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U. S. DEPARTMENT OF AGRICULTURE,
issued January ft, lOOt).
BUREAU OF CHEMISTRY— BULLETIN No. 119.
H. W. WILEY, Chief of Bureau.
EXPERIMENTS ON THE SPOILAGE
OF TOMATO KETCHUP.
BY
A. W. BITTING,
INSPECTOR, BUREAU OF CHEMISTRY,
WASHINGTON:
GOVERNMENT PRINTING OFFICE.
1909.
Issued January 9, 1909.
U. S. DEPARTMENT OF AGRICULTURE,
BUREAU OF CHEMISTRY— BULLETIN No. 119.
H. W. WILEY, Chief of Bureau.
EXPERIMENTS ON THE SPOILAGE
OF TOMATO KETCHUP.
BY
A. W. BITTING,
INSPECTOR, BUREAU OF CHEMISTRY.
WASHINGTON:
GOVERNMENT PRINTING OFFICE.
1909.
LETTER OF TRANSMITTAL.
U. S. Department of Agriculture,
Bureau of Chemistry,
Washington, B.C., July 15, 1908.
Sir: I have the honor to submit for your approval a report made
by Inspector Bitting of experimental work on the spoilage of tomato
ketchup, the conditions contributing thereto, methods of prevention,
the action of preservatives, and the length of time that the product
will keep under varying conditions of manufacture and temperature,
both before and after opening. Every effort has been made to
conduct the work in a practical way, and the results obtained can
not fail to be of interest and profit both to the manufacturer and
consumer. I recommend that this report be published as Bulletin
No. 119 of the Bureau of Chemistry.
Respectfully, H. W. Wiley,
Chief.
Hon. James Wilson,
Secretary of Agriculture.
CONTENTS.
Page.
Introduction 7
Process of manufacture 8
Selection and preparation of stock 9
Pulping 9
Cooking and seasoning 10
Evaporation and finishing. 11
Bottling 11
Processing ] 1
Character of products 12
First-class products 12
Inferior products from "trimming stock " 13
Labels 14
Manufacturing experiments without the use of preservatives 15
Outline of experiments 15
Discussion of results 17
Spoilage of ketchup after opening 17
Spoilage of unopened ketchup 20
Spoilage of market brands 20
Sterility of ketchup 21
Experiments with preservatives 22
Sodium benzoate 22
Salt 23
Sugar 23
Spices 24
Water infusions 24
Acetic acid extracts •. 25
Oil extracts 25
Vinegar and acetic acid 26
Oil 27
Study, of Penicilliam in ketchup 28
Development t 29
Reproduction 29
Growth in ketchup 30
Temperature tests 31
Histological structure of ketchup 33
Microscopical examination of some commercial brands 34
Summary 35
5
ILLUSTRATIONS.
PLATES.
Page.
Plate I. Penicillium. Fig. 1. — Conidia, normal growth and in various stages
of germination, some with branching hyphae. Fig. 2. — Conidio-
phore, showing unusually large development of conidia; from cul-
ture in moist chamber 28
II. Cultures from ketchup preserved with sodium benzoate. Fig. 1. —
Conidia and hyphae from culture in experimental ketchup con-
taining one-sixteenth of 1 per cent of sodium benzoate. Fig. 2. —
Conidia and hyphae from culture in experimental ketchup contain-
ing one-tenth of 1 per cent of sodium benzoate 28
TEXT FIGURES.
Fig. 1. A model receiving platform 8
2. Large receiving room showing the sorting belt 9
3. A section of a kitchen showing the copper cookers 10
4. An example of factory practice 12
5. Another factory interior 14
6
EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP.
INTRODUCTION.
The tomato, Lycopersicum esculentum, is supposed to be native to
South or Central America. The large fruits commonly used grow
only under cultivation, but the variety with small, spherical fruits,
known as L. cerasiforme, has been found on the shore of Peru and is
considered by De Candolle a as belonging to the same species as
L. esculentum. Though grown extensively in Europe, there is nothing
to indicate that it was known there before the discovery of America.
The tomato was introduced into China and Japan at a comparatively
recent date. De Candolle is of the opinion that the tomato was
taken to Europe by the Spaniards from Peru and was later introduced
into the United States by Europeans. Tomatoes were brought to
Salem, Mass., by an Italian painter in 1802,6 who is said to have had
difficulty in convincing the people that they were edible. They were
used in New Orleans in 1812, though as late as 1835 they were sold by
the dozen in Boston. After 1840 they came into general use in the
Eastern States, but it was later than this before tomatoes were used
freely in the Western States, many persons having the impression that,
since they belonged to the nightshade family, they must be un-
wholesome. The extent to which tomatoes are used at the present
time shows how completely this prejudice has been overcome.
The name Lycopersicum is from two Greek words, meaning a wolf,
and a peach, the application of these terms not being apparent; the
name of the species, esculentum, is from the Latin, meaning eatable.
The common name " tomato" is of South or Central American origin,
and is believed to be the term used in an ancient American dialect to
designate the plant,c but its meaning is unknown. The English call
the tomato "love apple," which in French is "pomme d' amour."
The tomato is considered a typical berry, the ovary wall, free from
the calyx, forming the fleshy pericarp, which incloses chambers filled
with a clear matrix containing the seeds. The fruit measures from 1
to 5 inches in diameter, and is red, pink, or yellow when mature.
The plant sports freely, producing many varieties, which differ
mainly in the size, shape, and quality of the fruit. The varieties
a Origin of Cultivated Plants, 1890.
& Webber, H. J., Yearbook, IT. S. Department of Agriculture, 1899.
cV. S. Dept. Agr., Exper. Sta. Record, 1899-1900, 11: 250.
8 EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP.
bearing small fruits are L. cerasiforme and L. pyriforme, each bearing
a two-celled fruit, the former being round, and somewhat larger than
a cherry, and the latter pear-shaped. These small tomatoes are used
ordinarily for preserves and pickles.
The word " ketchup" is adopted in this bulletin as the form which
ought to be given preference. The derivation of the term is not defi-
nitely known. The spelling " catchup" given in some of the leading
dictionaries appears to be based on the erroneous idea that the first
syllable " ketch" is a colloquial form of " catch." Several authori-
ties derive the word from the East Indian or Malayan " kit jap,"
because "ketchup" was originally a kind of East Indian pickles.
Some give the word a Chinese origin, while others assert that it comes
from the Japanese. A majority of the manufacturers employ word
"catsup," a spelling for which there does not appear to be any
warrant.
PROCESS OF MANUFACTURE.
The making of tomato ketchup consists essentially in reducing
tomatoes to pulp, removing the skins, seeds, hard parts, and stems,
adding salt, sugar, condiments, and vinegar to suit the taste, and
Fig. 1. — A model receiving platform.
cooking to a proper consistency. The methods and practices of the
various manufacturers differ, and the difference between the best
and the poorest procedure corresponds to that between the best and
the worst ketchup. No single factory has all of the best methods
at every step of manufacture. Some perform certain details well
and are negligent in others. In some, large amounts of money are
PKOCESS OF MANUFACTURE.
9
spent on equipment to improve a particular point considered advan-
tageous by the trade, while other details essential to the making of
a good-keeping ketchup are disregarded. A statement of the best
practice as observed at a number of factories, together with some
facts obtained from experiments, will be given.
SELECTION AND PREPARATION OF STOCK.
The tomatoes should be home-grown, of a red variety having the
minimum of yellow and purple color, be picked when ripe, and deliv-
ered to the factory promptly without mashing. All tomatoes should
pass over an inspection table, the rotten and otherwise unfit fruit
Fig. 2.— Large receiving room showing the sorting belt.
should be discarded, and the green tomatoes should be returned to
crates to ripen. The stems should be removed when the best color
is desired, and the tomatoes should be thoroughly washed to remove
dirt and mold. Dumping a crate of tomatoes into a hopper of dirty
water and playing a gentle spray of water on part of them merely
wets the skin and makes them appear bright.
PULPING.
The clean tomatoes should be conveyed to the steaming tanks
and subjected to steam heat until the skins burst and the meat
softens. After a short heating the tomatoes should be run through
a " cyclone " where the skins, seeds, etc., are removed and they are
57211— Bull. 119—08 2
10
EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP.
rubbed to a pulp. To remove very small particles and fiber, the
pulp may be run through a sieving machine at once; or, if ketchup
of the smoothest possible kind is to be made, this procedure should
be delayed until after the cooking. The pulp is collected in a receiv-
ing vat, and only such an amount should be provided in advance as
will keep the kettles full, as it is better to stop the tomatoes before
going to the washer than to have the pulp stand for some hours.
In common practice, however, the pulp is either sent to the cooker
at once, or it is allowed to stand and partially separate. If tall
casks are used for this separation the solids will rise to the top
and the clear watery portion is drawn off at the bottom, or the
pulp may be strained through cloth bags. The object of this sepa-
ration is to secure greater concentration of the solids, retain a
brighter color, and shorten the time of cooking.
COOKING AND SEASONING.
The cooking may be done in copper kettles, as shown in figure 3,
though these are being superseded by enamel tanks containing silver-
plated coils in order to secure the brightest color. By using the
Fig. 3.— A section of a kitchen showing the copper cookers.
latter the discoloration due to the splashing of the contents against
the walls of the copper vessel is avoided, and economy of space is
secured. Whole or ground spices, or acetic acid or oil extracts of the
spices may be added to the pulp in such proportion as the particular
brand demands. The spices most used are cloves, cinnamon, mace,
and cayenne pepper; but paprika, pepper, mustard, cardamon,
PROCESS OF MANUFACTURE. 11
coriander, ginger, celery, and allspice are used by some manufac-
turers. When whole spices are used, it is the practice to suspend
them in a cloth bag or a wire basket and to take them out after
boiling. They tend to darken the color of the ketchup, a result
considered undesirable by some. The ground spices are used spar-
ingly, with the exception of cayenne pepper. The acetic acid extracts
of spices are used because they are economical and give a brighter
red color than is obtained with the whole spice. The oil extracts
produce no discoloration, but they are the most expensive and give
an objectionable flavor. Hungarian sweet paprika is now quite
largely used and adds to the color as well as to the flavor. Sugar,
salt, and vinegar are added in such proportion as may be desired,
and in some brands onions and garlic are used.
EVAPORATION AND FINISHING.
The pulp is evaporated rapidly to such consistency as the grade
and price will warrant, the reduction in volume being from 40 to 60
per cent. This is accomplished in about forty-five minutes. The
cooking is not continued longer than is necessary, as each minute
added to the cooking darkens the finished product.
If the pulp has been run through the sieving machine before cook-
ing, the batch may be drawn off into the receiving tank for bottling.
If the finishing be done after cooking, the pulp is run into a receiving
vat, finished as quickly as possible, and drawn into the tank for
bottling. The ketchup may be kept at a high temperature — 200° to
206° F. — in the receiving tank by means of a small steam coil, or it
may be drawn to the bottling machine through a steam-jacketed tube.
Finishing after cooking yields a slightly smoother ketchup than
sieving before cooking; but it necessitates handling, reduces the
temperature, and increases the chances of infection.
BOTTLING.
The bottles should be thoroughly cleaned as ketchup will not
keep if placed in bottles which have been merely rinsed to remove
the straw; if the ketchup is not to be given an after process the
containers should be sterilized. In the experimental work cork
stoppers gave the best results and these should be sterilized in a
paraffin bath at 250° F.
PROCESSING.
An after treatment or process is given to bottled goods either in
a water or steam bath, the important point being that the center
of the bottle be raised to the desired degree of heat. If the
ketchup is thin this can be effected quickly, but if it is thick and
heavy the heat penetrates the ketchup with surprising slowness.
12
EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP.
In a thin ketchup the temperature may be raised from 140° to
190° F. in eighteen minutes or less when the surrounding heat is
195° F.; but in a heavy ketchup it may take an hour or more to
accomplish the same result. It is therefore very important that
Fig. 4.— An example of factory practice showing the top row of tanks from which pulp passes by
gravity into the cookers, then into the receiver, sieving machine, and final tub ready for the bot-
tling machine or jug filler.
the ketchup be processed immediately after it is corked, before it
has time to cool. The rate at which the heating is effected for
different goods can be determined by sealing a thermometer in
the cork and recording the readings.
CHARACTER OF PRODUCTS.
FIRST-CLASS PRODUCTS.
The factory at which the experiments were conducted has sanitary
buildings and surroundings, the floors are of concrete for flushing,
and the pipes used in conducting the pulp to the kitchens are porce-
lain-lined to prevent discoloration from the iron and to insure
cleanliness. The tubes which carry the ketchup from the kettles
to the receiving tank, finishing machine, and bottler are silver-plated.
CHARACTER OF PRODUCTS. 13
Not all of these measures are necessary to make a good ketchup, but
they show the care exercised in making an article of good appearance
and of the finest quality.
The conditions under which ketchup is made and the care with
which the work is done at some of the better factories is equal to
that used in the manufacture of any food product. Whole selected
fruit is used, cleanliness is maintained at every point, the best grades
of spices, vinegar, granulated sugar, and salt are added for flavoring,
and the bottles are carefully washed. The ketchup put up under
such conditions will have a bright natural color, will remain good as
long as the container is unbroken, and will continue in that condition
for some time after opening if kept at a fairly cool temperature.
INFERIOR PRODUCTS FROM "TRIMMING STOCK."
In contrast with the strictly high-grade product is the great bulk
of the ketchup found on the market. The material is not whole
ripe tomatoes, but consists of the waste of the canning factory,
commonly designated as " trimming stock/' including the green,
moldy, broken, rotten, and generally unusable tomatoes, the skins,
cores, and stems from the peeling tables, and the surplus juice from
the filling machines, all of which may be allowed to stand during the
day and be run through the cyclone in the evening. At the end of the
season, the frosted and half -ripe fruits may be used. Part of this
material can not be considered "sound fruit" as contemplated by the
food and drugs act. The pulp is put up in barrels, preserved, and
allowed to stand, possibly in the sun, until a sufficient quantity has
accumulated for shipment. Old ketchup barrels may be used and
be none too clean. As a result, it is not uncommon to see an inch or
more of pulp in the bottom of a car at the end of shipment, caused
by the blowing out of the barrel heads from fermentation. The
sanitary condition of the factory may be poor, the handling of the
goods be unclean, the spices be the refuse from the spice houses,
the sugar be of the cheapest grade, and the bottles be only rinsed or
be used without even that precaution. The ketchup is a concoction
so heavily spiced with hot spices that the tomato flavor is lost and
might as well be anything else. The color is normally dirty brown.
Between these two extremes are all grades, those for which whole
tomatoes, unsorted, are used, those for which trimming stock is
worked up promptly during the canning season, and those made
from stock of unknown history. Some manufacturers work under
good and some under poor sanitary conditions. There can be no
doubt that with proper selection and precaution much of the -by-
product of the canning factory and large quantities of tomatoes
which are unsuitable for canning might be used to advantage in the
manufacture of ketchup; but it requires a nicety of practice not
14
EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP.
generally found at this time. The practice sometimes followed of
making some ketchup from whole stock and a large quantity from
refuse and using the former for advertising purposes, only serves to
emphasize the fact that the goods belong to two distinct classes. One
of the uses for a very considerable amount of pulp from refuse stock
is the making of sauce for baked beans and other canned goods
where the true character can not be observed by the consumer.
During the season tomatoes come in at times in larger quantities
than can be made into ketchup promptly. The surplus must be
worked up into pulp for storage and may be stored in barrels or in
4
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Fig. 5— Another factory interior, showing large pulp tanks in the rear, cooking tanks on the right,
and process tanks in front containing thousands of bottles of ketchup.
tin cans. The pulp stored in barrels will not have as good a color as
that put into cans, and the ketchup made from either will not be as
bright as that made from whole, fresh stock. The pulp put up in
barrels is more liable to spoilage than that put up in cans. The
difference in the cost of storage by the two methods is not very
great, and some large concerns are using the can exclusively instead
of the barrel.
LABELS.
The labels on the ketchup bottles have been improved somewhat
in the last year as regards exactness in describing the contents. For-
merly, according to the labels, much of the ketchup was made from
EXPEKIMENTS WITHOUT USE OF PRESERVATIVES. 15
whole ripe tomatoes. The question was, What became of the
enormous amount of ketchup which it was known had been made
from " trimmings?" On this year's ketchup the labels make fewer
claims, generally merely stating that it is " tomato ketchup/' which
is true whether made from whole tomatoes or refuse. The brand is
in most cases the guaranty for good quality. It is not safe to judge
the quality by the price, for, though usually good quality can not be
expected unless the higher price is paid, some of the high-priced
ketchup when placed under the microscope has proven to be a very
inferior product.
The wide labels on the neck of the bottle are objectionable. Some
of these are 2 inches in height, and serve to cover the discolored and
spoiled ketchup. As spoilage begins usually in the neck of the
bottle, it is difficult to see it when the neck is wrapped with a label,
and thus it might easily be overlooked until the main body of the
ketchup is affected. The bottles which have the widest labels
around the neck are usually the ones provided with one or two large
labels on the lower part of the bottle, though some bottles have no
other label but the one around the neck. As a rule, however, these
are narrow, close to the stopper, and unobjectionable.
In buying ketchup for experimental purposes it was difficult and
sometimes impossible to learn its age, as often the grocer does not
know it, and at other times he will not tell. It appeared, however,
that often the ketchup had been on the grocer's shelf or in the ware-
house from one to four years.
MANUFACTURING EXPERIMENTS WITHOUT THE USE OF
PRESERVATIVES.
OUTLINE OF THE EXPERIMENTS.
During September, 1907, ketchup was made in experimental
batches to determine whether it could be manufactured on a com-
mercial scale without the use of preservatives. These experiments
were made to determine (1) the keeping quality before opening the
container and (2) the length of time the product will keep without
spoilage after the bottle is opened.
The ketchup was made in a factory in which the conditions of
manufacture and all the surroundings were sanitary; whole, ripe
tomatoes, the same as used in the regular grade of canned goods,
were used and the formula and process were for a mild ketchup
giving the maximum of tomato flavor. Each batch consisted of 50
gallons of finished goods, from which 1 gross of pint bottles was
retained for observation.
The term " regular ketchup" as used in these experiments means
the pulp of fully ripe tomatoes, to which was added granulated
16 EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP.
sugar, 80-grain, distilled vinegar, table salt, onions, garlic, whole
cinnamon, cloves, mace, and ground cayenne pepper. The pulp
was cooked in a steam-jacketed copper kettle for forty minutes and
reduced about 50 per cent. The finishing was done after cooking.
The regular bottles are pint sizes, washed in hot water, rinsed, and
then heated to a temperature of 190° F. for thirty minutes or more.
The sterile bottles referred to in the experiments were placed in a
steam chamber for twenty minutes at 230° F. The corks were
sterilized by a bath in paraffin at about 270° F. All of the work
was accomplished quickly to insure a smooth, even product with a
bright, clean color. Acetic acid extracts and oil extracts of spices
were used in such quantities as would give the same amount of
spicing as when the whole spices were employed.
In all of the following experiments the ketchups discussed were
made in September, 1907, and the last examination reported was
made ten months later, in July, 1908:
Experiment No. 1. — Regular ketchup was made, but it was reheated after finishing
and bottled in sterile bottles at a temperature of 205° F. No spoilage has occurred
at the end of ten months.
Experiment No. 2. — Regular ketchup was made, and it was bottled immediately
after finishing in regular bottles at a temperature of 165° F. An after process was
given at 190° F. for twenty minutes. No spoilage has occurred after ten months.
Experiment No. 3. — Regular ketchup was made, and was bottled in regular bottles
at 165° F., and given a subsequent process at 190° F. for forty minutes. No spoilage
has occurred.
Experiment No. 4- — Regular ketchup was made, was bottled in regular bottles at a
temperature of 165° F., and given an after process at 212° F. for twenty minutes. No
spoilage has occurred.
Experiment No. 5. — Regular ketchup was made, the same being put up in regular
bottles at a temperature of 165° F. and given an after process at 212° F. for fcrty min-
utes. No spoilage has occurred.
Experiment No. 6. — Ketchup was made in which the acetic acid extracts took the
place of whole spices, and the bottling was done at a temperature of 165° F., no after
treatment being given. No .spoilage has occurred.
Experiment No. 7. — Ketchup was made in which acetic acid extracts were used,
and the bottling was done at a temperature of 165° F. in sterile bottles. No after
treatment was given and no spoilage has occurred.
Experiment No. 8. — Ketchup was made in which the oil extracts were used instead
of regular spices. The bottling was done in regular bottles at a temperature of 165° F.,
no after treatment being given. No spoilage has occurred.
Experiment No. 9. — Ketchup was made in which oil extracts were used instead of
whole spices. The bottling was done at 165° F. in sterile bottles, no after treat-
ment being given. No spoilage has occurred.
Experiment No. 10. — Regular ketchup was made, but the pulp was run through
the sieving or finishing machine before instead of after cooking, the object being to
determine the effect upon the character of the goods rather than upon the spoilage.
This practice could be followed to advantage in making all except the very finest
goods, and would give the same condition for bottling as in experiment No. 1.
Experiment No. 11. — Pulp was made in the usual manner and run into barrels
while just below the boiling point. The barrels had been thoroughly washed and then
steamed for twenty minutes. As soon as the pulp had cooled slightly the bung was
EXPERIMENTS WITHOUT USE OF PRESERVATIVES. 17
driven in tightly and the barrel was rolled into storage. At the end of sixty days the
barrels were opened and the pulp was found to be in good condition.
Experiment No. 12. — Regular ketchup was drawn into 5-gallon jugs which had been
sterilized in the same manner as the bottles. These were kept for sixty days and no
spoilage occurred.
DISCUSSION OF RESULTS.
Twelve hundred and ninety-six bottles were shipped from Terre
Haute to Lafayette, Ind., and some were reshipped in order to dupli-
cate the conditions in trade. Some were kept in a warm temperature
and in strong light, others in a comparatively cool place and in the
original shipping cases, in order to duplicate the conditions in the
warehouse and grocery store. There has been no spoilage after ten
months other than that resulting from four or five cork leaks and
neck cracks. These experiments have shown conclusively that
ketchup can be put up on a commercial scale and delivered to the
consumer in perfect condition without the use of a preservative.
It was demonstrated by the first experiment that the goods could
be bottled at a high temperature without difficulty, and that subse-
quent treatment was unnecessary. The after treatment at 190° was
tried because it had been found in small experiments that, in giving
a higher temperature, the internal pressure would cause more or less
breakage of bottles or loosening of corks. After treatment is prac-
ticed by some who also use a small quantity of preservative as a
further precaution. This treatment is continued from two to three
hours at the temperature of high pasteurization.
The process at 212° was given with little breakage, as the bottles
used were of good quality. At and above this temperature the
breakage may be reduced by either raising the temperature of the
ketchup before bottling or applying pressure upon the outside while
giving the process.
Neither the acetic acid nor the oil extracts showed any advantage
over whole spices in their preservative effects, as all kept. The color
was slightly improved, but the flavor was impaired, particularly when
the oil extracts were used.
SPOILAGE OF KETCHUP AFTER OPENING.
The question of how long the ketchup should keep after opening
the container in order to satisfy the ordinary requirements of con-
sumption was also studied. A local restaurant, serving about two
hundred meals and using from one-half to a gallon of ketchup daily,
was supplied with the same kind of ketchup used in the experiments,
as were also some families. Instructions were given to use the
ketchup as they would ordinarily, with the result that none reported
any loss from spoilage.
To determine how long the ketchup would keep after opening, 8
bottles from each of the first 9 experiments were kept in the kitchen
57211— Bull. 119—08 3
18 EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP.
at a temperature of about 72° F., 5 were kept in an incubator at a
temperature of 95° F., 5 were kept in the laboratory at a tempera-
ture of about 67° F., and 4 were kept in an inclosed porch where
the temperature ranged from 30° to 60° F. This made a total of
198 bottles. No precautions, other than those of ordinary clean-
liness, were taken in opening the bottles, as it was desired to deter-
mine the keeping properties under conditions of general usage. The
first set of bottles was opened November 5, immediately on being
received at the laboratory, all of the ketchup having been kept at
the factory until the experiment begun in September was completed.
The bottles were covered loosely with a metal cap and observed daily,
a record being kept of the date and character of spoilage.
The results showed that the differences in the time and temperature
of processing had little, if any, effect in checking the spoilage; neither
did the use of acetic acid or oil extracts. The most important pre-
caution in checking the spoilage after opening seems to be to keep
the ketchup cool. This is shown by the average number of days
which elapsed before spoilage occurred in the sets kept under different
temperature conditions. For those kept in the kitchen the average
number of days was six, the minimum three, and the maximum
eleven. Those in the incubator kept for an average of five days, with
a minimum of two days, and a maximum of eight. Those in the
laboratory had an average of eight days, the minimum being four
days and the maximum twenty-two. Those kept in the porch lasted
on an average twenty-seven days, a minimum of twelve days, and a
maximum of fifty-eight.
These figures show the definite relation of temperature to spoilage
under the conditions of ordinary use. In making the observations,
the metal cap was removed each day, but no ketchup was poured off.
The spoilage in all cases was due to mold, and usually this formed in
the neck of the bottle where the ketchup had splashed, or at the
junction of the ketchup with the bottle. The spoilage was recorded
as soon as the slightest growth appeared. In actual use if the neck
were wiped out when the ketchup had been used and a growth of
mold removed on its first appearance witli some of the proximate
ketchup the time before spoilage occurred could be prolonged. In
these experiments the attempt was made to determine how soon
growth appeared under the various conditions of temperature named.
The unopened bottles of ketchup were kept in a basement room,
the temperature of which is fairly constant, being about 70° F.
This is approximately the condition in a grocery where the ketchup is
kept on the shelves. Another set of samples from the run of Sep-
tember, 1907, was opened February 11, 1908, to determine if storing
in a warm room before opening had any effect on the length of time
preceding spoilage. Four bottles were taken from each of the first 9
experiments to make up each of three sets, one of which was kept in
EXPERIMENTS WITHOUT USE OF PRESERVATIVES.
19
the kitchen, one in the incubator, and one in the porch, making a
total of 108 bottles. The average number of days for those kept in
the incubator was four, the minimum two, and the maximum six.
The average number of days before spoilage in the kitchen was five,
the minimum being three and the maximum nine. Those kept in
the porch gave an average of twenty-three days, the minimum num-
ber being eighteen days and the maximum seventy- three days.
Thus it is seen that the ketchup lasted nearly five times as long at a
temperature of 30° to 60° F. as it did at 72°; and also that when
ketchup is kept in a warm place before opening, spoilage occurs
somewhat sooner, the average for the fresh samples opened under
the same conditions being one day more with the incubator and
kitchen samples and four days more with the porch samples.
A third set of bottles of the ketchup was opened on June 6, 1908,
or two hundred and sixty-five days after manufacture. They had
been kept in a basement at a temperature of about 70° F.
One set was placed in the incubator at a temperature of 95° F., one
set in the kitchen at about 82° F,, and one set in the refrigerator at
46° F. The weather was warm and the conditions favorable to the
spoilage of fresh foods. The minimum time for spoilage in the incu-
bator was two days, the maximum time four days, and the average
time three and two-tenths days. The minimum time in the kitchen
was two days, the maximum time six days, and the average time
four and four-tenths days. The minimum time in the refrigerator
was nine days, the maximum time nineteen days, and the average
time thirteen and sixty-six one-hundred ths days.
These data are grouped in the following table for easier comparison:
Time of spoilage of ketchup at different temperatures after opening.
OPENED ON NOVEMBER 5, 1907, IMMEDIATELY UPON RECEIPT FROM FACTORY;
MAXIMUM AGE, FIVE WEEKS.
Place of storage.
Incubator. .
Kitchen
Laboratory
Porch
Tempera-
ture.
Lapse of time before spoilage.
Average. Minimum, i Maximum.
F. Days.
95 5
72 6
(17 8
30-60 27
Days.
Days.
KEPT AT 70° P. FOR ONE HUNDRED AND FIFTY DAYS BEFORE OPENING ON
FEBRUARY 11.
Incubator
95
72
30-60
4 2 6
5 3 9
Porch
23 is 73
KEPT AT 70° F. FOR TWO HUNDRED AND SIXTY-FIVE DAYS BEFORE OPENING ON
JUNE 6.
95
82
46
3.2 2
4.4 2
13.66 9
1
4
6
19
20 EXPEBIMEKTS ON THE SPOILAGE OF TOMATO KETCHUP.
SPOILAGE OF UNOPENED KETCHUP.
Another test was made to determine whether the ketchup would
spoil when kept in a warm place, but not opened. Three bottles
from each experimental batch were placed in the incubator Novem-
ber 7, 1907, and were kept there until December 23, 1907 — forty-six
days — and in that time there was no sign of spoilage. They were
then opened and kept in the laboratory; the average number of
days before spoilage occurred is indicated in the following table:
Average number of days before spoilage of ketchup after opening (kept 46 days at 95°
before opening).
Experiment No.
Days be-
fore
spoilage.
Experiment No.
Days be-
fore
spoilage.
1
2§
3J
5
H
6
7
4£
4*
il
3§
2
3
8....\
9
4...
5
It will be observed that these samples spoiled in about the same
length of time as the bottles opened in February and tested in the
incubator, so that similar results were obtained by keeping unopened
ketchup one and one-half months at 95° F. and keeping it five
months at 70° F. From the results of the experiments it is evident
that the ingredients of the ketchup in the proportions used are not
antiseptic, and it is also apparent from the number of organisms
found and the rapidity of their multiplication that ketchup is a good,
nutritive medium. Yeasts and molds are the predominating organ-
isms, and, as the ketchup is acid and also contains sugar, and these
organisms are found on tomatoes in the field, their predominance in
the ketchup is explained.
SPOILAGE OF MARKET BRANDS.
To determine the keeping properties of the ketchup on the market,
various brands were obtained from the grocery stores. In the
majority of cases nothing was known of the ingredients or methods
of manufacture, except what appeared on the labels. No date of
manufacture was given, and in some cases the dealers did not know
the age of the product.
There were 104 bottles of ketchup opened to find out how long they
would remain in good condition. These were kept in the laboratory,
though the temperature was higher than that at which ketchup
should be held. Of the 104 bottles there were 66 without preservative,
according to the labels, 46 of which spoiled. Of the 20 which did not
spoil, 2 formed crystals of benzoic acid on the covers of glass dishes
EXPERIMENTS WITHOUT USE OF PRESERVATIVES. 21
during evaporation. Of the 39 which, according to the labels, con-
tained sodium benzoate, 15 spoiled. The bottles of unspoiled ketchup
after remaining in the laboratory for about a month were placed in the
incubator at 95° F. for three weeks, and were then taken out, and
have been left in the laboratory since. The metal cap had been taken
off frequently for observation, and the ketchup exposed, but the
treatment did not cause them to spoil.
The average number of days after which spoilage occurred for the
46 bottles without preservative was about fifteen, the minimum
number being four days, the maximum number ninety-four days.
The average number of days preceding spoilage in the case of 15 bot-
tles with preservative was twenty-four days, the minimum number
being three and the maximum sixty days. The majority of these had
0.1 per cent of sodium benzoate present; the others had a smaller
amount, according to the manufacturer's label. These data are
not at all conclusive and further work on material of known his-
tory will be necessary.
STERILITY OF KETCHUP.
To determine the sterility of ketchup, cultures were made from 77
of the bottles. The method used was to wipe the bottles and cork
stoppers with a damp towel and then remove the cork. The cork
puller which was used grasps the neck of the bottle in such a way as to
cover the opening and remove the cork without the inrush of air that
occurs when the ordinary corkscrew is used. A flame was then passed
over the mouth of the bottle, after which the upper layer of ketchup
was poured out, so as to discard any material which might have been
contaminated in handling. Tomato gelatin was used as a medium and
cultures were made in petri dishes.
There were 17 plates on which no organisms developed, indicating
that the ketchup was sterile. Of the 60 plates having organisms, 54
had molds, 22 of these having molds alone; 21 plates had yeast-like
organisms, 3 plates having these only; 29 plates had bacteria, 4 having
bacteria alone. Sometimes a plate would have only one form of
organism, but more often there was a mixture present. Of 15 plates
having only one form of organism, 3 had yeast alone, 2 bacteria alone,
and 10 had mold alone. Of the 77 bottles of ketchup from which the
inoculations were made, 41 were without and 36 with preservative, and
of the 17 sterile ketchups, 8 contained sodium benzoate and 9 were
without preservative.
A considerable part of the experimental ketchup proved not
to be sterile. The organisms present were of the class which
require oxygen for their growth and therefore they had only been
arrested in their activity. No growth could take place so long as
22 EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP.
the air was excluded and therefore no spoilage could occur. When
the cork was drawn, the organisms could grow and cause spoilage,
and this is a much more potent factor than the entrance of germs
from without. Bottling and sealing the ketchup quickly while
hot so completely excludes the air that only a few colonies of
yeast or mold may be found on subsequent microscopical exami-
nation. Filling at a low temperature and corking while cool
allows sufficient air to remain incorporated in the ketchup and
neck of the bottle to permit a considerable growth of the organisms
and a product derived from good stock may thus acquire the
appearance of ketchup derived from partially decayed material.
A ketchup in which bubbles of air are incorporated in filling may
show a growth of mold at each bubble throughout the mass.
The foregoing statements apply to ketchup containing sodium
benzoate as well as to the non-preservative goods of the character
used in these experiments.
EXPERIMENTS WITH PRESERVATIVES.
SODIUM BENZOATE.
The preservative in general use in ketchup is sodium benzoate.
Salicylic acid is used, but only to a limited extent. The amount of
sodium benzoate used, according to the labels, varies from one-
sixteenth to one- tenth of 1 per cent; but on some labels the amount
is not stated. Experiments were made to determine the amount
necessary to check the spoilage of ketchup.
Two organisms, a mold and a yeast, were selected on which to make
the tests. The mold was the ordinary blue mold, Penicillium, which
was present in many of the brands of ketchup and is found commonly
on acid foods. It was selected on account of its prevalence and
resistive power. The yeast was obtained from ketchup and was also
a vigorous grower, forming a thick, wrinkled film on various media.
Any effect on the growth of the yeast could be seen readily in its
manner of forming the film.
Portions of tomato gelatin to which 0.1, 0.5, 1, and 2 per cent, re-
spectively, of sodium benzoate were added, were first inoculated with
the mold. There was no development in those containing 1 and 2
per cent; a retarded development resulted in that containing 0.5 per
cent, and the growth when 0.1 per cent was used was nearly normal,
showing very little difference from that in the gelatin without sodium
benzoate.
Ketchup was next tried as a medium, but the amount of benzoate
was reduced to one-sixteenth, one-twelfth, and one-tenth of 1 per cent,
as it was thought that some of the other constituents of the ketchup
were antiseptic to a slight degree. The growth in the ketchup was
EXPERIMENTS WITH PRESERVATIVES. 23
irregular, though the benzoate checked development in all. Equal
amounts of benzoate were used in tomato bouillon, with practically
the same results as in the ketchup. The development was checked
in all, and in some plates one-sixteenth of 1 per cent seemed to be
fully as efficacious as one-tenth of 1 per cent. When the mold was
examined under the microscope, the filaments were found to be much
swollen and distorted in shape, and filled with a coarsely granular
protoplasm, containing much fat, as indicated by the blackening with
osmic acid. The culture containing the mold which gave the least
development seemed to show the least distortion and swelling of the
filaments.
The results indicated that in using sodium benzoate. as a preserva-
tive there is uncertainty as to results, even when using the maximum
amount allowed — one-tenth of 1 per cent. They also indicated that
this preservative had an injurious effect on the living matter of the
mold. (See PI. II; compare with normal growth, PL I.)
SALT.
The effect of salt in checking development was tested by using
tomato bouillon as a medium and adding 5, 10, 15, 20, 25, and 30
grams of salt, respectively, to 100 cc. These were inoculated with the
mold. The 5-gram solution seemed to have no effect on development.
When 10 grams were used growth appeared as soon as in the bouillon
without salt, but was not so extensive. In the 15-gram solution
growth was retarded four days, and most of that which did develop
remained submerged, the mold growing normally on the surface.
With 20 grams the growth was five days slower than the normal in
starting, and after that there was only a slight development. In the
25-gram solution, the growth started at the same time as when 20
grams were employed, but remained stationary, while with the 30-
gram solution, no development occurred.
The yeast was checked slightly by 5 grams, and very materially by
the 10-gram solution, as it required two days for a thin, delicate film
to form, whereas in ordinary solutions a rather thick film is formed
within twenty-four hours or even in less time. There Was no develop-
ment in the 15-gram solution.
SUGAR.
The effect of sugar was tested on both the mold and the yeast by
adding it to tomato bouillon. It was supposed that a low percentage
of sugar like the salt would plasmolyze the cells, and in this way check
growth, but it seemed to have no effect until the amount was increased
to 25 grams per 100 cc of bouillon. In this solution growth appeared
as soon as with the weaker solutions, but there was a smaller amount.
In the 25 to 40 gram solutions there was less development as the
24 EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP.
amount of sugar increased. In the 70 and 75 gram solutions growth
was delayed one day in its appearance. In the 80, 85,. and 90 gram
solutions growth was delayed two days, the colonies growing sub-
merged at first, but after a time forming on, the surface. The myce-
lium remained very thin, but a thick layer of spores formed. From
this point on the amounts were increased by 10 grams up to 200. The
development became slower and less successively until 170 grams
were added. In this case a small colony appeared on the surface in
seven days, but seemed to grow less after that. The solutions were
held, and in time crystals separated from the thick sirups. After two
months dry-looking colonies developed along the edges, forming a
ring, and some formed on the surface, these occurring also in the
flasks containing 170, 180, 190, and 200 grams of sugar per 100 cc.
The colonies were a dull greenish drab in spots, the remainder being
white.
For the yeast the 80-gram solution of sugar was the strongest in
which any development took place.
SPICES.
Experiments to determine the value of the spices as antiseptics
were made, using water infusions, acetic-acid extracts, and oil
extracts.
WATER INFUSIONS.
In making the water infusions 20 grams of the whole spices, with
200 cc of water, were boiled for forty-five minutes. This is approxi-
mately the length of time that the spices are cooked in the ketchup in
the factory. The liquid was then filtered and from 0.1 to 5 cc of the
filtrate was used in 10 cc of tomato bouillon. The same organisms
were used as in the former experiments.
The tests showed that cinnamon and cloves were the strongest anti-
septically. These checked growth when used in small amounts, but
it required 3 cc of the cinnamon and 1 cc of the cloves to inhibit the
growth of the mold. Mustard, paprika, and cayenne pepper checked
growth also, but 5 cc, the highest strength used, did not inhibit
growth. The ginger, mace, and black pepper had no apparent effect
in the quantities used.
The effect of the spices on the development of the yeast was some-
what different from their effect on Penicillium. The cinnamon
showed the strongest action, 3 cc being effective, whereas 5 cc of the
cloves was required. The cayenne pepper came next in effective-
ness, and after that the black pepper. The ginger, mace, and mus-
tard solutions had no effect in the strengths used.
The remainder of the spice infusions were kept in glass-stoppered
bottles in the laboratory, and in a few weeks' time there was a coat-
ing of mold formed over the surface of the mace, the mustard, and
'iveasiTY
EXPERIMENTS WITH PRESERVATIVES., of 2i
the black and cayenne peppers. The paprika had small, stunted col-
onies dotting the surface.
At the time that these experiments were made a quantity of the
ground spices were placed in large petri dishes and water was added
to make a heavy paste. One set of these was inoculated with the
mold, and another set with the yeast, and all were kept in a warm
place. No development of either organism appeared on the cinna-
mon, cloves, or mustard; on the others a growth first showed in three
days. On a normal medium growth appears in twenty-four hours.
On the mace, paprika, and cayenne pepper the Penicillium and yeast
with which the pastes were inoculated were overgrown in a few days
with black mold (Rhizopus nigricans) .
ACETIC-ACID EXTRACTS.
In the manufacture of ketchup acetic-acid extracts of the spices
are sometimes used instead of the whole spices, on account of their
supposed antiseptic properties as well as their greater strength and
convenience in handling. One minim of the standard acetic-acid
extracts is equal in strength to 1 grain of the whole spices. The acid
extracts obtained included allspice, celery, cloves, coriander, garlic,
and black pepper.
In the tests 0.1, 0.2, 0.3, 0.4, 0.5, and 1 cc, respectively, of the
extract was added to 10 cc of tomato bouillon. One set was inocu-
lated with the mold and another set with the yeast. In the case of the
mold, no growth occurred with the allspice and cloves; the celery
checked the growth materially, there being no indication of mold
until the sixth day. Normally a fairly strong growth occurs in
twenty-four hours. In the solution containing 0.3 cc there was only
one small colony in thirteen days, and no further development. In
the solution containing the coriander, the growth in the 0.5 cc solu-
tion did not appear for three days, the 1 cc solution showing no
growth. The garlic had practically the same effect as the coriander,
while the black pepper was stronger, no growth appearing in the solu-
tion containing 0.5 cc.
The yeast was slightly stronger in resisting the effect of the extracts.
No growth appeared with the allspice and cloves; 0.5 cc of the celery
and 1 cc of the coriander were required to inhibit growth, and the
garlic and black pepper gave similar results, a weak development
occurring in the solutions containing 1 cc.
OIL EXTRACTS.
Oil extracts of the spices were tested in the same manner as the
water infusions and the acetic-acid extracts. The oils were so strong
that in order to handle them easily they were mixed with equal vol-
umes of alcohol, except that the mace, which was in the form of a
26 EXPEKIMENTS ON THE SPOILAGE OF TOMATO KETCHUP.
paste, was mixed with two-thirds its volume of alcohol. To 10 cc of
tomato bouillon were added 0.1, 0.2, 0.3, 0.4, and 0.5 cc, respectively,
of the oils of cinnamon, cloves, mace, mustard, and black pepper.
In the case of the mold, there was no development in the solutions
containing cinnamon, cloves, and mustard; in those containing mace
and black pepper the development was slower than the normal, that
in the black pepper being more pronounced. On the yeast the effect
was similar, no development occurring in the cinnamon, cloves, and
mustard, and a retarded development taking place in the mace and
black pepper, that in the black pepper being the more pronounced.
The experiments show that some of the spices, notably allspice,
cinnamon, and cloves have decided antiseptic value, but that the
peppers are not as valuable as is generally supposed.
The oil extracts have been advocated for use in ketchup instead of
the whole spices, but in quantities which would be useful antiseptic-
ally their use would be objectionable, for when present in approx-
imately the same proportions as are the whole-spice infusions, the
flavor is too strong and masks the more delicate flavor of the tomato.
The acetic-acid extracts are more effective than are the water infu-
sions, and they are not objectionable in the ketchup.
VINEGAR AND ACETIC ACID.
An experiment was made to determine the antiseptic value of
vinegar and acetic acid. Commercial 50-grain distilled vinegar
was used. It was found that when 30 per cent of this vinegar was
added to the tomato bouillon the development of mold was checked
and the extent to which it was checked increased with the increased
amounts of vinegar. The development in the solution containing 30
per cent of the vinegar was two days later than the normal in
starting, while the solution containing 100 per cent was eleven
days delayed and showed but little growth.
An 80 per cent solution of glacial acetic acid was used. One-half
of 1 per cent added to the tomato bouillon checked growth to the
same extent as. 30 per cent of vinegar, and no development occurred
when the quantity was increased to 2 per cent.
Experiments were then made in which vinegar was added to
the ketchup in proportions varying from 1 part in 32 to 1 part in
8, with the result of greatly delaying the appearance of the mold
as the proportion increased. With the increase in vinegar it was
necessary to add sugar and slightly more spices to overcome
the pungency of the acid and thus insure good flavor. The addi-
tion of the vinegar to the pulp had the effect of arresting the
action of the oxidase and thus the bright color was maintained.
The usual custom in factory practice is to add the vinegar near
the close of the cooking process otherwise a considerable portion
EXPERIMENTS WITH PRESERVATIVES. 27
of the acid will be driven off. This practice was followed in the
experimental work, but it has since been found that continued
heating in the presence of the acid has some effect upon steriliza-
tion, and therefore the increased amount of vinegar is effective not
only because of the additional acid present, but also because the
heating in the after process is thereby rendered more efficacious.
This line of experiments gives promise of practical results in
producing a ketchup which will not only keep while in the bottle,
but will also keep longer after it is opened. Each manufacturer
must work out the quantities that could be used with his formula
and still retain the character of his goods.
OIL.
In ketchup manufacturing it is customary, if an agitator is not
used, to put a small amount of fat in the kettle to check the ebul-
lition during the reduction of the pulp. The amount used in this
manner is not sufficient, however, to be apparent in the ketchup.
Brannta states that in some factories, where the trimmings are
allowed to accumulate for the season, they are given liberal doses
of oils and condiments when cooked, in order to disguise their defects,
so that the product can be placed on the market as " fresh tomato
catchup." That the use of oils is increasing is evident from the
comparison of the ketchup of the past season with that of former
years.
When oil is used in ketchup, it is easily detected under the micro-
scope, as it appears in the form of shining, yellow globules which
blacken gradually when treated with osmic acid. Besides this,
the oil comes to the surface of the ketchup, where it can be seen
readily, and if considerable oil has been used a distinct layer is
formed. When the ketchup has been made for some time, the oil
changes so that the ketchup has a peculiar "greasy" odor, or the oil
may be so changed as to give a decidedly rancid smell to the ketchup.
Oil usually causes a deterioration in flavor and odor, though some
of the ketchups to which it has been added do not spoil readily.
Olive oil, cottonseed oil, and oleomargarine are used. That the oil
is not considered one of the regular known ingredients of the ketchup
is shown by the failure to declare its presence on the label.
To test the antiseptic value of oils in ketchup, experiments were
made, using olive oil, cottonseed oil, and oleomargarine in the pro-
portions of 1 part of oil to 1,000, 750, and 500 parts of ketchup,
respectively. The ketchup was made in small quantities, 2 gallons
for each experiment. After bottling, all except the check bottles
were inoculated with Penicillium and kept at kitchen temperature.
All spoiled, and neither the quantity nor kind of oil used had any
"Brannt, W. L., A Practical Treatise on the Manufacture of Vinegar, 1900, p. 455.
28 EXPERIMENTS ON THE SPOILAGE OP TOMATO KETCHUP.
marked effect in preventing spoilage. That the oils affected the
development of the mold was evident. The mold developed first
at the junction of the ketchup with the bottle forming a ring which
spread gradually over the surface developing a somewhat heavy
mycelium. This remained white longer than usual, spores forming
very gradually, as indicated by the change in color from white to a
delicate blue. At the end of three weeks only spots of color appeared
on the surface and these were still blue, though in ordinary develop-
ment the blue color changes to green in two or three days.
Another test was made, using olive oil only, and in the proportions
of 1 part of oil to 500, 400, and 300 parts, respectively, of the ketchup.
Reduction was made in a steam-jacketed kettle, the oil being added
when the ebullition of the ketchup was the strongest, after which
the boiling was continued for fifteen minutes. The ketchup was
bottled, unsterilized bottles being used, then covered loosely with
the metal caps.
The time required for the ketchup to spoil was longer than in the
first set, but there was not sufficient difference nor enough uniformity
in the time to indicate that the use of oil in ketchup is desirable, eveii
if the change of flavor and odor be not taken into consideration. Th<§
average number of days before spoilage for those containing 1 part oj
oil to 500 parts of ketchup, was thirteen and two-thirds days ; one has
has not yet spoiled (a period of forty-five days), while the first bottle
spoiled in four days. Those having 1 part of oil to 400 parts of ketchup
had an average life of nine and three-fourths days, the minimum being
three days, and the maximum twenty-six days. Those having 1 part
to 300 parts of ketchup on an average did not spoil for six and three-
fourths days, the minimum being four days, and the maximum
eleven days.
The failure of some of the bottles to spoil, though similar in every
known respect to those which did spoil, is a feature peculiar to ketchup
and is familiar to manufacturers who make careful tests before putting
their product on the market. For this reason a rather large number
of bottles should be used in a test in order that the results may be
approximately accurate and represent general conditions.
STUDY OF PENICILLIUM IN KETCHUP.
PeniciUium is a plant which is distributed widely and apparently
is able to grow wherever organic matter is found, though flourishing
best when the material contains acid. It causes loss in canneries,
breweries, distilleries, etc., the only use made of it being in the manu-
facture of Roquefort cheese, the immature cheese being inoculated
with the conidia for the effect the mold produces in the maturing
process.
Bui. 1 19, Bureau of Chemistry, U. S. Dept. of Agriculture.
Plate I.
F.g. 1— Conidia, Normal Size and in Various Stages of Germi-
nation, Some with Branching Hyph/e (X 325).
Fig. 2.— Conidiophore, Showing Unusually Large Development
of Conidia, from Culture in Moist Chamber (X 325).
PENICILLIUM.
£PJ?N •
Bui. 1 19, Bureau of Chemistry, U. S. Dept. of Agriculture.
Plate II.
Fig. 1.— Conidia and Hyph/e from Culture in Experimental
Ketchup Containing One-sixteenth of One Per Cent of
Sodium Benzoate (X 325).
Fig. 2— Conidia and Hyph>e from Cultures in Experimental
Ketchup Containing One-tenth of One Per Cent of Sodium
Benzoate (X 325).
CULTURES FROM KETCHUP PRESERVED WITH SODIUM
BENZOATE.
V ** OF THE
" UNIVERSIT
OF
^LIFORNJ.!
STUDY OF PENICILLIUM IN KETCHUP. 29
DEVELOPMENT.
In developing, the mold forms a white felt-like mass, covering the
medium on which it is growing; then as development proceeds, it
changes to bluish-green, and finally to a darker, duller color. The
change in color is accompanied by a change in structure, the surface
becoming powdery in appearance, a slight current of air being suffi-
cient to dislodge a cloud of fine dust. This fine dust is formed of
small, spherical bodies, the spores or conidia (from the Greek meaning
dust). These need no resting period, but are able to develop at once.
When the conidia lodge on a moist substance they swell to a much
greater size and then send out a tube from some part of their surface.
The tube lengthens and septa form, dividing the tube into sections,
or cells. At the same time branches are sent out, which again form
other branches. The original conidium sends out a second branch
shortly after the first one, and usually from the opposite side, and
may even send out a third one. The formation of the septa and the
subbranching goes on in all, so that in a short time the branches mat
together and form a felt-like cover.
REPRODUCTION.
After a shorter or longer period of development, dependent on the
conditions, branches are sent perpendicularly from the substratum,
and into the air. These branches cease their growth in length, sending
out branches near the tip, which take the same general direction as
the original branch. Each of these subbranches is called a sterigma
(from the Greek word meaning support). In vigorous development
the sterigmata may form secondary branches, the whole forming a
tassel-like arrangement. The tip of a sterigma enlarges, a septum
forms around the enlargement, cutting it off from the sterigma, and
forming a conidium. The sterigma develops to the original length
and another conidium is formed, the operation being repeated many
times, thus forming a chain of spores. As the other sterigmata are
also forming conidia in the same manner, a series of these chains is
formed close together. After the cessation of conidial development,
the filament below the sterigmata is disorganized, setting free the
conidia. The filament and head together are called the conidiophore
(Greek, dust-bearer).
Penicillium forms spores sexually, but the conditions for their for-
mation are unknown. Brefeld obtained them by growing the mold
on damp bread placed between two glass plates, and excluding the
air. Lindner obtained carpospores on a wort gelatin culture in a
petri dish, from which the air was excluded. The writer has tried
various methods for obtaining carpospores, but so far without success.
Moist chambers were used with various media, excluding the air.
30 EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP.
The development of the mold is seemingly dependent on the
amount of air in the chamber at the time of sealing. After the air is
exhausted, the conidiophores assume fantastic forms, developing only
one or a few sterigmata, and on these one or few conidia. In other
cases the conidiophores are fascicled, in no cases, however, forming the
conidia as luxuriantly as when air is supplied. The hyphse become
clear, much vacuolated, and develop more septa, and some of the
cells become much enlarged. An enlarged cell will often contain two
or three septa, thus forming cells that are not larger than disks. In
cultures from which the air was excluded from the start, no develop-
ment took place. In test-tube cultures sealed with paraffin after
twenty-four hours, the mold developed on the surface of the gelatin,
forming a felted white mass, but no conidia nor carpospores were
formed.
GROWTH IN KETCHUP.
The form of Penicillium which was used in the experiments was
isolated from ketchup in which it grew luxuriantly. When conidia
are first formed on the ketchup, they are a delicate blue in color; they
then become bluish green, then green, and finally olive. The develop-
ment of the color of mold growing on ketchup is practically the same
as when grown in wort, tomato bouillon, pea bouillon, or gelatin
made with these solutions as a basis. In ketchup containing sodium
benzoate, the blue color appearing first remains for a long time, and
in old cultures the mold is a dull drab, not olive, as in normal develop-
ment.
In ordinary ketchup made without a preservative, the mold forms
a heavy, wrinkled mycelium, showing a large development of conidia.
In the bottles of ketchup, the mold pushes down into the ketchup,
becoming entirely submerged, a clear liquid covering the mold and
separating it from the ketchup. This occurred in more than one hun-
dred bottles. No secondary mycelium formed on the surface of the
liquid, a method of development which frequently occurs in ordinary
media when a mass of mold is submerged.
An exception to this was shown in ketchup which had developed
the mold in the laboratory. The bottles were then put in the refriger-
ator for two weeks. During this time scarcely any development took
place ; but after they were again placed in the laboratory, the myce-
lium pushed down into the ketchup and a new, very thin mycelium
developed on the surface. The filaments when seen under the
microscope were swollen, had irregular outlines, and a comparatively
smaller number of septa, and were filled with a coarsely granular pro-
toplasm. The ends were blunt and misshapen and the sterigmata
were irregular, tending more .toward a fasciculated arrangement, and
forming fewer conidia. The filaments from the vinegar and acetic
STUDY OF PENICILLIUM IN KETCHUP. 31
acid media had the same appearance as those developed on ketchup,
but had a smoother outline.
TEMPER ATTIRE TESTS.
The limits for the germination of Penicillium, as given by W. J.
Sykes,« are 2° to 43° C. (35° to 110° F.), and the most favorable
temperature 22° to 26° C. (72° to 79° F.). This author states also
that according to Pasteur the dry spores retained their vitality at
108° C. (226° F.), but that they were soon killed when immersed in
boiling water. Klocker6 quotes Pasteur as saying that the conidia
are killed if exposed to a temperature of 127° to 132° C. for half an
hour, but that they retain life at 119° to 121° C.
A series of tests was made to determine the thermal death point of
the moist and dry conidia of the Penicillium used in the experiments,
a young, vigorous development on ketchup being used. The flasks
were kept under observation for a month after the tests were made,
as in many cases a development does not occur in the usual time.
The high temperatures applied for longer periods of time were tried
first, but both temperature and time were reduced as results from the
series were obtained. Only the conditions obtaining in the final tests
are given in the table. It was found that the Penicillium used did
not have the high resistance supposed.
The tests were made in small flat-bottomed 10-cc flasks, tomato bouil-
lon being used for the tests on moist conidia. The bouillon was used
so as to have the conidia in a nutritive medium after the test was made,
without transferring. The time for those at 1 00° C. was estimated from
the time of ebullition. At the end of the specified time, the flasks were
cooled promptly under running water. As the flat bottoms gave com-
paratively large surface, the heating and the cooling could be effected
in a short time. For the tests below 1 00° C . a vessel of water was heated
to the desired temperature, and the flasks were immersed in it and
shaken constantly. The dry conidia were placed in test tubes which
were immersed in boiling water for the desired time and cooled under
running water, after which 10 cc of sterilized tomato bouillon was
added. After determining the death point in this manner and finding
it to be much lower than had been supposed, it was decided to make
the test again, but using ketchup as the medium. Ten grams of
ketchup were sterilized, then inoculated from a vigorous growth of
mold, and tested with a set in which the tomato bouillon was used.
For those below 100° C. the two flasks which were to receive the same
temperature were held in the vessel of water at the same time, so that
« Principles and Practice of Brewing, 1907, p. 284.
&Ibid., p. 281.
32
EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP.
as nearly as possible the treatment would be identical. The following
results were obtained :
Thermal death point of moist and dry conidia of Penicillium.
PENICILLIUM IN 10 CC OF TOMATO BOUILLON.
No. of
experi-
ment.
Temper-
ature.
Time of
heating.
Time be-
fore ger-
mination.
Period of observation and developments.
1
2
°C.
85
80
75
70
65
60
55
Minutes.
i
1
1
5
5
5
5
Days.
3
Dark strings from spores; 9 days; no development.
3
4
5
6
7
3
3
3
Dark strings running from spores; 9 days; growth normal,
spots on surface.
Do.
Do.
PENICILLIUM IN 10 CC OF KETCHUP.
100
3
100
2
100
100
1
I
Instant.
100
85
i
2
80
1
2
75
1
2
70
5
8
65
5
9
60
5
3
55
5
4
2
Colonies on sides; 8 days; surface covered, green.
Do.
Do.
Colony on surface.
Do.
Colonies on sides; 8 days; surface covered, green.
Do.
Ring around sides; 3 days; surface nearly covered.
DRY CONIDIA.
100
10
4
100
15
4
100
20
7
100
25
10
100
30
10
100
35
Rough appearance, like that in ketchup.
Do.
Slight growth.
Growth barely perceptible.
Do.
Conidia stained readily, showing they were
YEAST.
55
5
2
60
5
2
65
5
2
70
75
5
5
100
Instant.
Wrinkled film; liquid turbid.
Do.
Thin, smooth film; liquid clear.
The moist heat was very effective in destroying the vitality of the
conidia of Penicillium, the death point being 27° C. higher than
the maximum temperature for germination as given by Sykes.
The heating was more effective in destroying germs when applied to
bouillon than to ketchup, no development taking place for any tem-
perature above 65° C, even when applied for a short time.
In the ketchup the lower temperatures for the longer periods of
time were more effective in checking the development, even though
they did not destroy the vitality. In the ketchup, with the excep-
tion of Nos. 9 and 10, the colonies started invariably along the sides
of the flasks. The greater access of air to those on the sides would
HISTOLOGICAL STRUCTURE OF KETCHUP. 33
account for this. The conidia on the sides of flasks Nos. 9 and 10
must have been destroyed, as no -development took place in either
case except in the center of the surface.
The dry conidia were destroyed at 100° C. when heated for thirty-
five minutes; they did not reach a normal development in any case,
eVen when heated for only ten minutes, many of the conidia being
destroyed by this treatment. Where development failed to take
place, the conidia were stained with a water solution of eosin, so as
to be sure that the effect was death, and not an arrested development.
The results of the tests do not agree with those obtained in factory
practice, where the ketchup is cooked at 100° C. for at least forty
minutes and sometimes for fifty or fifty-five minutes, depending on
the consistency of the pulp.
HISTOLOGICAL STRUCTURE OF KETCHUP.
In ketchup are found parts of all the various tissues of the tomato
broken into fine pieces by the action of the cyclone. Although the
sieves take out the seeds, skins, and any large pieces, particles of the
various tissues are present in size sufficient for identification. Among
the distinctive features are the red crystalline bodies in the paren-
chyma, which serve to a certain extent to distinguish the paren-
chyma from that of other plants which might be used for adultera-
tion, and serve also to differentiate the natural from the artificially
colored ketchup. Some of the red dye used colors all protoplasm
indiscriminately, even that of the fungi present, and as a colored
ketchup is usually poor stuff, containing many fungi, the mold
filaments, yeast cells, and bacteria receive their share of the color.
Other red dye used is in the form of fine powder, which does not go
into solution, but is distributed as irregular particles which are dis-
tinct from the red crystalline bodies.
Good ketchup made from whole tomatoes has a clean appear-
ance readily distinguishable under the microscope; but the poor
ketchup has usually a superabundance of fungi present, fully devel-
oped colonies of mold, many forms of conidia, besides yeast-like
cells, and different forms of bacteria. All of these may be dead,
but neither preservatives nor dosage of odorous spices can disguise
their presence. In some of the ketchup examined, which was put
up in attractive form and labeled as being made from the whole
tomatoes, and which had the appearance and odor of good ketchup,
the microscope showed the presence of such quantities of fungi as
to leave no doubt that the tomatoes were spoiled when cooked.
It is presumable that some of the dealers placing this sort of
stuff on the market do not know its condition themselves, and
either buy their pulp from other factories or trust its manufacture
34 EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP.
to employees whose only care is that the ketchup shall have a
bright color and shall "keep." Some of the mould filaments and
conidia are distorted in the same way as those of the Penicillium are
when grown in ketchup to which sodium benzoate has been added.
The ketchup made from sound tomatoes and manufactured in a
cleanly manner has practically no fungi present. The ketchup that
was used in these experiments was made at different times during
the season and was of this character, no bottle examined showing
mold filaments when first opened.
MICROSCOPIC EXAMINATION OF SOME COMMERCIAL BRANDS.
In examining ketchup the color, odor, amount of discoloration,
presence of foreign tissue, foreign coloring matter, oil, and fungi
were determined. If no preservative was mentioned, some of the
ketchup was put in petri dishes and inoculated with Penicillium to
determine whether growth could take place. The following examina-
tions are reported, as they represent some of the best known brands
on the market:
No. 9. — Opened September 2, 1907; age unknown; pint bottle; no preservative
mentioned; not spoiled July 6 of following year. This ketchup was guaranteed to be
made from fresh, ripe, tomatoes by a new process. The color is an unnatural red, has
not faded, and the odor is good. The microscope showed the presence of much refuse,
and large quantities of fungi, whole colonies of molds, the filaments distorted, many
yeast cells, and bacteria. The red color was not confined to the red crystalline bodies,
as is the case in ripe tomatoes, but the whole of the protoplasm of the cells, including
the nucleus and nucleolus was red, as were also most of the mold filaments and yeast,
indicating the presence of considerable artificial coloring matter. The structure
indicated that the stock had been manufactured from "trimmings," and further,
that they were not fresh when used, but had fermented. There was no oil present.
The "new process" is a success in keeping ketchup, as no preservative is mentioned.
The price was 20 cents.
No. 112. — Another bottle of the same brand of ketchup; examined in April, 1908;
presumably manufactured in 1907; one-twelfth of 1 per cent of sodium benzoate
declared on label; a bright red; guaranteed to be from fresh ripe tomatoes and uncol"
ored. The microscope showed no dyeing of the tissues, few fungi, and no extraneous
matter. The price was 20 cents.
No. 17. — Opened September 28, 1907; age unknown; a pint bottle; sodium ben-
zoate declared on supplemental label, no amount being stated; reddish brown color,
badly discolored on top; greasy odor; not spoiled July 6, 1908; refuse present; large
amount of oil; many fungi; the mold filaments enlarged and distorted. The price
was 15 cents.
No. 109.— Another bottle of the same brand examined in April, 1908; presumably
manufactured the preceding year; had one-tenth of 1 per cent of sodium benzoate;
not spoiled July 6, 1908; reddish brown color, discolored near top; greasy odor.
This was practically the same as the first bottle examined, had fewer mold filaments,
but many bacteria.
No. 18.— Opened September 28, 1907; age unknown; pint bottle; no preservative
mentioned; not spoiled July 6, 1908. A neck label stated that it is made from sound
SUMMARY. 35
ripe tomatoes and uncolored. Color reddish brown; greasy odor; many oil globules;
too many mold filaments and bacteria for sound tomatoes. Price 20 cents.
No. 113. — Another bottle of the same brand examined in April, 1908; said to have
been manufactured in 1908; no preservative mentioned; not spoiled after standing
open for seventy days; same as No. 18 in color and odor; oil and many fungi again
present.
No. 10. — Opened September 2, 1907; age unknown; half -pint bottle; no preservative
mentioned; not spoiled July 6, 1908. A neck label 2 inches in height guaranteed
the highest quality; an extra label lower down on the neck stated the product to be
the natural color, and made from fresh, ripe tomatoes; the regular label carried the
brand, manufacturer's name, etc. Color brown; sweetish odor; colonies of mold;
distorted filaments; many bacteria; a few small oil globules. Price 25 cents.
No. 106. — Same brand; pint bottle; examined in April, 1908; said to be manu-
factured in 1907; color red, discolored near surface; 2-inch neck label in addition to
regular label ; no preservative mentioned; did not spoil in seventy days; oil globules;
particles of red, amorphous matter; whole colonies of mold, as well as fragments of
filaments; teeming with bacteria.
No. 77. — Different brand, but same manufacturer as Nos. 10 and 106; age unknown;
pint bottle; one-twelfth of 1 per cent of sodium benzoate declared; opened December 1;
placed in incubator at 95° F. for a month; not spoiled July 6; color reddish brown;
greasy odor; oil globules, many mold filaments, and bacteria present. Price 20
cents.
No. 107. — Third brand from same manufacturer as preceding; said to be manu-
factured in 1907 ; half -pint bottle; one-twelfth of 1 per cent of benzoate of soda declared;
layer of oil on surface; sweet odor; reddish-brown color. Oil globules prominent
feature microscopically, whole colonies of distorted mold were present, and sample
contained many different forms of bacteria. Price 10 cents.
No. 14. — Opened September 2, 1907; age unknown; no preservative mentioned; not
spoiled July 6, 1908; half -pint bottle; color red; good odor; few bacteria; free from
refuse. Price 25 cents.
No. 108. — Same brand as No. 14; said to be manufactured in 1907; pint bottle;
one-tenth of 1 per cent of benzoate of soda declared; color red; good odor; few fungi;
clean and free from refuse.
No. 33.— Opened October 24, 1907; age unknown; one-tenth of 1 per cent of ben-
zoate of soda declared; spoiled November 1; pint bottle (14 ounces); sweetish odor;
brown color; many molds, yeast and bacteria. Price 10 cents.
No. 114- — Same brand as No. 33; said to be manufactured in 1907; opened in April;
not spoiled in seventy days; many molds, yeasts, and bacteria; some green tissue, and
filaments of algae. The price was 10 cents.
SUMMARY.
1. The experiments made during the season of 1907 on the manu-
facture of tomato ketchup without chemical preservatives were con-
ducted under factory conditions and upon a commercial scale. The
results prove that such a ketchup can be made and delivered to the
consumer in perfect condition ; the product in question having already
stood ten months, unopened, without showing the slightest indication
of spoilage.
2. The product is of excellent consistency, flavor, and color. The
formula employed regularly in the factory where the experiment was
36 EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP.
conducted was used, but other recipes could be adapted without
changing the character of special brands. In the manufacture of
such a product the following precautions were observed:
(a) Whole, sound, ripe tomatoes and high-grade salt, sugar, vinegar,
and spices were used ; care and cleanliness were observed at every step
of the preparation, and the preservation accomplished by heat in the
following manner: The pulp was cooked in a steam kettle for about
forty minutes, until the mass was reduced to about one-half its vol-
ume. Additional processing after bottling did not appear to be
necessary to keep the ketchup before opening, and had no effect in
these experiments in delaying spoilage after opening.
(b) Ketchup was bottled directly from the cooker at a temperature
of 205° F. in bottles prepared in two ways: (1) Sterilized in a steam
chamber at 230° F; (2) Washed in hot water, rinsed, and heated to
190° F. in a dry heat for at least thirty minutes. Ketchup was also
bottled after the usual process of sieving at 165° F. in bottles prepared in
a similar manner. The corks for all bottles were sterilized in a paraffin
bath at 270° F. The same ketchup which was bottled at 165° F. was
also given subsequent processing at 190° F. and 212° F. for twenty
and forty minutes. All have kept without spoilage.
3. Some of the condiments have a limited antiseptic value, but can
not be depended upon to prevent spoilage in the quantities used for
flavoring. While sugar and vinegar can be added in such amounts as
to delay the appearance of molds, and cinnamon and cloves can be
depended upon to check deterioration to some extent, these condi-
mental substances have only an incidental value for this purpose.
4. The spoilage of ketchup after opening depends more upon the
temperature of the place in which it is kept than on any variation in
the manner of processing. Fresh ketchup held, after opening, at a
temperature of 95° F. kept for ^ve days on an average without any
trace of mold appearing; at 72° it kept for six days; at 67° for eight
days ; about 46° (refrigerator) , fourteen days ; and at from 30° to 60°
for twenty-seven days. These figures represent the time at which the
first trace of spoilage occurred in the neck of the bottle — had this been
removed the figures would be much increased — and by no means
represent the maximum time during which the ketchup could have
been used, the maximum figures, even under these conditions of obser-
vation, varying from eight to fifty-eight days. The keeping of the
ketchup in warm storage at 70° for one hundred and fifty days before
opening hastened the average time of spoilage after opening about
one day. The advisability of using small containers, to get the best
results with a first-class ketchup, is apparent.
5. Sodium benzoate, even when used in the proportion of 0.1 per
cent, is not always effective, and has an injurious effect upon the
SUMMARY. 37
living matter of the molds, shown by the distortion and swelling of the
filaments, which are filled with a coarse granular protoplasm contain-
ing much fat.
6. Artificially colored ketchup can be detected under the micro-
scope by the fact that certain tissues, normally colorless, are dyed red,
or by the presence of fine, red, amorphous particles which do not go
into solution.
7. Ketchup made from whole ripe stock in a cleanly manner gives
a clean appearance under the microscope, but few molds, yeasts, and
bacteria being present. On the other hand, ketchup made from
trimming stock, or from tomatoes that have been allowed to spoil, con-
tains immense quantities of these growing organisms which may be
killed in the process of manufacture, but still give proof of the char-
acter of the material used. Ketchup as ordinarily made from trim-
ming stock should, therefore, be designated, so as to differentiate it
from that made from sound fresh tomatoes, as the two products are
radically different. This exactness in labeling is due no less to the
manufacturer than to the consumer, as it is impossible to make the
superior product in fair competition with the inferior one, other condi-
tions being equal, unless the two are properly designated, there being
naturally some difference in the price.
or THE
UNIVERSITY
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I
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