinds of
noxious germs. All tables, troughs, scales, machinery,
and other utensils must be thoroughly cleaned as soon
as possible. Where boiling water can be employed it is
one of the most effective agents in keeping places and
articles both clean and sterile. Soda and soaps are useful
detergents, but they are of little value for sterilising
purposes. Many groups of bacteria are aided by the
presence of very weak solutions of alkalies, hence the use
of one or more of the antiseptics sold for the killing of these
germs and maintaining everything as sterile as possible
is desirable.
The more common antiseptics are : sulphurous acid
gas and its solution, the acid- or bi -sulphites especially
wiose of soda and lime, borax, boric or boracic acid,
salicylic acid, fluorides of the alkalies, lustril, fluosili-
cates, formaline, a 40 per cent, solution of formaldehyde
in methyl alcohol, benzoic acid, and carbolic acid or phenol
when in a strong solution. Phenol, thymol, and certain
other chemical reagents are also classified as antiseptics,
yet their action is somewhat restricted ; for example,
strong solutions of phenol hinder both fermentation and
172
ANTISEPTICS AND HYGIENE 173
putrefaction, but a stiff solution of gelatin containing
phenol is a recognised medium for the culture of certain
groups of bacteria. Again, phenol interferes with and
stops the peptonising action of pepsin, but it apparently
does not influence diastatic action in any way. Thymol,
the chief constituent of oil of thyme, prevents the work
of yeast, moulds, and other ferments, especially diastase,
but it has no effect on pepsin. Use is made of these
different reactions of the two antiseptics in detecting the
one enzyme group in the presence of the other. The three
common fruit acids, viz. malic, tartaric, and citric acids,
and their potassium acid salts, when in weak solution,
prevent all diastatic action, but have no effect on the
alcoholic fermentation, which, it should be remembered, is
known to be caused by enzymes.
The difference in behaviour of antiseptics in some cases
is probably due to the fact that certain of the enzymes have
the protection of a cell-wall as with yeast.
The late Professor Dr. Louis Pasteur based his method
for the preparation of pure yeast on the inhibitive action
of the three acids mentioned, and also on that of phosphoric
acid. Yeasts may be cultivated in the presence of weak
solutions of the four acids, whilst the growth of most
bacterial groups is absolutely prevented by them.
The action of moist heat, that is, boiling water and steam,
has already been discussed.
The bactericidal action of light is of great importance.
Pathogenic and septic or putrefactive bacteria are all
inhibited by the action of plenty of sunlight. As far back
as 1877 a paper of some interest was read before the Royal
Society dealing with the preventive action of light on
bacteria. A few years later Dr. Richardson explained the
bactericidal action of light as a possible case of low tempera-
ture oxidation, because water vapour induces the formation
of hydrogen peroxide which is undoubtedly an antiseptic.
At the Paris Exhibition in 1900 the powerful effect of light
was very forcefully illustrated by cultures of pathogenic
bacteria in glass bottles in gelatin ; portions of the bottles
174 CHEMISTRY OF BREADMAKING
were covered with dark paper, the bottles incubated at
suitable temperatures in bright sunlight and the contents
afterwards completely sterilised. Wherever the dark
paper had prevented light action, dense colonies of bacteria
could be seen, whilst in the exposed parts the nutrient
gelatin remained perfectly clear.
The lesson for the baker is that all parts of the bakery
in which individuals are engaged and food prepared must
be freely exposed to light and fresh air. It is owing to
these two desiderata that the Health Authorities in towns
and urban districts have to a very large extent done away
with the underground and cellar bakehouse. The great
Greek philosopher's statement that ' Light is God's
shadow ' is particularly applicable to any building in
which our daily food is being prepared.
An account of the mode of preparation and properties
of the antiseptics named in this chapter may be found in
any good book on chemistry. As sulphurous acid and its
salts, the bisulphites, are the commonest and most useful of
antiseptics for a bakery, it may not be out of place to state
that these compounds are prepared on a large scale for many
manufacturing processes in the following way. Crude
sulphur or disulphides or other sulphur ores of metals are
roasted and burned in a suitable tray furnace in an excess of
air. The sulphur dioxide (S0 2 ) formed is passed through
purifiers and then into water to be absorbed, or into solu-
tions or milks of the alkalies and earthy metals to form
the bisulphites of them. For example, bisulphite of soda
a liquid is obtained by passing the SO 2 gas into a
moderately strong solution of caustic soda until the soda
is saturated. The bisulphite of lime, the most useful of
these antiseptics, is prepared by treating milk of lime in
a similar way.
All wooden and earthenware vessels that have contained
dough, sugar solutions, yeast, milk, or other substances
which are suitable materials for the growth of moulds and
bacteria, if not already sterile, may quickly be rendered
so by washing with a weak solution of this latter antiseptic,
ANTISEPTICS AND HYGIENE 175
allowing it to remain on the vessel for a short time and then
washing off with boiling water.
In order to assist in keeping everything sterile, the walls
of a bakery ought to be thoroughly cleaned, scraped, and
lime-washed twice a year at convenient periods. Where
possible, white glazed tiles or bricks should be employed
in the construction of the important rooms of the bakery,
because they not only make the place lighter but more
readily lend themselves to cleanliness. Further, glazed
surfaces prevent deposits of dust and bacteria on the walls.
VENTILATION
By ventilating is understood the exposing of something
freely to the action of the atmospheric air ; thus the name
of the process ventilation is derived from the Latin
word ventilo, ' to toss in the air ' (ventus=wmd). The
original idea of ventilation consisted in causing draughts
to exist in all parts of the ventilated structure, thereby
carrying out the exposure to ' little winds ' and in addition
creating much discomfort and even pain to the persons
working in the place.
Natural ventilation depends upon two well-known
phenomena : convection currents, and the diffusion of
gases. All openings into a room or workshop permit of
the entrance of air currents, as also to some extent do the
walls, which are slightly porous. This fresh air mixes
with the air in the rooms by diffusion, and when it becomes
heated it rises to the highest point, thus setting up convec-
tion currents ; the polluted air escapes through any open-
ings it may find, as, for example, by way of the chimney
or the upper part of the door casement, or other opening.
In this way the air of the room is being continuously
changed. The English system of heating by means of
open fires, hence by radiation, though wasteful and extra-
vagant, is healthful, as it is of considerable assistance to
the natural ventilation. That the door is an aid to ventila-
tion may readily be demonstrated by partially opening it
and holding a taper or candle at three different points.
176 CHEMISTRY OF BREADMAKING
At the top the flame from the candle will be blown out-
wards by the outrush of the heated air ; at the bottom
of the door the flame will be blown inwards by the
incoming currents of air. Midway between the top and
bottom of the door there is neither outward nor inward
current. In the winter- time and other cool periods of the
year a sensitive thermometer will also show, by the varia-
tion in temperature, the same effects as does the flame,
namely, that the warm air is rushing out at the top and
the cooler air coming in at the bottom.
When rooms are heated with stoves one or more openings
should be constructed at the upper portion of the rooms so
as to assist in ventilating them ; at the same time stoves are
liable to render the atmosphere of the rooms excessively
dry by raising the temperature too much above the dew-
point, and thus they cause much inconvenience and un-
pleasantness to those inhabiting the rooms. It is advisable
in all such cases to keep a vessel full of water on the stove
in order to prevent this dryness.
Several systems of artificial ventilation are comparatively
common in large buildings in the more important towns.
Up to the present none of these systems are perfect, though
some are more full of imperfections than others. One of
these systems, best known as the ' Plenum System,' passes
the outside air through a kind of purifying and attemperat-
ing plant and then distributes, by means of channels below
thessfloors, warm and cool purified air into rooms at will.
This treated air is not by any means the same as the air
from the outside, as may be perceived by its effect on
different individuals. At the best it is only a system of
dilution, which changes the atmosphere in rooms fairly
quickly without creating too strong draughts, save in the
winter-time when the outside temperature is low; the
draughts from windows and other openings to the outer air
are then apt to be excessive.
The necessity for ventilation. In these days when the
elements of hygiene are taught in every primary school,
ANTISEPTICS AND HYGIENE 177
it is scarcely necessary to discuss this part of the subject.
That ventilation is desirable is sufficiently proved by
comparing vital statistics concerning bakeries of thirty
years ago with those of the present day. Since the Medical
Officers of Health have enforced the observance of more
cleanly habits of working, of better arrangements in
bakeries, of more regular living amongst the working
bakers, and of better means of ventilation, the health,
general conditions of life, and the length of life of the
baker have all enormously improved.
There still remains much to be done to improve further
the health of the worker and consequently to lessen the risks
of disease being spread from this source. In order to keep
in good health at least three thousand feet of air are required
for every adult person even when doing nothing, hence
when at work more than this will be necessary. To obtain
such a quantity, the atmosphere must be frequently
changed in the rooms ; to do this efficiently, the dimensions
of the rooms must be ample, say, not less than six hundred
cubic feet of space per worker, and the ceiling never less
than ten or twelve feet in height from the floor. Added to
this there should be plenty of window space for the admis-
sion of light ; separate rooms for feeding and resting ;
scrupulous cleanliness both in person, clothing, and in the
rooms. Then the life of the worker would be more
wholesome than it is in many cases at present.
CHAPTER XII
FUELS AND OVENS
THE name * fuel ' is given to any material that can be used
to feed a fire so as to generate heat ; fuels therefore may
occur in each of the three states of matter gas, liquid, and
solid. Hydrogen, carbon, carbon monoxide, marsh gas,
ethylene, acetylene, and benzene, when treated or combined
with oxygen, all generate much heat ; when the combustion
takes place with air, the nitrogen present acts as a diluent
and considerably lowers the resultant temperature.
Hydrogen combines with oxygen to form water ; carbon
with oxygen to form, first, carbon monoxide and then carbon
dioxide ; in all these cases much heat is developed that can
be put to practical use. All the other bodies mentioned
contain carbon combined with hydrogen ; the products of
combustion with oxygen will be carbon dioxide and water.
These two compounds are the ultimate products of com-
bustion when hydrocarbons and carbohydrates are burned
in oxygen or air.
It should be the aim in all cases of burning to generate heat,
to burn the common fuels completely to these bodies, and
care must be taken not to use an excessive quantity of air ;
otherwise the air acts as a diluent and causes cooling. All
matter not completely burned before the chimney is reached
means a loss of heat ; hence all carbon in the form of soot,
hydrocarbons, carbon monoxide and other unburnt bodies,
points to considerable waste and loss of heat if allowed to
pass into the outer atmosphere. Chimney gases ought to
consist of nothing but carbon dioxide, water, nitrogen, and
178
FUELS AND OVENS 179
the small excess of air used. Instead of which very large
proportions of carbon and carbon monoxide exist in all
chimney gases, together with the volatile products from the
impurities in the fuel, e.g. sulphur dioxide from sulphur
bodies like brasses, ammonium compounds from the nitro-
gen constituents, etc.
The chief gaseous fuels in common use are : water gas,
ordinary coal gas, carburetted coal gas, oil gas, Mond gas,
regenerator gas, and natural earth gases from the neigh-
bourhood of oil wells. The chief constituents of these
gases are enumerated in the list given above ; in a word,
they contain the three elements, carbon, hydrogen, and
oxygen ; therefore to obtain the maximum heating effect,
all other conditions being equal, nothing but carbon
dioxide and water with the excess air should pass into
the chimney.
Liquid fuels include shale oils, petroleum oils, denatured
alcohol, and some few other liquids. All liquid fuels before
combustion are converted into gases and therefore act
similarly to gaseous fuels. In using the shale and pet-
roleum oils, care must be exercised in keeping the burner
or carburetter clean, or else loss ensues and noxious
vapours will be emitted.
The common fuels are the solid ones, and these include
various classes of coals and cokes, wood, charcoal, and peat.
The particular form of fuel to be used must in a measure
depend on the type of oven, hot plate or other baking
plant. Thus for side-flue, wagon ovens, and similar types
of internally heated ovens, a fuel that gives flame is
necessary ; but with hot-air and steam-pipe ovens coke is
more suitable.
The effectual method of stoking is to keep the bars clean
and free from clinker, and when fuel is required, to push
the red-hot cinders towards the back of the furnace and
spread a thin layer of fresh fuel near the front of the fire.
A kind of distillation of the new fuel then takes place.
in which the gases formed pass over the bright part of the
fire and are burnt, giving rise to a maximum amount of
180
CHEMISTRY OF BREADMAKING
heat with a minimum loss of fuel products. Where large
quantities of fuel are charged into the furnace, there is a
great cooling down of the fire, and production of excess smoke,
loss of time in heating the ovens and considerable waste
of fuel being thereby caused. Clinker may be prevented
from forming on the fire-bars by keeping a jet of steam
or trough of water just below the fire-bars in the ash-pit.
OVENS
Ovens are classified in various ways, either according
to their construction, methods of using, methods of heating,
or the class of goods
to be baked. Thus
there are draw-
plates, peel ovens,
shelf ovens, etc. ; or
they are said to be
either internally or
externally heated
ovens, or hot-air or
steam-pipe ovens,
side-flue ovens,
wagon ovens, Vienna
ovens, and the like.
Shelf ovens (Fig.
42) are generally
small in size, contain-
ing two or more
separate shelves or
baking compart-
ments, and suitable
for a small mixed
trade of bread and
confectionery. All
Fig. 42. A Portway Portable Oven.
[By permission of Messrs. Appleby & Co.]
the chief oven builders supply several sizes of these ovens.
They are all externally heated by coke, coal, or gas.
FUELS AND OVENS 181
All the other varieties resolve themselves into either
internally or externally heated.
The former are the original type, and include the old-
fashioned wood-heated oven which gives so sweet a crust,
and has recently been proclaimed as the only kind of oven
in which ' standard bread ' can be baked ; also the side-
flue, wagon oven, and similar ones. The externally heated
types include hot-air ovens and steam-pipe ovens.
Side-flue ovens are generally single deckers, constructed
of a flat 'sole ' laid with special one-foot square tiles, upright
sides, and a crowned arch at the top. At one side is built a
short furnace which leads abruptly into the oven round
which the flames and heated gases pass on their way out
by the flue at the top near the mouth of the oven. Dampers
are necessary in order to control the furnace.
The wagon oven is an older style than this, for it consists
of the oven without the side furnace. An iron box wider
at the upper parts of the sides than at the bottom is the
wagon. This is piled up with fuel, lighted and brought
into the centre of the oven as far back as possible. An
iron pipe of suitable dimensions traversing the whole length
of the oven is fixed into the wagon at the one end and
passes through the door into the outer air, thus supplying
the necessary oxygen for the combustion. The outlet flue
is at the top near the mouth of the oven. When not in use,
as during the baking period, this opening is closed by a
damper.
In both cases the ovens are ready for use, or are said to
have become solid, when all the carbonaceous matter has
been burnt off and the walls glow with heat. Both these
ovens are also designated peel ovens, since they are filled
and drawn by means of a long-handled wooden spade
known as a ' peel.' In the case of the side-flue special
precautions are necessary in setting in and drawing.
The loaves slightly underproof are set in on the coolest
side of the oven ; if cottage loaves, just touching one
another and equidistant. The loaves at proof or slightly
over are set on the furnace side, but protected from the
182 CHEMISTRY OF BREADMAKING
fierce heat on this side by setters or dummies and a long,
narrow, open vessel full of water. The wet steam generated
tempers down the fierce heat, prevents burning and glazes
the bread by forming dextrins, sugars, and caramel-like
bodies. The last loaves to be set in a side-flue oven are
usually the first to be drawn. The chief disadvantages of
these ovens are that they are wasteful of fuel, dirty, and not
continuous. The advantage is that the heat is solid, and
they give a sweet- eating crust. Where they are used in a
Fig. 43. A Range of five single Draw-plate Steam-pipe Ovens.
[By permission of Messrs. Joseph Baker and Sons, Ltd.]
mixed trade, the bread is baked first, then smalls, and after-
wards the confectionery goods.
Externally heated ovens are heated either by means of
hot-air currents circulating over and around the oven (or
ovens, as these are often constructed in pairs, one placed
above the other), or by being built inside an enclosed
heated space, or by steam-pipes. Steam-pipe ovens have
become very common in recent years on account of the
advantages they possess over the other types (Fig. 43).
These are as follows ; They are cleaner, cheaper to work, as
FUELS AND OVENS 183
they take less fuel, are healthier, speedier, and continuous
in their action. The important disadvantages may be
summed up as follows : They give a flash heat, are some-
what dangerous owing to the liability of the pipes to burst,
are more costly to erect in the first case and difficult to
regulate properly.
They may be built as double drawplates or a drawplate
with a peel oven over the top. This latter arrangement is
especially suitable for a mixed trade and where confectionery
goods form a part of the business. Within the last three
years, drawplate ovens with half-inch thick tiles have been
devised so as to render the drawplate suitable for the
baking of buns and other smalls. The furnace in steam-
pipe ovens is small in size arid may be arranged on one side
or at the back of the block. The bottom layer of pipes
which heat the bottom part of the lower oven forms the fire-
bars in the furnace. The second row of pipes heats the upper
part of this oven, and in many cases is immediately below
the tiled sole of the top oven, the ends of these pipes coming
into the furnace. The top row of pipes is in the upper
portion of the baking space of this top oven, with the ends
bent downwards so as to come into contact with the heat
from the furnace. There are also sundry flues for heating
purposes, such as sets of coils to provide boiling water for
use in the bakery, dry provers, etc. ; these flues all connect
with the main flue which passes into the chimney. The
pipes vary in length according to their size and their
position in the oven. Their external diameter is usually
one and five-sixteenths of an inch, and their internal
diameter about five- eighths of an inch, thus forming a
fairly thick- walled tube. The tube holds about three-
quarters of a pint of well-boiled water, and it is said to be
tested up to a pressure of three thousand pounds per square
inch of surface before being sent out of the factory. Such a
statement can scarcely be verified after a pipe is welded
and sealed. In these ovens heat is conveyed and dispersed
by the three processes-r-conduction, convection, and
radiation.
184
CHEMISTRY OF BREADMAKING
The sizes of ovens. Ovens vary in size from a half to
two sacks capacity, that is, they are capable of holding the
bread made from those quantities of flour. A half-sack
oven should possess a baking chamber of 30 to 33 square
feet, say 6 feet long by 5 feet in width ; a three-quarter
sack about 8 feet by 6 feet, or 48 square feet ; a sack size
60 to 63 square feet ; a sack and three-quarters, 1 1 feet by
9 feet, or 99 square feet ; a two-sack about 12 feet by 10
feet, or 120 square feet. The usual allowance is two square
feet of oven space for three cottage loaves, or a little less
r?-.^^\\L!MEWNCREJE^7,
^Q&i :.<. :.\'-~^-y ''..:, ? '' '
'<ING
.PACE *
STOKING}
FLOOR
"&'*-+,-:**'."
SliliSlSllfe^
4-4. fit.pfl.Tn-nmft OVATV
Fig. 44. Steam-pipe Oven.
[By permission of Messrs. Joseph Baker and Sons, Ltd.~\
for tin bread. Thus an oven 11 feet by 9 feet should hold
about 140 cottage loaves scaled at 71 ounces for quartern
size, or 150 tin loaves scaled at 71 J ounces in the dough for
four pounds or quartern size.
Vienna ovens. These are constructed with a sole slop-
ing from the back to the mouth (Fig. 45), the sole at the
back being slightly higher than the upper part of the
mouth of the oven, so that steam may always be kept in
the oven during the baking of Vienna goods, as this keeps
them crisp and soft and at the same time glazes them.
FUELS AND OVENS
185
Vienna ovens are heated either by side-flue or steam-
pipes. The author has invariably found the best work,
, - -v ^ - - ;>,^J|fep^|^|pf^
Fig. 45. Baker's Patent Vienna Oven. Section showing a single
oven fired at the back. (Note the sloping sole.)
\By permission of Messrs. Joseph Baker and Sons, Ltd. ]
as regards the baking, turned out by the side-flue heated
Vienna ovens.
The following table gives approximately the temperatures
and pressures in steam-pipe ovens :
Pressure
in Ibs.
125 .
150 .
Pressure
in Ibs.
15 .
20 .
25 .
30 .
40 .
50 .
100 .
Temp, of
Oven.
250
259
267
274
292
301
338
F.
165
230
235
415
420
Temp, of
Oven.
.353 F.
. 366
.373
.391
.400
.447
.450 ,
CHAPTER XIII
THE ANALYSIS OF CEREAL FOODS
Water testing. For the purposes of breadmaking a water
should be free from floating particles and not too hard,
whilst it must be organically pure.
The physical tests may be readily carried out as follows.
Obtain a fair sample of the water by allowing the tap to
run for a minute or two, or if from a well by first pumping
a few strokes to clear the pipe and then collecting the
sample for the tests.
To test for colour bring some of the water into a tall, colour-
less glass cylinder or test glass, and place the vessel on a
sheet of white paper in a position away from sunlight. If
possible fill a similar vessel with pure distilled water and
compare the two samples. Distilled water is devoid of
colour, taste, and smell ; the nearer the water sample comes
to this, the better. Very often a strongly contaminated
water possesses a pleasant saline taste.
After carrying out the above test bring pieces of red and
blue litmus paper into the sample, allow to stand a few
minutes, then note any change that may have taken place.
Pure drinking water should produce no change in the
litmus papers.
Too large a quantity of solids in solution may be detected
by boiling down given volumes of the sample and of a
known pure water on a water bath in any suitable vessel
and comparing the quantities of solid matters left behind.
Distilled water leaves no residue. In most cases, where
there are large quantities of solids in solution, the waters
will be hard or require a considerable quantity of soap to
form a lather.
WATER TESTING 187
The hardness may be roughly tested by dissolving a
small quantity of soap cut into thin shavings in a mixture
of alcohol (spirits of wine) and water. A 4-oz. bottle,
preferably with a glass stopper, is required. Into this
measure out say two ounces of water, either a soft tap
water like that of Liverpool, Glasgow, Manchester, or rain-
water, and add small quantities of the soap solution, shak-
ing very thoroughly after each addition. Note the quantity
of soap solution taken to make a lather that will last four or
five minutes. Clean out the bottle and repeat the operation
with the sample of water to be tested. Note the quantity
of the soap solution required in this case. If only a small
quantity then the water is a soft one, if much it is a hard
sample. If very hard it ought to be softened, by stirring
in the suitable softening agent and allowing to settle, before
being used for bakehouse operations.
Organic impurities of an ammoniacal character may
be tested for by adding a few drops of Nessler's reagent
(which may be purchased from a chemist) to some
of the sample contained in the glass vessel used for
noting the colour. If sewage be present the Nessler im-
parts to the water a reddish-brown shade of colour or even
produces a brown precipitate therein, according to the
quantity of impurity present. Nessler's should not give
more than a faint yellow colour to a drinkable water.
Other organic impurities may be detected by the aid of a
solution of permanganate of potassium used in the acid
condition. About half an ounce of the salt is dissolved in
a quart of well-boiled cold water. A pint of the water to
be tested is brought into a glass flask and a small volume
of weak sulphuric acid added. The pink-coloured perman-
ganate solution is added drop by drop with shaking until
the colour of the contents of the flask remains permanently
pink. The quantity used is noted. If much of the
permanganate solution is required, the water is too con-
taminated for drinking purposes.
The only poisonous metals likely to be present are salts
of lead and iron.
188
CHEMISTRY OF BREADMAKING
The lead may be tested for by the addition of a fevy
drops of sulphuric acid solution when on standing a white
precipitate is formed ; also by adding some yellow chromate
of potash solution, when if lead is present a yellow precipi-
tate settles out. Iron compounds may be detected by the
addition of some ferrocyanide of potash, which causes a
blue coloration or precipitate if much iron is in the water ;
or by adding a solution of tannin, which gives a light pre-
cipitate gradually becoming darker until at last ink is
formed. Tannic acid in contact with iron salts forms
tannate of iron or ink.
NOTE. Quantities of lead and iron salts present in any
water are usually so small that it is advisable always to
evaporate the water to about a quarter of its bulk before
carrying out these tests.
GENERAL METHODS or ESTIMATING THE CHEMICAL CON-
STITUENTS OF THE CEREALS AND OTHER FOOD-STUFFS
Moisture estimation. The processes for this estimation
vary somewhat according to the nature of the substance
in which the estimation is required. Some bodies if
heated above the boiling point of water
212 F. (100 C.) begin to decompose, or
they may suffer oxidation and thus in-
crease in weight. This will give a low
result for the moisture.
Generally, the estimation may be carried
out as follows : A wide, squat weighing-
glass (Fig. 46) is accurately weighed with
the lid tilted on one side so as to admit
air * From five to ten rams of the
substance roughly powdered or cut into
thin shavings is introduced into the glass and weighed.
The glass is then brought into either a water oven
if the temperature must not exceed that of boiling water,
or into an air bath with the temperature maintained
between 212 to 218 F. (100 to 103 C.) for three
THE ANALYSIS OF CEREAL FOODS 189
to four hours with the lid of the glass off. Then desiccate
and weigh. Repeat the heating, cooling, and weighing
until constant. From the loss calculate the percentage
of moisture. Note that, in weighing, the dried substance
the lid of the glass must be on, since dried food-stuffs as a
rule are very hygroscopic. Where other methods are
necessary, they will be given in the proper place.
The estimation of the ash or mineral matter in food-
stuffs. A small platinum dish or capsule, or even a fused
silica dish, is accurately weighed. Five to ten grams of
the roughly powdered food-stuff, such as bread or flour, is
brought into the dish and the whole weighed. The dish
is now brought on to a clay triangle over a bunsen burner,
and the contents gently ignited until reduced to the black
or carbon state. The dish is brought into a muffle furnace
and the carbon completely burned off at the lowest possible
temperature. The dish then contains only a small quantity
of a white to greyish-coloured ash. It is cooled in a
desiccator and weighed. After the first weighing it is
again ignited, desiccated and reweighed, and the operations
are repeated until the weight is constant.
The weight of the empty dish is then deducted from
the final weight and the percentage of ash calculated.
Great care is necessary to keep the temperature down
as low as possible or chlorides may be volatilised. If a
muffle furnace cannot be used, the whole operation must be
carried out with a bunsen or other suitable burner, taking
every precaution in order to prevent loss by volatilisation.
NOTE. The burning off of the carbon in a platinum
capsule over a bunsen burner is materially assisted by
bringing a piece of fine platinum gauze over the capsule.
The action of this is probably of a catalytic nature.
Estimation of silica. This is best obtained from the ash
after burning off the carbonaceous and other volatile
substances.
The ash, which is already in a tared platinum capsule,
is accurately weighed ; cover this with concentrated
190 CHEMISTRY OF BREADMAKING
hydrochloric acid (HC1) and digest on a water-bath for
some time. Then boil to dryness ; again moisten with
dilute HC1 and evaporate to dryness. Take up with hot
water, filter through a Swedish filter paper, wash thoroughly
with boiling water, dry, ignite, desiccate, and weigh.
Repeat the igniting, etc., until the weight is constant ;
then calculate the percentage of silica as Si0 2 , usually on
the weight of the ash.
The phosphates. A fresh portion of ash is to be weighed
out ; digest this with moderately strong nitric acid, boil to
dryness on a water-bath, take up with dilute nitric acid
(HNO 3 ), filter off the silica and wash thoroughly. The
filtrate and washings contain the whole of the phosphates.
Evaporate to about fifty c.c., add a few drops of strong
HNO 3 and about 20 to 30 c.c. of ammonium molybdate
solution. Cover and place the beaker with its contents
in a cool place for twelve hours. The phosphate will be
precipitated as the yellow phospho-ammonio molybdate.
Filter and wash with dilute HNO 3 . Dissolve the yellow
precipitate with warm ammonia, allowing to run into a
clean beaker. Also dissolve the last traces of the yellow
compound with ammonia, wash everything with a small
quantity of fresh ammonia and then add magnesium
mixture to this ammoniacal solution. Cover and again
allow to stand in a cool place for twelve hours.
Filter through a special or Swedish filter paper, wash
with dilute ammonia, dry, ignite, gently at first, then more
strongly, desiccate and weigh. Repeat till constant in
weight. From the amount of pyrophosphate of magnesium,
Mg 2 P 2 O 7 , calculate the phosphate to the anhydride, P 2 O 5 ,
and express as a percentage on the weight of the ash.
The fats. Fats in food-stuffs exist either as glycerides,
or as phosphorised fats, generally glycero-phosphates or
lecithines. - These latter bodies occur in the germ or nucleus
of plants and in the yolk in animal life.
The dry ether extraction process is probably the most
accurate method of estimation. 'In the case of liquids
THE ANALYSIS OF CEREAL FOODS
191
the sp. gr. must be ascertained, then a known volume
5 or 10 c.c. is used for spotting the inside of a Schleicher
Fig. 47. Soxhlet Fat Extractor as arranged for work.
and Schiill fat-free extraction thimble ; this is air-dried
and brought into a Soxhlet extraction apparatus in which
192 CHEMISTRY OF BREADMAKING
the fat is extracted by repeated washings with dry ether
(Fig. 47).
The ether is distilled off and the residue brought into a
small weighed beaker together with the ether washings of
the flask. The ether is allowed to evaporate by placing
the beaker on to the top of an air-bath, the last traces being
expelled by an air blast, then desiccated and weighed.
To extract the fat from solids, a given weight five or
ten or more grams of the dry solid are brought into the
fat-free thimble and treated as described above. With
finely divided substances like flour it is better to use a
double thimble of large size.
Quite recently a new nomenclature of fatty compounds
has been adopted. Those fats containing nitrogen and
phosphorus are termed phospholipines, while those con-
taining nitrogen without phosphorus are named lipines.
The nitrogenous bodies. These are of two classes, those
soluble in water and those insoluble. A known weight of
the solid is brought into a flask of large size and shaken for
some time with a known volume of cold water. The water
is allowed to remain in contact with the solid for one to three
hours. The liquid is then filtered till quite bright and a
given volume evaporated to dryness in a weighed porcelain
dish, desiccated and weighed. From these figures the soluble
extract may be calculated.
For the estimation of the soluble nitrogenous matter the
residue is now treated with 10 c.c. of Kjeldahl acid (Kjeldahl
acid is made up of equal volumes of concentrated and
twenty-five per cent, fuming sulphuric acids), transferred
to the small long-necked hard glass flask, one to two grams
of mercury oxide added together with a piece of white
paraffin wax about the size of a pea to stop frothing, and
heated strongly till the whole of the residue is dissolved and
the contents of the flask are quite clear but not necessarily
colourless. The clear liquid is diluted with water and
transferred to the distilling flask of an ammonia apparatus,
the small flask carefully washed out and the washings
THE ANALYSIS OF CEREAL FOODS 193
added to the contents of the distilling flask. The apparatus
is next connected together, caustic soda solution run into
the acid liquid and the ammonia distilled over into a known
volume of standard acid ; the excess acidity is then titrated
with standard alkali and the ammonia calculated to
nitrogen. N X 6*3 proteins.
Where the estimation is to be carried out with solids,
the weighed quantity of dried solid is introduced into the
hard glass flask together with either mercury oxide or
fused bisulphate of potash or phosphoric anhydride
(P 2 5 ) and the 10 c.c. of Kjeldahl acid. The process is
then as already described. This latter determination
gives the total quantity of nitrogenous matter in the
substance, while the former gives the soluble or that which
is already available for food purposes. The quantities
taken for estimation vary from 5 to 10 c.c. of the soluble
extract, and from one to ten grams of dry solid according
to the quantity of nitrogenous matter present. Thus with
a wholemeal much less would be required than with either
white flour or bread.
THE EXAMINATION OF WHEAT AND OTHER CEREALS
A general external examination of the wheat berry
should be made by the aid of low powers on a compound
microscope. For the purpose it is better to get a complete
spikelet with the husk, glumes, and berries intact ; then the
microscopic hairs, dust, beard, and other parts may be
seen. Sections, both transverse and longitudinal, should
be cut, examined, stained, and again examined. The
germ ought also to be excised and examined, and the hollow
from which it was removed carefully observed.
For the purpose of cutting sections the grain must be
soaked in water at about blood-heat (98*4 F.) for twenty-
four or thirty hours according to its condition. The
sections are cut by means of a very keen razor. As soon as
cut, they must be brought on to a micro-slip, a drop or two ot
water added, covered with a glass, and examined forthwith.
The starch may be stained blue with very dilute iodine
N
194 CHEMISTRY OF BREADMAKING
solution, the excess of iodine washed, off with a spray of
water, and the nitrogenous bodies (gluten) stained pink with
haematoxylin solution. The pericarp and testa, which
together form the bran, and the aleurone cells may easily
be seen without staining. Similar sections of the little
germ may also be cut and examined. Other cereals should
be treated in like manner, and the points of similarity to
and difference from wheat noted.
THE CHEMICAL ANALYSIS OF THE CONSTITUENTS
or CEREALS
This consists in the estimation of moisture, ash, fat,
starch, cellulose, reducing and other sugars, dextrins,
total nitrogenous matter and soluble extract, including that
of the soluble nitrogenous content. The acidity of the
soluble extract may also be determined.
For the estimation of the moisture, ash, fats, and nitro-
genous matter, whole grain may be used, but it is advisable
in every case to employ meal obtained by grinding up the
berries in a small mill. The general processes already given
are quite suitable for these determinations.
The soluble extract. The soluble extract refers to
substances soluble in water, such as gums, sugars, dextrins,
certain nitrogenous compounds, and mineral salts. Ten
grams of the finely divided substance are accurately weighed,
placed in a flask, and covered with 200 c.c. of pure distilled
water ; a cork is inserted to close the flask, and the contents
are repeatedly shaken at intervals during the time the
mixture is allowed to stand. One hour has been found by
experiment to be too short, therefore it is advisable to
permit the extraction to go on for three hours. During the
last half-hour refrain from disturbing the contents of the
flask. Then filter till bright. Withdraw an aliquot
proportion, say 50 c.c., and evaporate to dryness on a
water-bath in a weighed porcelain or silica dish. Dry off in
a water oven for fifteen minutes, desiccate and weigh.
After the weight is constant, the contents of the dish are
THE ANALYSIS OF CEREAL FOODS 195
ignited, first over a bunsen burner till carbonised and then
finished off in a muffle furnace. Desiccate and weigh.
The result gives the amount of mineral salts extracted
by cold water.
The calculations are simple. Ten grams in 200 c.c.
give a five per cent, solution and mixture. Fifty c.c.
are taken for evaporation, or a quarter of the whole ;
50 c.c. therefore contain the amount of soluble matter
from two and a half grams of the original material. By
deducting the weight of the dish the amount of soluble
matter in the two and a half grams is obtained. Multiply
this weight by four and then by ten to give the percentage
of soluble extract in the grain, flour, or bread. The weight
of the ash is also multiplied by .forty to give the percentage
of mineral salts extracted.
An example will make this clear.
Weight of silica dish and dry extract =73-066 grams.
Weight of silica dish =72- 952
Weight of dry extract = 0-114
Therefore 0-114x4x10=4-56 per cent, of extract.
The acidity determination. The acidity of cereals and
cereal products is due partly to the acid phosphates
present and partly to organic acids. Whatever may be
the cause of it, the acidity is always calculated as
lactic acid, C 3 H 6 O 3 , or CH 3 -CHOH.COOH (molecular
weight, 90).
The acidity may be quantitatively estimated in an
aliquot portion of the soluble extract. The liquid, as in
the previous estimation, must be filtered bright, then
25 c.c. are withdrawn by a pipette, brought into a small
flask, a few drops of an indicator such as methyl orange
added, and then titrated by means of a burette with centi-
normal alkali, preferably caustic soda. A second portion of
25 c.c. is similarly titrated, and the mean of the two results
used to calculate the acidity*
196 CHEMISTRY OF BREADMAKING
Example of an acidity calculation :
Twenty-five c.c. of a XX flour soluble extract required
/ N \
(1) 2-6 c.c. and (2) 24 c.c. of centinormal ( J caustic
\1UU/
soda. Mean 2-5 c.c.
N
One c.c. of caustic soda contains 0-0004 gram of
100
soda, therefore 2-5 c.c. contains 0-001 gram.
Now 40 parts of caustic soda =90 parts of lactic acid.
Therefore 0-001 of caustic soda= Q ' QQ1X9Q
40
=0-00225 lactic acid.
25 c.c. of soluble extract contain 0-00225 lactic.
, T , , 0-00225 X 100
100 c.c. of soluble extract contain =0-009
lactic.
100 c.c. are the extract from five grams of flour and con-
tain 0-009 lactic. Therefore 100 grams of flour contain
0-009x100 A10
=0-18 per cent, lactic.
Reducing and other sugars and the dextrins. A further
portion of the clear, bright soluble extract is employed for
the sugars and the dextrins. This consists in determining
(a) the opticity of the liquid ; (b) the copper-reducing power,
and calculating this to maltose ; (c) treating with dilute
acid for twenty-five minutes to hydrolyse sucrose to invert
sugars and again determining the copper-reducing power.
(a) The specific rotatory power (S.R.P.) or opticity.
The S.R.P. of any optically active substance is the angle
through which a beam of plane polarised light of definite
degree of refrangibility is rotated on passing through a
layer of the substance a thousand millimetres in thickness
and containing ten grams of substance per hundred c.c.
of the solution. Or, it may be defined as the amount of
turning that a beam of polarised light undergoes when it
passes through a metre length of a ten per cent, solution of
the substance.
THE ANALYSIS OF CEREAL FOODS 197
In practice it is very difficult to pass a beam through
a column of liquid one metre long ; therefore it is usual to
employ tubes of one or two decimetres in length, and
to multiply the reading by ten or five as the case may be.
At the same time the errors are increased in the same
proportion.
The two instruments in common use for the determination
of the opticity of sugars and other optically active carbo-
hydrates are the Laurent, which is used with a sodium flame,
and in which percentages of cane sugar (sucrose) may be
read off directly ; and the Schmidt-Haensch, a white light
instrument, the readings of which may be converted into
angular measure by multiplying by 0-344.
To use the Laurent polarimeter : First adjust the zero
point of the instrument and note any correction. Note the
temperature of the room in which the instrument is placed ;
the readings are accurate between 60 and 68 F. Rinse
out the previously cleaned tube with a few drops of the
liquid to be determined ; fill the tube completely, slide on
the top glass disc and affix the end. Bring into position
and take the reading at once. Also take a reading with a
second tube ; the two readings should coincide. The
calculation may be simplified by using the formula :
S.R.P., (a) D -IQOXtt
3-86 Ixc
where a=the angle of rotation.
1= length of tube in decimetres.
c= concentration or grams of solids per 100 c.c.
Example. Find the percentage of cane sugar in the
sample in which the length of tube used was two decimetres,
the solids 9*86, and the angular rotation 12-85.
Then == =66-162 S R P
IXC 2X9-86 19-72
The S.R.P. of 100 per cent, sucrose is 66-5.
Therefore in the example, 65 ' 162XlQQ =98-73 per cent.
66'5
of sucrose.
198
CHEMISTRY OF BREADMAKING
To convert yellow light (a) D readings into white light
(a)j readings, multiply by 1-1084, the product
(a) D X l-1084=(a) j .
Example. The S.R.P. of sucrose (a) D is 66-5. Find the
S.R.P. for white light (a) r
66-5x1-1084=73-70.
The following figures represent the accepted S.R.P. for
the pure substances :
Substance.
S.R.P. for (a) D .
S.R.P. for (a)..
Dextrins
200-4
216-0
Maltose
138-0
150-0
Sucrose
66-5
73-8
Dextrose
52-8
58-52
Lsevulose
95-65
105-98
Invert sugar
21-3
23-60
Lactose
52-53
57-22
Raffinose
104-5
115-83
Frequently, solutions which are to be examined by
polarised light, although quite bright, are so darkly
coloured as to prevent a beam of light passing. In such
cases it is advisable to use a decolorising material. The
three common ones are alumina cream, basic lead acetate,
and bleaching powder solution. In every case the
minimum quantity of these solutions should be employed,
as they carry down sugar and introduce other errors.
For 100 c.c. of a ten per cent, solution of sugar, from 2J
to 5 c.c. is usually sufficient. Bring 50 c.c. of the sugar
solution into 100 c.c. flask, add 2J or more c.c. of alumina
cream or other reagent, make up to the hundred mark
with pure distilled water, put in the stopper, shake up,
allow to settle for a few minutes, filter and take the neces-
sary readings. Should the alumina cream not be efficient
try the basic lead acetate, or both together, using the lead
first. Not more than 5 c.c. of the two combined may be
THE ANALYSIS OF CEREAL FOODS 199
employed. Very occasionally, in ordinary practice, the
bleaching powder method of decolorisation may be re-
quired, or even the boiling up with finely ground animal
charcoal.
NOTE. 1 on a Laurent instrument represents 0-1619
grams of sugar (sucrose) per hundred cubic centimetres of
solution.
(b) The copper-reducing power of sugars. All the more
common sugars, except the sucroses, possess the power of
reducing, in a greater or less degree, an alkaline copper
tartrate solution, commonly known as Fehling's solution,
to the state of red cuprous oxide, Cu 2 0. K, the copper-
reducing power of a sugar, is defined to be the amount of
cupric oxide, CuO, calculated to dextrose that a hundred
parts will reduce. As dextrose possesses the highest
reducing power, it is taken as the standard for comparison.
The values for K are as follows :
For dextrose=100 ; for maltose=61-07.
For lsevulose=92-4 ; for invert sugar=96-6.
Fehling's solution is made up as two solutions, which are
not mixed until required for use.
(1) Dissolve 69-2 grams of pure recrystallised copper
sulphate CuS0 4 -5 H 2 O, in water and make up to a litre.
(2) Dissolve 346 grams of Rochelle salt and 130 grams
of caustic soda (both these compounds must be pure) in
water and make up to a litre. If flocculent matter settles
out, the solution must be filtered through glass wool.
When required, 25 c.c. of each solution are mixed together
to form 50 c.c. of the clear, dark blue liquid known as
Fehling's alkaline copper tartrate solution. One molecule
of pure dextrose is able to reduce exactly five molecules of
this copper solution ; or, 0*05 gram of pure dextrose
exactly reduces 10 c.c. of standard Fehling's solution. 14
To use Fehling's reagent, bring 50 c.c. of the Fehling
into a white glazed porcelain beaker, add 40 c.c. of distilled
water, place in a water-bath and bring to the boil. Then
into this, by means of a pipette, run 10 c.c. of the reducing
sugar solution, cover the beaker with a clock glass and
200 CHEMISTRY OF BREADMAKING
boil exactly twelve minutes. Take out of the water-bath,
allow to settle for a few minutes, and filter off the red
cuprous oxide through a Swedish filter paper. Wash out
the beaker very thoroughly, wash all the blue copper salt
out of the filter paper, dry, ignite, desiccate, and weigh as
black oxide of copper, CuO. During ignition the carbon
of the filter paper reduces some of the oxide of copper to
the metallic state. Dissolve this with about two drops
of strong nitric acid, and again ignite to convert the copper
nitrate into CuO.
= CuO + 2N0 2 + 0.
N0 3
Copper nitrate = Copper oxide + Dioxide of nitrogen + Oxygen.
Weight of CuOxO-7435=maltose.
NOTE. It should be arranged that the 10 c.c. of reducing
sugar solution contains between 0*10 and 0*15 grams of
sugar.
By the process described, the reducing sugars, if any, in
the cold water extract of cereals may be accurately deter-
mined. If sucroses are present these must be hydrolysed
to invert sugar. Ten c.c. of the extract are brought into a
small glass flask, 1 c.c. of HC1 added and the liquid heated
in a water-bath for twenty-five minutes at boiling point.
The acid is neutralised with about 1 c.c. of caustic soda
(NaOH) solution, and the copper-reducing power deter-
mined as already explained. Deduct the CuO, if any, from
the reducing sugars, from the total CuO obtained in this
determination and calculate the remainder to sucrose.
Weight of CuOxO'4715x^J=cane sugar or sucrose.
The dextrins present can be determined directly by the
process given, or as is usually the case indirectly from the
total S.R.P. The sugars found by the copper-reducing
process are calculated to their opticity (S.R.P.). This is
deducted from the total S.R.P., and the remaining S.R.P.
calculated to dextrins.
The dextrins, which do not reduce Fehling's solution or
Knapp's mercuric cyanide solution, may be freed from
THE ANALYSIS OF CEREAL FOODS 201
dextrose and maltose by heating with an excess of an
alkaline solution of mercuric cyanide which oxidises the
two sugars without affecting the dextrins present.
Five grams of the substance containing the dextrins
are dissolved in water, the solution made up to 100 c.c. at
60 F. and filtered bright if necessary ; 10 c.c. of this are
boiled with 10 c.c. of Knapp's reagent, filtered bright, and
the S.R.P. of the solution read off in a Laurent polarimeter
as already described, and the percentage of dextrins
calculated. Where the mercury is found to interfere, it
may be precipitated with sulphuretted hydrogen gas and
the liquid filtered bright before the opticity is taken.
Estimation of starch in cereals. The starch in cereals
is usually determined by a modification of the original
method devised by Maercker.
Finely crush about four grams of the wheat or other
cereal, then weigh accurately three grams into a glass
bottle, cover with distilled water and heat in a pressure
vessel for about an hour. Cool to 150 F. Stir in 5 c.c.
of malt extract, the value of which is known, and maintain
at 145 or 146 F. for twenty-five minutes. Make faintly
acid with tartaric acid solution, then again heat under
pressure. Cool as before, treat with another 5 c.c. of malt
extract for thirty minutes, then bring to the boil for five
minutes. Cool to 60 F. and make up to 100 c.c. in a
graduated flask. Filter till bright. Determine the copper-
reducing power with 10 c.c. Also take the rotation or
opticity. From the figures obtained, calculate the per-
centage of starch.
The estimation of starch in flour, commercial starch, etc.
This determination is based on that of Dragendorff. The
starchy matter is generally mixed up with fats, proteins,
sugars, colouring matter, amylans, pectins, mineral salts,
etc. Three grams of the finely ground substance are
mixed in a flask with 30 c.c. of a five per cent, solution of
caustic potash, heated for twenty-four hours on a water-
202 CHEMISTRY OF BREADMAKING
bath, filtered while hot through a weighed Swedish filter
paper, and the residue on the filter paper washed with hot
absolute alcohol, cold ordinary alcohol, and lastly with
water; then dried at 230 F. (110 C.), desiccated and
weighed.
The loss is that of the foreign substances mentioned
above. The amount of the remainder, minus the weight of
the filter paper, agrees approximately with that of the
starch and fibre (a). The filter paper and its contents are
then cut up, placed in a flask, boiled with distilled water for
an hour, cooled to 150 F., treated with 5 c.c. of malt
extract of known value, maintained at 146 F. for thirty
minutes, brought up to the boil for five minutes, filtered
hot through another weighed filter paper, washed, dried,
desiccated and weighed (6). The difference between the
weights of (a) and (b) gives the starch. The fibre or cellulose
is the residue minus the weight of the two filter papers.
The starch may also be determined by cooling the
contents of the flask after boiling to 60 F., and determin-
ing the copper-reducing power in 10 c.c. and also the
opticity.
Estimation of the fibre or husky matter, or cellulose.
Weigh out approximately two and a half grams of the
substance, grind, then weigh accurately two grams into a
small flask. Add enough of a one per cent, solution of
sulphuric acid to more than cover the material and boil
for at least half an hour. Pour off as much of the acid as
possible, replace with a one per cent, solution of caustic
potash and again boil for half an hour. Exhaust very
thoroughly with the reagents in the order given cold
water, concentrated alcohol and ether ; then dry and
weigh. Even after the above treatment the cellulose
contains traces of wood-gums, suberin and its acid,
silica, hydro-cellulose, etc.
According to Professor A. G. Green, this fibre cellulose is
a colloidal aggregate of a large number of somewhat simple
cellulose molecules.
THE ANALYSIS OF CEREAL FOODS 203
FLOUR ANALYSIS
As a preliminary to the chemical analysis, all flours
should be subjected to a physical examination. This
includes the handling to observe the condition, i.e. whether
granular and free or soft and woolly. If pressed tightly
in the hand high-grade flours fly off in all directions, or
appear to squirt from between the fingers. Inferior ones
ball and clog, especially if unduly moist. Any unpleasant
odour, or anything unusual in general appearance, should
also be noted.
The colour of a flour is determined by the Pekar test,
first in the dry, then in the wet and afterwards in the dried
state. A known high-grade flour ^>f the pale, creamy,
bloomy appearance should be used as a standard for
comparison.
The strength of flour is an unsettled factor, dependent
largely on the quality and condition of the gluten. It can
only be considered in connection with the absorbing power,
the retaining power, the gluten, and the viscosity of such
flour.
The gluten may be approximately determined as follows :
Weigh out accurately twenty-five grams of the flour into
a glazed porcelain dish, size IV. or V. Make it into a clear
dough with 12 or 13 c.c. of cold water. Cover the little
ball of dough with cold water, and allow to stand for
between thirty and sixty minutes.
Wash out the starch and soluble matters in a large
excess of water, being careful not to separate the dough.
Pour off the water into another dish, and note that there
should be no gluten particles or pieces of dough at the
bottom of the vessel. When the washings no longer
become milky and the gluten contains no lumps of visible
flour and is practically of one shade of colour, the excess
water may be pressed out, the gluten brought on to a piece
of counterpoised aluminium foil (thin sheet aluminium)
and weighed in the wet state, and its percentage calculated
204 CHEMISTRY OF BREADMAKING
by multiplying by four ; this result divided by three gives
approximately the percentage of dry gluten. The wet
gluten may then be dried in an air-bath at 212 to 218 F.
until the weight is constant. The figures obtained will
agree very closely with those from the calculated dry-
gluten. Two estimations should be carried out, and the
condition, colour, and other points noted before the gluten
is dried ; the mean of the results is taken as the percentage.
The separation of the gluten into glutenin and gliadin
is effected by washing out the gluten in the ordinary way,
weighing to obtain - the wet gluten ; then this and the
aluminium foil are brought into a flask containing about
100 c.c. of strong alcohol, digested on a water-bath for some
time, and filtered. The residue is washed with strong
alcohol, dried and weighed to give the insoluble glutenin.
The alcoholic filtrate is distilled to recover most of the
alcohol, the rest containing the sticky gliadin is transferred
to a small weighed beaker, the alcohol evaporated off, and
the residue cooled and weighed ; the later operations are
repeated until the weight is constant. From the figures
obtained the weight of the gliadin is calculated.
The absorbing power is determined by weighing out
twenty-eight grams of the flour into a glazed porcelain dish
and running measured volumes of water into it from a
burette, then making up into a dough of the proper
consistency. The number of c.c. and decimals of a c.c.
gives gallons and decimals of a gallon per sack of flour
(280 Ibs.). This result can now be confirmed by making
up a batch or dough with seven to fourteen pounds of flour
and proper quantities of yeast, salt, and water, such that
the consistency is the same as before. Weigh the dough
as soon as properly cleared, making allowance for the yeast
and salt. The figures should agree with the result obtained
in the first part of the work.
The dough is then worked through into bread as usual.
Immediately on drawing, the bread is weighed and the loss
calculated. From this the retaining power of the flour is
THE ANALYSIS OF CEREAL FOODS 205
known. According to the condition and quality of the
gluten, whether or not an excess quantity of water has been
put into the dough, whether a sharp or slow oven has been
used, according to the condition and state of the dough, etc.,
the figures obtained regarding the retaining power of the
flour will be affected.
The viscosity time of a dough is also useful in assisting
the worker to understand the quality of a gluten, but so
many factors interfere as to render the results of two or
more workers absolutely useless for comparison. Owing
to this, it is not proposed to occupy space in describing
the instruments or their manipulation, especially at this
transition stage of our knowledge.
Foreign substances, as starches, crystals of mineral salts,
particles of offal or husky matter, may best be detected by
the aid of a compound microscope.
Bring a small quantity of the dry flour on to a micro-slip
and examine it with low powers, say an ocular number two
and an objective C. or a third of an inch. Make several
dry slides and examine them. Offal, crystals, and other
foreign particles may readily be observed. Next, make
two or three wet slides by stirring a very small quantity of
flour in water, bring one drop on to a slide, place over it a
thin cover-glass and again examine, using an E. or one-sixth
objective. This examination will reveal foreign starches
if any, husky matter, germ and other insoluble bodies.
The chemical analysis of flour. This consists in making
the following determinations : Water, ash, fats, total
proteins, soluble extract including the sugars, acidity,
mineral salts and soluble nitrogenous bodies contained
therein, starch and fibre or cellulose. In addition the
tests for alum and bleaching should be carried out.
The whole of the foregoing - determinations may be
carried out by the processes already given in the description
of the chemical analysis of cereals and their meals.
An example of the determination of the soluble extract,
and the ash of this, in a first patent flour follows.
206 CHEMISTRY OF BREADMAKING
Twenty-five grams of flour were brought into a flask
and treated as already described with 500 c.c. of water.
A portion was filtered bright and 50 c.c. evaporated to
dryness on a water-bath, dried, desiccated, and weighed.
Grams.
Weight of platinum dish and the dried extract =51 -8 154
Weight of platinum dish alone . . . =51-6320
Weight of soluble extract from 50 c.c.= 0-1834
Now 50 c.c. is one-tenth of the 500 c.c., and therefore
contains the extract in 2-5 grains of flour, and this yields
0-1834 grams of extract.
. ,, 0-1834x100
/. 100 grams yield - -_ = 7-34 per cent, of sol-
Z'O
uble extract.
The contents of the platinum dish were then incinerated,
desiccated, and weighed.
Grams.
Weight of platinum dish and the ash =51-6418
Weight of the platinum dish alone =51-6320
0-0098
.-. 100 grams yield ' 09 o 8 r Xl00 = 0-392 per cent, of ash
2*o
in the soluble extract.
Alum may be detected in the following way : Five
grams of the flour are brought into a small porcelain dish,
10 c.c. of a ten per cent, solution of ammonium carbonate
are added and the mixture stirred to form a paste ; then
10 c.c. of a fresh solution of logwood extract are stirred
in, the dish covered, and the whole allowed to stand for a
few minutes. If alum has been used to lighten up and
strengthen the flour, or if a bread improver containing the
constituents of alum has been employed or added to the
flour, a lilac coloration is formed all over the paste. If no
alum is present, a pink to rose colour appears. In all cases
THE ANALYSIS OF CEREAL FOODS 207
%
a control test should be carried out with a flour already
known to be pure.
The logwood extract is prepared by shaking up a small
quantity of fluorescent logwood chips with a comparatively
large quantity of methylated spirit.
The tests for bleaching. These tests depend upon the
presence of nitrites or nitrous acid in the flour, formed by
the action of the oxides of nitrogen from the bleaching
process. The tests generally adopted are those of Dr. Griess,
carried out as follows after the preparation of a soluble
extract of the flour.
(1) Bring some of the clear extract into a Nessler glass
or other similar vessel ; add about six drops of concen-
trated sulphuric acid and a few c.c. of a weak meta-
phenylenediamine solution. Cover the vessel and allow
to stand about fifteen minutes when the Bismarck brown
coloration is formed if any nitrites are present.
(2) Bring some of the clear soluble extract into a Nessler
glass, add one drop of concentrated hydrochloric acid,
one c.c. of sulphanihc acid solution and one c.c. of alpha-
naphthylamine hydrochloride solution, stir with a clean
glass rod, cover and allow to stand for from twenty to
thirty minutes. If nitrites are present, a faint to bright
pink coloration is developed.
NOTE. The water used for making the soluble extract
must be previously tested for nitrites in order to prevent
the possibility of error from this cause.
THE EXAMINATION OF BREAD
Before undertaking an analysis of the chemical con-
stituents of bread, a general examination of the bread, both
externally and internally, should be made as if judging for
exhibition purposes.
Externally, the following points may be considered :
The general appearance of the loaf or loaves, whether
properly handled, moulded, and baked, the bloom if any,
the colour, and the volume.
208 CHEMISTRY OF BREADMAKING
For the internal examination the loaf should be evenly
and cleanly cut through the middle beginning at the top.
The colour, flavour, texture, pile, and regularity of the
crumb should then be examined. Occasionally, it is
advisable to cut a very thin slice from off one of the sections
and hold it up before the strong light from a window not
' facing the sun. This gives an opportunity of more critically
judging the crumb and noting any irregularities. Streaks,
due to the chilling of the dough during the making up, may
thus be more readily traced and other faults distinguished.
The chemical analysis of bread. The crumb or inside and
the crust or external coating of the bread should be ex-
amined separately where necessary. For general analysis
a slice is cut right through the bread and a fair sample
containing the proper proportions of crumb and crust
taken. The following determinations are made : Moisture,
fats, mineral salts, proteins, starch, cellulose, the soluble
extract and in this the sugars, nitrogenous matter, acidity,
alum, and total phosphates, by the processes already given.
If it is necessary to test for bleaching, a thin slice of bread
may be cut, a strong soluble extract made with tap-water,
the liquid filtered and tested for nitrites by the methods
given under flour analysis.
THE ANALYSIS OF THE GERM or CEREALS
The germ or embryo of cereals is a somewhat triangular-
looking body of a yellowish buttery appearance when
picked out from new grain. If the cereal is old, however,
the germ has darkened almost to a deep brown in colour,
and the taste instead of being pleasant is decidedly the
reverse. Wheat germs obtained from the mill are pale
stone-colour to yellowish discs varying from three-sixteenths
to a quarter of an inch in diameter. In a fit condition for
food the germ must possess a pleasant oily smell and an
agreeable greasy flavour. Germ in a decomposed state is
dangerous to health, if used for foods, owing to the products
of bacterial decomposition.
THE ANALYSIS OF CEBEAL FOODS 209
The chemical analysis. This consists in the estimation of
the amounts of moisture, fats, ash, proteins, fibre or cellu-
lose, sugars, soluble extract and the soluble nitrogenous
matter, and the detection of enzymes. The whole of the
above bodies may be estimated by the methods already
given under the heading ' Estimation of the chemical
constituents of the cereals,' see page 194.
The detection of enzymes. The enzymes likely to be
present are diastase, cytase, certain proteolytic ones, and
those which emulsify and act on the fats. Diastase may
be detected by bringing a small quantity of the cold water
extract of the germ into a two per cent, solution of soluble
starch, heating up to 145 F. and allowing to act for
half an hour, then boiling and testing for maltose with
Fehling's solution, when the characteristic red precipitate
of cuprous oxide, Cu 2 0, will be obtained if diastatic action
has taken place.
Two examples of the complete analysis of wheat germs
are given below :
Moisture
Fat .
Ash .
Insoluble nitrogenous matter
Soluble extract
Cellulose and fibre .
Starch and undetermined
Soluble extract
Cane sugar .
Maltose
Soluble nitrogenous matter .
Ash ....
Dextrins, gums, and undetermined
Diastatic power (Lintner)
Sample I.
11-55%
8-42,,
4-44,,
18-42,,
40-20,,
2-35,,
14-62,,
Sample II.
13-70%
10-30,,
4-49,,
16-87,,
37-85
3-87,,
12-92,,
100-00 100-00
18-87%
0-12,,
13-26,,
2-88,,
5-07,,
18-64%
0-04,,
12-00,,
2-76,,
4-41
210 CHEMISTRY OF BREADMAKJLNG
THE ANALYSIS OF MALT FLOUB AND EXTRACTS
These should possess the usual appearance, odour, and
taste of such bodies. There must be no traces of fermenta-
tion evident in the fluid products, whilst the flour must be
in a fine state of division and free from lumps, mouldy
smell, and insects. The chemical analysis includes the
determination of the moisture, acidity, ash, sugars, pro-
teins, and the diastatic capacity.
These may be carried out by the usual methods, care
being taken with the moisture estimation not to allow the
temperature to rise above 212 F. It is safer to carry
out this determination in a water oven and so to avoid any
chance of oxidation. This precaution of course applies
only to the solid products, since the moisture in malt ex-
tracts is determined by a method described later.
The determination of the diastatic capacity (Lintner
value). Twenty-five grams of ground malt are extracted
for three hours with half a litre of distilled water at 70 F.,
stirring well every half-hour and filtering bright. Three c.c.
of this bright filtrate are allowed to act on 100 c.c. of a
two per cent, soluble starch solution at 70 F. for one
hour in a 200 c.c. flask. Ten c.c. of deci-normal solution of
caustic soda are then added in order to check diastatic
action, the liquid cooled to 60 F. and made up to 200 c.c.
with distilled water ; the contents of the flask are then well
shaken and titrated against 5 c.c. portions of standard
Fehling's solution, using ferrous thiocyanate as indicator.
This titration is carried out as follows : Five c.c. of
Fehling's solution are accurately measured into a 150 c.c.
boiling flask, and raised to boiling over a small naked
bunsen flame. The converted starch solution is added
from a burette in small quantities, the mixture being kept
rotated and boiled after each addition until reduction of
the copper solution is complete, which is ascertained by
rapidly withdrawing a drop of the liquid with a glass rod,
and bringing it at once into contact with a drop of the
indicator on a porcelain spot plate, the end point being
THE ANALYSIS OF CEREAL FOODS 211
arrived at when no reddish-brown coloration is
obtained.
The indicator is made up as follows : Dissolve one gram
each of ferrous ammonium sulphate and ammonium sulpho-
cyanide in 10 c.c. of water at 120 F. Cool and add 5
c.c. of hydrochloric acid solution. Remove any traces of a
red coloration with a small quantity of zinc dust.
The results are calculated by the help of the following
formula :
A _ 1000
xy
where A the diastatic capacity.
#=the number of c.c. of five per cent, malt extract
contained in 100 c.c. of the fully diluted
starch liquid.
2/=the number of c.c. of the same liquid required
for the reduction of 5 c.c. of Fehling's
solution.
Precautions :
(1) Where a malt has a diastatic capacity of over fifty
degrees Lintner, then only 2 c.c. of the cold water malt
extract is used for the determination.
(2) In the case of a malt extract, use 3 c.c. of a four per
cent, solution of the malt extract in cold water.
(3) With a diastase paste where the Lintner value is
over 60 D.C., then 3 c.c. of a two per cent, solution of the
diastase paste in cold water may be employed.
(4) The value of x in case (2) is arrived at as follows :
3x4
3 c.c. of 4 per cent. solution = =2*4 c.c. of a 5 per cent.
5
solution in 200 c.c. of the liquid, i.e. 1-2 c.c. in 100 c.c.
Example. With two malt extracts (3 c.c. of 4 per cent,
solution used).
(a) In the first case, 5 c.c. of Fehling required 19 c.c. of
the starch.
1000
Then A= =43-86, or 44 Lintner.
L' Zi x ly
(6) In the second case, 5 c.c. of Fehling required 17-5 c.c.
212 CHEMISTRY OF BREADMAKING
1 (\f\f\
Then A=- UUU =47-6, or 48 Lintner.
1*2 X 17*5
A malt or other substance possessing diastatic power
is said to be 100 Lintner, when 0-1 c.c. of the five per cent.
cold-water extract filtered bright, after being allowed to
act on a two per cent, solution of soluble starch for one hour
at 70 F., produces enough malt sugar to exactly reduce
5 c.c. of standard Fehling's solution.
The determinations of moisture and total solids in fluid
malt products, sugars, starch transformation substances, etc.
Ten grams of the substance are accurately weighed out,
dissolved in pure water and made up to the mark in 100
c.c. graduated flask at the temperature of 60 F. The
contents of the flask are thoroughly shaken, and the specific
gravity (sp. gr.) determined as follows :
Thoroughly clean and weigh a 50 c.c. sp. gr. bottle,
then fill with water at 60 F., dry and weigh. Turn out the
water, rinse out twice with the liquid the gravity of which
is required, fill completely as before, clean and weigh.
From the figures obtained, the sp. gr. may be calculated as
under :
Weight of bottle and substance weight of bottle.
^' ' Weight of bottle and water weight of bottle.
Example. A very stiff syrup gives the following figures:
Wfoght of empty bottle . =27-7905 grams.
Weight of bottle and substance= 79-3559 grams.
Weight of bottle and water =77-7556 grams.
Find the sp. gr., the total solids, and the moisture.
g = 79-3559 27-790551-5654
' gr * ~~
= 1-03203 taking water as 1-000,
but with water as 1000 the sp. gr. = 1032-03 for a 10%
solution.
The total solids are found by deducting a thousand from
the sp. gr. and dividing the difference by 3-86.
Therefore
1032-031000 32-03_
3-86 =T86=
THE ANALYSIS OF CEREAL FOODS 213
The total solids in ten grams equal 8-298 or 82-98 per cent.
This deducted from a hundred gives the moisture.
10082-98=17-02 per cent, of water.
NOTE. The factor 3-86, or the solids factor, has been
arrived at by dissolving one gram of the pure substance in
water, making up to 100 c.c. and determining the sp. gr.
which in the case of sucrose works out to 1003-859 ; for
malt products to 1004. For uniformity's sake the factor
3-86 has been adopted for all these bodies and mixtures of
them. Too much care cannot be paid to working out all
sp. gr. determinations at the temperature of 60 F., at which
the apparatus is accurate.
The three required results then are :
Specific gravity, 1032-03 (water=1000).
Total solids, . 82-98 per cent.
Moisture, . 17-02 per cent.
The analysis of sugars. The colour, taste, smell, and
general appearance of the sugar should first be noticed ;
then the chemical reaction towards litmus paper, and the
tests for the presence of iron salts carried out.
High-class sugars when dissolved in water should not
change blue litmus paper to red, nor give the following
reactions for iron salts :
(1) Bring some of the solution into a test tube, add a few
drops of weak nitric acid and some ferrocyanide of
potassium. A greenish-blue coloration and precipitate
indicates iron salts.
(2) To a second portion of the solution add a few drops
of weak nitric acid and some sulphocyanide of potassium.
A pale pink to blood-red coloration indicates iron salts.
(3) To a third portion of the sugar solution add a few
drops of a tannic acid solution. A light-coloured precipi-
tate gradually darkening to black indicates iron salts.
Low-grade sugars are often whitened in appearance by
the addition of a blue ultramarine. The presence of this
body may be detected by making a strong solution of the
sugar and allowing it to settle in a cool place, when a faint
214 CHEMISTRY OF BREADMAKING
blue sediment settles out. A further test may be made by
adding a few drops of weak acid solution to some of the
solid sugar in a test tube and noting the unpleasant smell
of sulphuretted hydrogen. The presence of this is confirmed
by bringing a filter paper moistened with silver nitrate
solution over the mouth of the tube, when a darkening to
an almost black colour indicates the presence of sulphides
which are constituents of ultramarine. Lead acetate solu-
tion (sugar of lead) may be used in the place of silver nitrate.
The chemical estimations of sugar include the following
determinations : The moisture and total solids, by the sp.
gr. method as already described, the mineral salts, total
sugar, other sugars, nitrogenous bodies, the copper-reduc-
ing power, and the opticity, together with the acidity and
iron if these substances have been detected in the pre-
liminary examination. The whole of the above determina-
tions to decide the purity of a sugar may be carried out
by the methods already given.
The following factors may be of use in sugar analysis :
CuO X 0-7435 = maltose.
CuO X 0-4535 ^dextrose.
CuO X 0-4715 = invert sugar.
CuO X 0-47 15 X | = sucrose.
The analysis of milks. The following varieties of milk
are used in the making of bread : Whole milk, skim or
separated milk, and dried milk or milk powders. Whole
milk is an almost perfect or complete food, since it contains
all four proximate principles of food sugars, fats, proteids,
and mineral salts with water.
All milk of cows, when allowed to stand, rapidly increases
in acidity owing to the conversion of milk-sugar into lactic
acid, except when kept at temperatures below 50 F., or
when a powerful antiseptic like formalin, salicylic acid, or
boric acid has been added.
The colour of milk is somewhat variable. This is due
to the fat globules and pigments present. The presence of
chromogenic bacteria readily effects changes in the colour ;
THE ANALYSIS OF CEREAL FOODS 215
thus it may be shades of blue, yellow, or even faintly red.
Such organisms are generally the cause of diseases in milks.
Milk analysis consists in the determinations of the
specific gravity, water, total solids, and fats.
The sp. gr. may be found by the process already given,
or roughly by means of a hydrometer. The sp. gr. varies
between 1027 and 1035 (water =1000). According to
Professor H. Droop Richmond, the average of over six
hundred thousand samples is 1032-1 at 60 F.
The water and total solids may be determined by
bringing 5 or 10 c.c. into a tared platinum capsule together
with a small weighed glass rod to stir the contents ; a
few drops of acetic acid, which is volatile, are added to
coagulate the proteids and so prevent the formation of a
scum on the surface which delays evaporation. The
contents are evaporated to dryness on a water-bath, dried
in a water-oven for a short time, desiccated and weighed.
The loss is that of the water which has been driven off,
whilst the total solids are the residue in the capsule ; these
are calculated to a percentage.
The fats are estimated by the ether extraction process,
or by one of the many centrifugal methods. The analytical
results are generally stated as, total solids, water, fats, and
solids not fat. Analyses of English standard milk and
others are given in the subjoined table :
Constituents.
English
Standard.
An Ordinary
Sample
(local).
A Low-
grade
Sample.
Dried
Milk
(whole).
Water,
Total Solids,
87-50 %
12.50
86-84 /
13-16
95-63 %
4-37
8-96%
91-04
Fats, .
Solids not Fats,
Mineral Salts,
Proteids,
Lactose,
3-50
9-00
0-72
3-53
4-75
4-04
9-12
0-73
3-57
4-82
1-27
3-10
0-34
1-03
1-73
15-56
75-48
5-73
27-15
42-60
Sp. Gr. at 60 F.,
1032-0
1032-2
1010-2
216 CHEMISTRY OF BREADMAKING
Dried milks may be analysed by the processes already
given. The proteids are determined by the Kjeldahl
method (NX 6- 3= proteids). The lactose in all the above
cases is estimated by difference.
BIBLIOGRAPHY
Atwater, Mrs. H. W., .
Bayliss, Dr. W. M.,
Blandy, John,
Fowler, Dr. G. J. }
Goodfellow, Dr. John, .
Hansen, Dr. E. C.
Harden, Dr. Arthur,
Hutchison, Dr.,
Jago, William,
Jago, William,
Jorgensen, A.,
Kirkland, Archibald,
Kirkland, John, .
Kirkland, John, and
others,
Klocker, Dr. A., .
Lafar, Professor Franz, . .
Lawes and Gilbert,
Maercker, Dr.,
Matthews, Charles G., t
Newlands, B. E. K.,
Osborne, Dr. Thomas B.,
Osborne, Chittenden, and
others,
Scott, Charles and James,
Sherman, H. C., .
Simmons, Owen, .
Snyder, Dr. Henry,
Snyder, Dr. Henry,
Bread and the Principles of Bread-
making.
The Nature of Enzyme Action.
Studies in Breadmaking.
Bacteriological and Enzyme Chemis-
try.
The Dietetic Value of Bread.
Practical Studies in Fermentation,
and Pamphlets.
Alcoholic Fermentation.
The Dietetic Value of Foods.
The Principles of Breadmaking.
The Technology of Breadmaking, etc.
The Micro-organisms of Fermenta-
tion.
Studies for the Bakehouse.
AIL about Breadmaking.
The Modern Baker, Confectioner, and
Caterer.
Fermentation Organisms.
Technical Mycology. Vols. I. and II.
The Wheat Grain, its Milling Pro-
ducts and Bread.
Die Kohlenhydrate.
Manual of Alcoholic Fermentation.
Sugar.
The Vegetable Proteins.
The Proteids of Wheat, etc.
Vienna Bread.
The Carbohydrates of Wheat.
The Book of Bread.
Studies on Bread and Breadmaking.
Digestibility and Nutritive Value of
Bread.
217
218 CHEMISTRY OF BREADMAKING
Stone, W. K, . . The Carbohydrates of Wheat, other
Cereals, and Bread.
Tollens, Dr. B., . . Handbuch der Kohlenhydrate.
Tucker, J. H., . . Manual of Sugar Chemistry.
Wanklyn, Professor J. A., Bread Analysis.
Wells, Robert, . . Bread, Biscuits, Buns, and Cakes.
Wiley, Dr. H. W., . Cereals and Cereal Products.
Woods and Merrill, . Digestibility and Nutritive Value of
Bread.
Encyclopaedias. Britanmca, Chambers, Harmsworth, and
Ure.
Science Progress. Ethics of Food: Bread, April 1911;
Wheat, October 1910.
Also the many trade journals published regularly.
ADDENDA
1. AMMONIA (Page 12). There is more of this gas in the
atmosphere at night than in the daytime, owing to the
decomposition of nitrogenous organic matter. In a thousand
parts of air London contains 0'05, Glasgow 0'06, and Man-
chester O'lO of ammonia gas.
2. HUMIDITY (Page 13), or to deal with it quantitatively,
HYGROMETRY. This is the condition of any atmosphere as
regards aqueous vapour, (a) the amount of vapour present,
(b) the ratio of this which would saturate the air at the actual
temperature.
To hygrometry our sensations of dryness and moistness
chiefly depend. In the bakery, a knowledge of this subject
is important, in order to enable us to prevent the ' skinning '
of any doughs exposed to the air, and thus prevent the
spoiling of the bread both externally and internally.
3. HEAT (Page 42). The effect of heat on matter is to
expand it in the three dimensions of space, length, depth,
and width, or, as it is generally known, the cubical expansion
of matter.
Cooling, on the other, hand, causes matter to contract in
all its dimensions.
4. LENS (Page 47). The constants of a lens are its axis,
focal length, and optical centre.
In the diagram :
POP' is the principal axis ;
LP and L'P' are each the
focal length ; P and P' are
the principal foci; and
is the optical centre of the
lens.
5. ALCOHOL (Page 59). Additional facts concerning spirits
219
220 CHEMISTRY OF BREADMAKING
of wine. . It boils at 78 C., has a Sp. Gr. of 0-793 at 15 C.,
and of 0-806 at C.
Proof Spirit at 51 Fah. weighs y of an equal volume of
distilled water, and contains 49 '26 parts of ale. by weight or
57-09 per cent, of ale. by vol. Thus, 100 galls, of 25 O.P.=
125 galls, of Proof Spirit, while 100 galls, of 25 U.P. = 75
galls, of Proof Spirit.
Methylated spirit is composed of 90 vols. of raw grain
spirit, 10 vols. of wood spirit or methyl ale., and about |
per cent, of sulphur paraffin oil or naphtha.
All the forms of ale. are valuable solvents, whilst spirits of
wine are used for the preparation of many flavouring essences.
6. AMINO- ACIDS (Page 89). It is stated that gluten is a
mixture of compounds glutenin and gliadin each of which
contains an amino-acid. This latter is the name given to a
group of bodies in which the amide NH 2 is directly
attached to a carbon atom. Ex. glycine or amino-acetic acid,
NH 2 CH a COOH. A set of reactions, brought about by
the action of phosphorus pentachloride, PC1 5 , and known as
Fischer's reactions, ultimately result in the formation of
brownish-looking bodies resembling the peptones derived from
egg albumen, hence the name polypeptides applied to them.
When gluten, that has been washed out from flour, is
treated with water free from mineral salts, or with weak
acids, or alkalies, it is broken up, loses its tenacity, and is
partially dissolved.
It has been shown by K. Hoagland that when gluten is
shaken up for about 90 minutes with alcohol of 50 per cent,
strength, at a temperature of about 25 C., the gliadin is
dissolved out, and may be estimated quantitatively. He
states that hard spring wheat flours contain from 7*0 to 10*0
per cent., and soft winter wheat flours about 6-5 to 7'0 per
cent. Working by Hoagland's method, the author finds that
ordinary bread flours contain from 5*68 to 8 '3 7 per cent, of
gliadin in their gluten.
7. 'THE PROPERTIES OF FLOURS' (Page 112). The con-
ADDENDA 221
stants of a wheat flour are the moisture, ash, colour, acidity,
purity, strength, water absorbing and retaining power. This
latter property is dependent on the gluten, starch, and water ;
whilst the strength is a measure of the capacity of flour to
produce a bold, large-volumed, well-risen loaf ; thus strength
regulates the quantity of bread that can be obtained from a
flour.
Many substances have been and are still added to flours to
increase the strength. One of the newest is persulphate of
potassium, KS0 4 . This reagent or percarbonates may be
detected in a flour as follows :
Make ten grams of flour into a paste with water and spray
over it a few drops of a two per cent, solution of Benzidene
in alcohol.
After standing for a few minutes, blue specks or a blue
coloration indicate the presence of persulphates or per-
carbonates.
8. DIASTATIC ACTION (Page 121). It should be noted
that all flours contain some broken starch granules, owing to
the action of the machinery, and on the contents of these the
diastase can act and so produce malt sugar.
9. BRITISH DISTILLERIES (Page 143). The author is glad
to find that the paragraph has had the effect of putting
British yeast producers on their mettle, and thus influenced
the trade for good. On the other hand, it should be stated
that British distilleries are under great disabilities owing to
stringent and awkward excise regulations, which prevent all
hope of competing successfully with continental firms. If at
the present time the yeast firms combined in a petition to
Government some good might result, as in the case of the
coal-tar dyes manufacturers a few years ago.
10. STRAIGHT DOUGH AND OTHER PROCESSES (Page 162).
For students' work in the bakery the exercises in testing
flours are based on the following : For tin bread one Ib. of
flour absorbs about ten ounces of water ; for crusty and
crumby breads about nine ounces ; and for cottage bread
222 CHEMISTRY OF BREADMAKING
about eight ounces. These work out to 17'5 galls, of water,
15'75 galls, and 14-0 galls, of water per sack respectively.
Generally seven Ibs. of the flour, two ounces of yeast, one
ounce of fat or milk powder, and one or one and a quarter
ounces of salt are employed. The yield per sack and other
factors can readily be calculated from the results.
11. IMPROVERS (Page 168). A loaf may be improved and
cheapened by the use of rice. About three to five Ibs. of rice
may be steeped in water and allowed to remain at a boiling
temperature until quite gelatinised, then put through a sieve
as with potatoes, and added to a sack batch. The doughs
should be rather stiffer than when rice is not used.
12. GLUTEN BREAD (Page 171). The following process,
one advocated by John Kirkland, gives good results :
( The simplest method of producing gluten bread for your
purpose is to make say one Ib. of strong flour into dough with
half an ounce of yeast, half a pint of water, or a little more
say half an ounce of butter. Keep this in a warm place
to ferment for about three-quarters of an hour, then wash
the gluten from this dough first in about two quarts of water,
then in a second two quarts, then in a third. When you have
finished you will have a tough mass of gluten weighing about
two and a half ounces. Break this into two pieces and roll
sausage shape. Slightly grease a clean baking sheet and place
these two pieces sufficiently far apart and cover each with a
tin perforated with one hole in the bottom. Allow to stand
about ten minutes before baking. Bake in a rather cold
oven one about 360 will serve for one hour. The covers
must not be removed nor the baking sheet touched until the
pieces are quite baked, or they will collapse. The perforation
in the cover is also essential or same thing will happen. When
the pieces are baked they should be very light and pale
in colour and, of course, much larger than when set in
oven. When cold cut into slices about half an inch thick
and sprinkle with fine salt, then re-dry like rusks till crisp
and nicely browned. The water used for washing the gluten
ADDENDA 223
should be kept and used as part of the liquor for making
ordinary dough. For your purpose it is better to make a
small quantity often rather than to attempt a large lot at
once. The best time to bake the rolls would be after the
day's work is done and the oven somewhat cool.'
13. EEDUCING SUGARS (Page 196). For the quantitative
estimation of a reducing sugar in a nearly pure sample of
a sucrose, ex. a 99'8 per cent, caster sugar, it is better to
heat with Fehling's solution at 62 C. for ten minutes rather
Fig. 48. Automatic Travelling Oven.
[By permission of Messrs. Joseph Baker <k Sons, Ltd."}
than at 100 C. as is usual. The quantity of reducing sugar
rarely exceeds O'Ol per cent.
14. To STANDARDISE FEHLING'S SOLUTION (Page 199).
Dissolve 0-5 gram of pure anhydrous dextrose in 100 c.c. of
water. Ten c.c. of this should exactly reduce 10 c.c. of
Fehling diluted with 40 c.c. of water. Titrate in the boiling
state.
15. AUTOMATIC TRAVELLING OVENS FOR CONTINUOUS
BAKING. One of the latest devices for the quick and effec-
224 CHEMISTRY OF BREADMAKING
tive baking of doughs is the endless belt system, in which
the loaves are placed on a conveyor hearth that travels
slowly arid continuously through a hot, steam-tight air
chamber. The loaves are fed on to the plates of the belt at
one end of the oven and delivered completely and perfectly
baked at the opposite end.
Uniformity of colour and evenness of baking are obtained,
since each loaf is in the baking chamber under similar con-
ditions and for the same length of time.
In size these ovens vary from forty to a hundred and
twenty feet in length, and from six to ten feet in width, with
a capacity of 720 to 3000 two pounds loaves per hour.
The driving mechanism of the belt is simple ; inspection
doors are placed at suitable intervals ; a minimum amount of
fuel is required ; there is less wear and tear of tins and pans ;
while the finished bread is of regular appearance, similar in
flavour, and contains a rather larger amount of moisture that
confers on it better keeping qualities.
16. NEW GOVERNMENT FLOURS, DEC. 1916. There is a
considerable variation in the new flours produced by the
' straight run ' process in the different mills.
Some are darker and coarser than others, and appear to
have been rushed through the mill without due regard being
paid to the usual cleanliness.
Bakers will probably experience some difficulty with
1 runny ' doughs and a crumbly texture in the interior of the
loaf unless great care is taken.
A little more salt per sack will prove very helpful in the
matter.
Several loaves that have come under the notice of the
author exhibit the faults as stated above.
INDEX
ABSORBING power of flours, 115,
204.
Acetic or vinegar acid, 22, 79, 80.
Acidic groups, 6.
Acidity of flours, 117, 195.
Acids, classification, definition
and properties of, 22, 79.
Aeration of doughs, 153.
Alcohol a strong poison, 59.
Alcoholic fermentation, theory of,
147-150.
Alcohols, general, 56, 57.
Alkaline carbonates, 11.
waters, 18, 20.
Alkalies, general, 11, 22, 26.
Aleurone cells, 97, 98.
Aluminium compounds, 6.
Alums, their detection, 6, 206.
Amides, 89.
Ammonia in the air, 11, 12.
Analysis of cereal foods, 186, 188.
Antiseptics, 22-26, 131, 172-174.
Apatites, 25.
Ash of wheat, 28, 100.
the estimation of, 189.
Asparagin, 89, 90.
Atmosphere, 10, 11, 13, 32.
Atomic weights, list of, 5.
Atoms, theory and weight of, 4.
Auto-fermentation of yeast, 150.
BACTERIA, 9, 13, 24, 126-131.
Bakers' oven pyrometers, 32.
Bakery physics, 30.
Baking, effect of, 167.
Barley, 1, 100.
Barms, general, 145, 146.
for military sponges, 162.
the making of, 146, 147.
Barometers, 32, 33.
Basic lead acetate, 27.
salts, 27.
Bibliography, 217-218.
Bicarbonates of lime and mag-
nesia, 17.
of soda, 4, 25, 153.
Biology in breadmaking, 8.
Biose sugars, 66-70.
Bisulphites as germicides, 25,
174.
Black of Edinburgh, 11.
Bleaching of grain, 25.
plant for, 108, 109.
tests, 207.
Bloom of bread, 24.
Blue-bag, 6.
Borax to soften waters, 17.
Boric or boracic acid, 22, 25.
Botany in breadmaking, 8.
Brackish waters, 17, 18.
Bread, composition of, 170.
examination, 207.
improvers, 29.
machinery for, 171.
processes, 153, 155.
pure and wholesome, 20.
the chemical analysis of, 208.
Break rolls, 106.
Breaking up of yeast, 161.
Brewing processes, 58.
Brine, settled, 23.
Brown breads, 169.
Buchner on fermentation, 149.
Burton waters, 17, 19.
Butter, 28, 81.
salt, 23.
Butyric acids, 81.
Butyrin, or tributyrin, 28, 85.
CALCAREOUS waters, 18, 19.
Calcium carbonate, 6, 12.
phosphate, 29.
sulphate or gypsum, 16, 21.
Calorimeters, 30.
226
CHEMISTRY OF BREADMAKING
Carbohydrates, 55, 59, 61.
Carbohydrate food, 8.
Carbonates of soda, 17, 153.
Carbon dioxide, 4, 5, 11-13, 22,
25, 29, 155.
Caryopsis, 91.
Caustic soda, 26.
Celluloses, 71, 78, 202.
Centigrade thermometer, 31.
Cereals, examination of, 193.
as grain producers, 91.
their chemical composition,
98, 99.
Cereal starches, 74.
Chemical affinity, 4, 7.
analysis of cereals, 194.
of flour, 205.
combination, laws of, 4.
composition of air, 10, 12.
of bread, 170.
of cereals, 99.
of water, 14.
compound, 3.
equation, 4.
reactions, 5.
Chemistry, inorganic and organic,
2.
Chili saltpetre, 24.
Citric acid, 83, 84.
Cleaning processes, for wheat,
102-105.
Clinkers, how to avoid, 179.
Colloids, their structure, 76, 114,
125.
Colour of the crumb of bread, 168.
of flours, 112, 113, 203.
Combustion of carbon, 12.
Conditioning of wheat, 102.
Conduction of heat, 3, 43.
Conservation of energy and
matter, 4.
Convection, 44, 45.
Cooling of bread, 167.
Copper-reducing power of sugars,
64, 65, 199, 214.
Cream of tartar, 4, 28, 153.
powders, 25.
Cryptogamia,, 9, 126.
Crystalloids, 76.
Cutting back of doughs, 161.
DALTON, Dr. John, 4.
Decay, definition of, 148.
Degree of moisture, 13.
Density, maximum, of water, 15.
of steam, 15.
Derbyshire water, 17.
Dextrins, 76, 77.
determination of, 196, 197,
200.
Dextrose, 61, 62, 199.
Diastase, 75, 209.
pastes, 120, 121, 123.
Diastatic capacity, determination
of, 210, 211.
Dough mixer, 164, 171.
Dried milks, and their analysis,
216.
Drinking water, 14.
Droitwich brine baths, 20.
Dry ness, action of, on flours, 116.
Dutch yeasts, 144.
EARTH'S crust, weathering of, 28.
Edinburgh water, 20.
Electrical pyrometer, 32.
Electrolytes, action of, 114.
Elements, 3.
names of, 4, 5.
Emery, in grinding, 6.
English mineral springs, 20.
Enzymes, or soluble ferments, 88,
125.
their detection, 209.
Enzyme theory of fermentation,
148, 149.
Epsom salts and mineral springs,
20.
Esters or compound ethers, 28.
Eumycetts, 126, 130.
Extractive properties of waters,
21.
Extract of malt, uses of, 122.
FAHRENHEIT thermometer, 31, 32.
Fancy breads, 169.
Fats as bread improvers, 86.
estimation of, 190-192.
general properties, 84, 85.
in germ of cereals, 86, 87.
the composition of, 28.
Fehling's solution, 199.
Ferment and dough process, 155.
156.
Fermentation, definition of, 148.
Ferments, 125.
INDEX
227
Fibre or husk estimation, 202.
Fisheries salt, 23.
Fixed acidity, 79, 82.
fats, 84.
Flavour of bread, 23.
Flour analysis, 203.
Flours, and meals, 110-112.
their properties, 112-118.
classification of, 117.
suitable for short-processes,
160.
suitable for sponges, 159.
Flowers of sulphur, 7.
Food-stuffs, preservation of, 26.
value of bread, 2.
Foreign substances in flour, 205.
Fructose or fruit sugar (Isevulose),
63.
Fuels, 178, 179.
GALACTOSE sugar, 64.
Galileo, 10.
Gaseous bodies, 2, 3.
Gases of the atmosphere, 14.
solubility of, 16.
Gas-evolving power of yeast, 152.
Gay-Lussac's equation, 148.
Gay-Lussac on the composition of
water, 14.
Germ, 98.
analysis and composition of,
101, 208, 209.
Germicides, 24, 25, 26.
Glauber's salt, 20.
Gliadin, 89.
Glucoses, preparation and pro-
perties of, 62, 63.
Gluten, 87-89, 114.
estimation of, 203.
Glutenin, 89.
Glycerin and glycerides, 28, 85.
Graduation of thermometers, 30.
Gramineae, 91.
Grasses, the parts of, 91.
Gums, the, 78.
Gypsum or sulphate of lime, 3, 7,
16-18, 21.
HAMPSON and Linde" on liquid
air, 14.
Harden, Dr. A., on fermentation,
149.
Hardness of water, 16, 21.
Hardy on the strength of flours,
114.
Harrogate waters, 20.
Heat, application and effects of, 7.
calculations, 35-37.
definition of, 42.
latent, 15.
propagation of, 43.
units, 15.
Heating of ovens, 182-185.
Hilum, 72.
Hooke and Mayow on fermenta-
tion, 10.
Hops, bleaching of, 25.
use of, in barms, 146, 147.
Humidity, relative, 13, 30.
Humphries on milling wheats,
105.
Hydrochloric acid or spirits of
salt, 22, 23.
Hydrogen, a constituent of acids,
27, 28.
of water, 14.
Hygiene and antiseptics, 172-174.
Hygrometer, 32.
Hyphomycetes, 131.
IMAGES, the formation of, 47.
Inorganic chemistry, 2.
constituents of cereals, 28.
Intensitj r of heat, 30.
Invert sugar, its preparation and
properties, 64, 65, 199.
Iron, heated with sulphur, 8.
KEUPER Beds, 17.
rnarls, 19.
Krypton gas, 11.
LACTIC acid, 22, 81.
Lactose or milk sugar, 70.
Lsevulose, 63, 199.
Latent heat, 15.
Laundries, and the ultramarines,
6.
Laurent polarimeter, 52, 197.
Laws of chemical combination, 4.
Lead basic salts, 27.
Leaden pipes and soft water, 18.
Leamington mineral waters, 20.
Leaven, 153.
Lenses, 46.
Light action as a germicide, 173.
228
CHEMISTRY OF BREADMAKING
Light metals form bases, 6.
the theory of, 46.
Lignoses, the, 78.
Lime, carbonate of, 6, 12.
phosphate of, 29.
Limestone waters, 17.
Liquid air, 14.
Litmus, a vegetable dye, 22.
London air, 10.
chalk waters, 19.
Lovibond's tintometer, 113.
MABLETHORPE'S saline waters, 17.
Magnification of lenses, 49, 50.
Maize, 73, 100.
Malic acid and malates, 82.
Malt extracts, 120-123.
flour, 119, 124.
and extracts, the
analysis of, 210.
sugar or maltose, 69, 70, 199.
Malting, 118, 119.
Manchester air, 10.
water, 18.
Mason's psychrometer, 32.
Mathematics, 9.
Matter, the composition of, 2.
the conservation of, 4.
Maximum density of water, 15.
and minimum thermometers,
30, 32.
Meals, 109-111.
Mechanical mixture, 7.
Mechanics in a bakery, 38-41.
Media for bacteria, 129.
for moulds, 133.
for yeasts, 138.
Mediterranean sea-water, 23.
Mercurial thermometers, 30.
Metabolism of yeasts, 149.
Metallic salts, 27.
Metals, general, 3, 6.
and non-metals, table of, 5.
Metric system of weights and
measures, 33-35.
Micron, 127.
Micro-organisms, 125.
Microscopes, compound, 47-50 ;
use of, 193, 205.
Military sponges, 161.
Milk analysis, 214.
sugar, 70.
Milling of grain, 1, 102-110.
Milling, machinery for, 106-110.
Mills, hand-stone, 2.
Mineral acids, list of, 22.
constituents of wheat asb,
28, 100.
phosphates for spraying
flour, 29.
salts in water, 16, 17.
springs and waters, 20.
Minnesota wheat, 96, 159.
Moisture, degree of, 13.
estimation, 188.
and total solids in malts,
212.
Molecules, definition of, 2.
Monoses, 61.
Moulds, 132, 133.
reproduction of, 133, 134.
Mucedines, 132.
Mucora, 133.
My corny cetes, 134.
NANTWICH brine springs, 20.
Natural borates as antiseptics,
25.
Neutralising of alkalies, 22.
New Red Sandstone rocks, 17.
Nicol's prism, 52.
Nitric acid and nitrates, 24.
Nitro-celluloses, 79.
Nitrogen gases, 11.
in air, 10, 12, 13.
Nitrogenous bodies, estimation
of, 192, 193.
constituents of wheat, 87.
Non-metals or metalloids, 2, 3.
list of, 5.
sources of, 6.
Normal salts, 26, 27.
Noxious exhalations, 11.
Nucleins, 87, 90.
Oidium, 132, 134.
Olein, a fat, 28.
Olive oil, 28.
Opticity, 52, 196.
Organic acids, 79.
chemistry, 2, 55.
constituents of cereals, 55.
impurity in water, 17.
Osmosis, 125.
Ovens, kinds of, 180-185.
Over- fermentation, 165.
INDEX
229
Oxalic acid and oxalates, 22.
Oxides and oxyacids, 29.
Oxygen an element, 3.
in air, 10-13.
in water, 13, 14.
PASCAL, 10.
Pasteur's pure yeast, 173.
Peel oven, 181.
Pekar test for flours, 113, 203.
Penicillium, 133, 134.
Peronospora, 132.
Phenol, 172.
Phosphates, as bread improvers,
29.
estimation of, 190.
Phosphoric acid and phosphates,
22, 25, 27, 100.
Physical forces, 4.
Physics, 7.
Pliny, 1, 168.
Polarimeters or polariscopes, 50,
51, 197.
Polarimeter of Laurent, 53, 54,
197.
Polarised light, 52, 72.
Polyoses or polysaccharidea, 71-79.
Potassium saltpetre or nitre,
solubility of , 16.
Potato ferments, 155.
Preservation of foods, 26.
Prisms, Nicol's, 52.
Proteids, 87, 89, 192, 216.
Proteins and soft water, 21.
Proteolytic enzymes, 88.
Protoplasm, 127.
Proving of doughs, 166.
Proximate food principles, 2, 98,
99.
Psychrometer, 32.
Pure water, 14.
Purity of a flour, 117.
Putrefaction, definition of, 148.
Pyrometers, 32.
QUANTITIES of material for
straight doughs, 163.
Querns, 2.
RADIATION of heat, 45.
Raffmose, 71.
Red Sandstone rocks in Cheshire,
17.
Relative density, 16.
humidity of the air, 13.
Retarding effect of gypsum, 21.
Rochelle salt, 4, 154.
Rolls, 106, 108.
Rye, 73, 100.
Saccharomyces, 141.
Saline waters, 18.
Salt, uses in a bakery, 23.
manufacture of, 23.
Salts, classes of, 26, 27.
Scales of thermometers, 31.
Schizomycetes, 126, 130.
Schmidt-Haensch polarimeter, 54,
197.
Semolinas, 29.
Setting of bread in ovens, 166.
Shelf oven, 180.
Side-flue oven, 181.
Siemen's electrical pyrometer, 32.
Silica estimation, 189.
Siliceous waters, 18, 19.
Sixe's thermometer, 30.
Soaps, composition of, 86,
Sodium chloride or salt, 23.
Sodium nitrate or Chili saltpetre,
5.
Soft and alkaline waters, 20.
Solids, determination of, 212, 214.
Solubility of nitre, 16.
Soluble extract of cereals, 194.
Solvent power of water, 16.
Soxhlet fat extractor, 191.
Specific gravity, 3, 212.
rotatory power, 52, 196.
Specific heat and calculations, 37,
38.
Spirits of wine, 58, 59.
Sponge and dough processes, 156-
162.
Stability of flours, 116.
Starches, estimation of, in cereals,
201.
extraction of, 73.
general, 72.
granule structure, 72, 73.
gums or dextrins, 76, 77.
properties of, 74-76, 125.
Stas and Dumas, 14.
States of matter, 2, 22.
Steam, density of, 15.
Steam-pipe oven, 182.
230
CHEMISTRY OF BREADMAKING
Sterile appliances in a bakery,
175.
Straight dough processes. 155. 162-
164, 169.
Strength, definition of, 115, 203.
of flours, 114, 115.
Succinic acid, 82.
Sucroses, general, 66.
properties of, 69.
Sugars, 3, 6, 61-71.
estimation of, 196, 213.
refining, 67.
Sugar chars, composition of, 68.
Sulphuric acid, 6, 22, 24.
Sulphurous acid and sulphites,
25.
Super-phosphate in cream pow-
ders, 25.
Symbols, chemical, 4, 5.
TABLE or butter salt, 23.
Tartaric acids and tartrates, 22,
82, 83.
Temperature of doughs, 170.
of inside of loaf, 167.
of water for yeast, 161.
Thermometers, general, 30, 31.
a necessity, 161.
Thermometric scales, 31, 32.
Thymol, 172.
Time sponges, 161.
Tin bread and salt, 24.
Torricelli, 10.
Triglycerides, 85.
Triticum, 91, 94.
Tunbridge Wells iron waters, 20.
ULTRAMAKINES, 6.
Unit, British thermal, 15.
Unleavened bread, 1.
VEGETABLE acids, 22.
sources of organic matter,
13.
Ventilation in the bakery, 175-
177.
Vienna oven, 184.
Virtual images, 47.
Viscosity time of doughs, 205.
Vitriol, 8-23, 24.
Volatile fats, 84.
Volume of oxygen in air, 10, 11.
of water, changes in, 15.
WAGON oven, 181.
Warmth, action of, on flours, 116.
Wash, distillery, 145.
Water-absorbing power of flours,
115.
Water barometers, 33.
boiling point of, 31.
general, 14-21.
testing, 186, 187.
vapour in air, 12.
Weak flours, to strengthen, 29.
Weathering of rocks, 16.
Wedgewood's pyrometer, 32.
Weight of air, 10.
of an atmosphere, 33.
Weights atomic, 5.
relative, 4.
Wheat, chemical composition of,
99.
classification of, 94, 95.
English varieties, 95, 96.
examination of, 193.
flower and its parts, 92, 93.
spring and winter, 96.
structure of berry, 96, 97.
White loaf, 2.
Wood, Prof., on volume, 165.
Wood spirit, 57, 58.
YEASTS, 8, 21, 24, 134-145.
ash of, 139.
brewery, distillery, and
vinegar, 142.
classification of, 140.
culture apparatus, 141.
examination of, 150-152.
reproduction of, 137, 143.
structure of, 135, 136.
ZINC sulphate, or white vitriol,
26.
Zooglceal state, 131.
Zoology, 8.
Zymase, 149.
Printed by T. and A. CONSTABLE, Printers to His Majesty
at the Edinburgh University Press
OVERDUE.
LD 21-lOOw-8,'34
YB 67824
UNIVERSITY OF CALIFORNIA LIBRARY
