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S. 31. Tobacco—11.
Ws JP 128 Tak
U.S DEPARTMENT OF AGRICULTURE,
Report No. (His
PHYSIOLOGICAL STUDIES
OF
CONNECTICUT LEAF TOBACCO.
OSCAR LOEW,
OF THE DIVISION OF VEGETABLE PHYSIOLOGY AND PATHOLOGY,
DETAILED TO THE DIVISION OF SOILS.
A
>
=
WASHINGTON:
“GOVERNMENT PRINTING OFFICE.
1900.
PEATE Ol WANS EEA:
U.S. DEPARTMENT OF AGRICULTURE,
DIVISION OF SOILS,
Washington, D. C., March 24, 1900.
Sir: I have the honor to transmit herewith a manuscript concerning
some physiological studies of Connecticut leaf tobacco by Dr. Oscar
Loew, of the Division of Vegetable Physiology and Pathology. These
investigations are in continuation of the cooperative work between
this Division and the Division of Vegetable Physiology and Pathology
in carrying out in the broadest sense the tobacco investigations author-
ized by Congress and in the critical and exhaustive study of the possi-
bilities of the soils of the Connecticut Valley.
Respectfully,
MILTON WHITNEY,
Chief of Division.
Hon. JAMES WILSON,
Secretary of Agriculture.
LETTER OF SUBMITTAL.
U.S. DEPARTMENT OF AGRICULTURE,
DIVISION OF VEGETABLE PHYSIOLOGY AND PATHOLOGY,
Washington, D. C., March 20, 1900.
Ste: In accordance with a plan of cooperative work between this
Division and the Division of Soils, I respectfully submit herewith the
manuscript of a report on some physiological investigations of Con-
necticut leaf tobacco, by Dr. Oscar Loew. The work deals with a
number of questions relating to the physiology of the leaf and the
changes which take place during the processes of curing and sweating.
Respectfully,
B. T. GALLOWAY,
Chief of Division.
Prof. MILTON WHITNEY,
Chief, Division of Soils,
In Charge of Tobacco Investigations.
CONE NS:
Generaliphysiolocy of the tobacco plant) 322 2-59.22. 2522. ne ee ee er
iver fachors:otdevelopimMentiea ae ioe a ako m ye Brera thers aus ceed pene een
Remarks on the contents of the tobacco leaf .....-..--...-../-.---------
Acid content in different parts of the tobacco plant......-...---.--------
ipenine: of thestobaccor leak ees si rcena a yo Scarce ch se wee ne IS, Colk aes
Baaymolocy ot the tobacco: plant akeencee This fact seems to be in contradiction to the behavior of the plants in the seed
beds. A satisfactory explanation is wanting.
27
later development of the disease is shown by the following observation
of Mr. Du Bon: “It happened once that in a portion of a field every
other plant was a calico plant and the alternating ones were healthy
plants. This remarkable circumstance found its explanation in the fact
that in the process of machine planting two baskets were used contain-
ing the plants of two different seed beds, one bed being in a condition
to favor the disease, the other containing new soil. Two planters
worked here at the same time. The neglect of proper precaution in
taking the young plants from the seed bed may create a tendency to the
disease.” In this connection Mr. Barnes, of Hatfield, Mass., related
the following: ‘Young plants were taken from the same seed bed by
two different farmers, and, although the soil of the fields was the same,
one farmer had many calico plants in his field and the other had almost
none. Inquiry revealed the fact that one farmer took the plants from
the seed bed when it was quite dry, the other when it was well
moistened. In taking the plants from a dry bed one can not help lacer-
ating the roots, while from a well-moistened bed the roots may be
withdrawn in an almost intact condition. Lacerated roots do not
generally develop again to such a vigorous state as is required by the
quickly growing tobacco plants.”
For the prevention or diminution of the disease, Mr. Du Bon recom-
mends keeping the plants in the seed bed not too warm and also chang-
ing the seed bed. Beds that produce the disease might be grown over
for one year with grass, in order to put them in proper condition for
the production of healthy tobacco plants. While many planters seem
convinced that the diseased plants can not recover, others claim that
by hoeing and stirring the soil well the disease may be cured in the
initial stage. Mr. Barnes, of Hatfield, Mass., claims to cure the disease
by lifting the whole plant a little from the ground. In both cases a
better aeration of the soi] is reached. The writer is not prepared to
confirm or contradict these statements.
OBSERVATIONS ON CURING.!
INTRODUCTION.
The curing period is a time of continuous anxiety for the tobacco
planter. Too dry weather stops all changes in the leaves, particularly
the development of the proper color, while too moist weather, especially
at a temperature above 24° ©. (75° F.), favors the disastrous pole
burn. The great desire of the tobacco planter to become entirely inde-
pendent of the weather by such improvements in the barn construction
as will permit the proper regulation of the temperature and moisture is
therefore reasonable.
The general introduction of an ideal tobacco barn can be only a ques-
tion of time. If the tobacco is becoming too dry, steam should be
turned into the building; and if it is becoming too moist, dry heat
1These observations were made with leaf cured on the stalk.
.
28
should be applied. An agricultural journal describes such a barn as
follows:
‘
The barn is what is called a ‘‘three-bent” shed. There are three rows of beams,
one through the center and one on either side. A 2-inch steam pipe follows the out-
side beams around the shed. - This is believed to be sufficient to supply the neces-
sary heat to the whole building. The tobacco in the extreme outside of the shed
rarely suffers from the pole sweat. The tobacco through the center, and especially
that low down, is always the. worst affected, and the pipes are arranged to throw the
most heat into that part of the building. Ifthe experiment proves a success in pre-
venting pole sweat, the time is soon coming when artificial heat will be used entirely
in curing tobacco, for the even temperature and moisture that can be obtained are
just what is needed for a perfect cure.
As the curing proceeds an alternating change from the moist to the
dry condition of the leaves takes place, according to the atmospheric
conditions. Practical experience has proved that a frequent change of
this kind is desirable.’ This agrees also with the theoretical inference.
There is more oxidase in the ribs than in the mesophyll, and by the
alternate drying and moistening the evaporation from the surface
causes a current of juice to pass from the ribs to the mesophyll cells.
This migrating juice finally distributes most of the oxidase from the
bundle sheath and sieve tissue uniformly through the leaf. It is there-
fore desirable to have the ribs keep alive much longer? than the rest of
the leaves, since deau and dry ribs would not support the process
indicated.
As long as all the cells of a leaf are alive a current of organic mat-
ter—especially sugar, and also to a small degree, amido compounds—
takes the opposite direction, namely, from the lamina to the ribs. Grad-
ually this function stops, since a state of starvation sets in when the
starch, in the form of sugar, has been transported to the stalk and
consumed by respiration. The decrease of soluble albumin in the cur-
ing process is much slower than the decrease of starch. Even after a
fortnight a moderate amount is left, and with single cured leaves, even
after four weeks, some traces of it were found in the tissues.
DECREASE OF ACIDITY.
It is an interesting fact that the acid reaction decreases in the lamina
as the curing proceeds, as shown by the following table. For 200 sq.
em, there was required the following amounts of one-tenth normal soda
solution: :
Uppermost | Lower
Date. a | leaves.
Cae C. C.
AWM SUSH Ts Po ee Sac ee we a eee ce eee ST a 3.8 3.0
AOS EG: Bears F55 5 ree lac he Sats ae a ap cee ne ge | 3.3 2.3
AMOUSE V4 stk Bee Sa are ee ene on = a 2.5 a
September 26 5san 25h ooees See ee ee ee eee ea ho pp es Berea 1.7 9
'Report No. 62 (p.12), U. S. Department of Agriculture, by Marcus L. Floyd.
This report also contains views on the best construction of the usual barns.
“The midrib may remain alive for three weeks and over.
.
29
At the end of the curing process the amount of free acid for a given
surface was therefore reduced considerably.' A portion of the acid
may have passed into the stalk, another portion may have been com-
pletely oxidized, and another may have been neutralized by ammonia
formed in the destructive action of oxidizing enzyms on nitrogenous
compounds. In the subsequent sweating process the liberation of
ammonia is more energetic, and neutralizes the rest of the acid. The
decrease of acidity in the curing process is of practical importance,
since the following sweating process will set in with sufficient energy
only when the reaction is nearly neutral. The practice of the tobacco
manufacturers in Florida of applying a spray of ammonium carbonate
solution when the ‘“‘hea»ys will not heat up well” is therefore in accorda-
ance with the scientific inference.
BEHAVIOR OF THE OXIDIZING ENZYMS IN THE CURING PROCESS.
In a normally conducted curing process, whether curing single leaves
or curing on Stalk, the oxidase and peroxidase are well preserved. This
is not the case under conditions unfavorable to a normal curing. The
oxidase especially loses its active character more or less. Flue curing
seems just as injurious’ as prolonged moist weather. The acidity in
the leaves is, according to the writer’s observation, generally too weak
to cause injury; but the occasional entrance of too much sunlight into
the barn may diminish the oxidase in the exposed leaves. Reynelds
Green, and Brown and Morris have shown that enzyms, as, for example,
diastase, are injured by exposure to direct sunlight, while with regard
to the action of water it has been shown by Laborde that a gradual
destruction of oenoxidase takes place within twelve days by self-oxida-
tion when it is dissolved in water and exposed to air. There can
hardly be any doubt that much water retained for a certain time in
the curing leaves of the barn will favor self-oxidation of the tobacco
oxidase. This is also shown by the following test.
A large upper leaf was placed in a covered glass cylinder contain-
ing some water, to insure ap atmosphere saturated with water vapor.
After being kept in darkness for a week at from 22° to 28° C., compari-
son with a normal leaf showed less oxidase in the parenchyma of the
leaves so treated than in that of equally old fresh leaves of the same
plant, while with the veins the difference was not so marked. On the
other hand, no decided decrease of peroxidase could be noticed.
‘In the pith and bark no decrease of acidity, but, on the contrary, a slight inerease
was observed during the first two weeks of curing. Further it may be mentioned
that the acidity seems to decrease more slowly when the leaves are single cured than
-when cured on stalk. Only one test was made, however, in regard to this.
2F lue curing is mainly used in the curing of the bright yellow tobacco of Vir-
ginia, Tennessee, and North and South Carolina. The temperature reached thereby—
71-79° C. (160-175° F.)—is detrimental to the oxidase. Such tobacco, however, is not
subjected to sweating.
30
Furthermore, according to Mr. Mareus L. Floyd, it is a known fact
that tobacco too long ‘in case” because of prolonged moist weather
will sweat but very imperfectly. The poorly sweated crop of 1898 in
Connecticut also showed much “canker” and ‘pole burn,” conditions
favored by too moist weather. —
When it happens that tobacco does not sweat well, or even not at all,
it may be too acid or may have lost its oxidizing enzyms through irreg-
ularities in the curing barn, or it may be too poor in the proper
oxidizable material. The writer was assured by tobacco growers of
Connecticut and Massachussetts that tobacco grown in very dry years
is incapable of sweating; [871 was such a year. Even the transpor-
tation of the tobacco to the West Indies and back, an experiment tried
by Mr. Barnes, of Hatfield, Mass., to enforce a natural sweat, did not
change the rank smell of the cured to the aromatic odor of sweated
tobacco.
The writer was informed in Lancaster, Pa., that the crop raised there
in 1881 required nine years to reach the proper quality by means of the
natural sweat. Here probably a gradual oxidation without oxidases
has produced finally a result similar to that reached in a short time in
presence of the oxidizing enzyms.
Since it is the energetic oxidation in the sweating process that yields
a cigar leaf of superior quality, it must form one of the principal aims
ot a tobacco farmer to preserve the oxidizing enzyms while the tobacco
is curing in the barn. In the process of sweating, however, there is
generally a gradual decrease of oxidizing enzyms going on, the high
temperature favoring not only the action of these enzyms on oxidizable
material, but also the oxidation of the enzyms themselves. Practical
experience long ago found it necessary to take apart and rebuild the
fermenting piles as soon as the temperature reached about 60° C.
(140° F.). Indeed, if the temperature be allowed to rise much higher
there would be a rapid decrease of oxidase, and all the improvements
hoped for would come to a premature end.’ The relative amount of
water in the fermenting piles or cases will also exert an influence. The
peroxidase suffers less than the oxidase, but the former is probably of
very much less importance than the latter in the sweating process.
Investigations on this point will be carried on at some later time when
occasion offers.
TESTS FOR OXIDASE AND PEROXIDASE IN CURED AND FERMENTED
TOBACCO.
In regard to the tests for these enzyms it must be pointed out that
from the absence of oxidase in a tested sample it does not necessarily
follow that all of the leaves from the same curing barn would be
‘A full account of the temperature changes in fermenting piles of cigar leaf tobacco
is given in Report No. 60, U. S. Department of Agriculture, by Milton Whitney and
Thomas H. Means.
31
devoid of it. It may be that the leaves tested came from near a barn
door which was perhaps frequently opened, thus freely permitting the
destructive action of the sunlight. Therefore in controlling a curing
crop in the barn leaves should be tested not only from near the wall,
but also from the more central part of the barn.
‘The test was at first made in the following manner: The tobacco
leaf was deprived of the large ribs, and after drying at a temperature
of 40° C. (104° FEF.) was very finely pulverized. One gram of this dry
powder was mixed with 20 ¢. c. of water and left to stand for five
hours in an Erlenmeyer flask at the ordinary temperature. To 10 c. ¢.
of the filtrate a few drops of an alcoholic solution of guaiac resin were
added and the mixture was left to stand for ten minutes, with moderate
shaking. } Hatheld)) Mass: ground |-Wittle- {2-2--.c--2.-5|-o55< dOnseaseecs Do.
| _ leaves. |
Dec; =| Remedios: Cubasecces-es- INONCRasc coe aee eee Mulchaeeeeeecs Crop of 1899.
Rardido, Culbassce2- eee ane dome ceerenceeee Slight trace... Do.
Hiaibigwaeos -cenecascceeees MTACO LES seice eee sees Miurcheeee ce Do.
PMeLtOnRicCO aoseceeeeeee INONG ieee eee Moderate .-..- Poor grade, 1899.
IEWAIVAKOARIED socosugubeosellecoae (WO) setae Sketeer lee Gye henaus Best grade.
We learn from these tables that the flue-curing process is unfavor-
able for the preservation of the oxidizing enzyms, and that sweated
tobacco has frequently lost its entire content of oxidase, while the per-
oxidase is more resistant under the conditions of the sweating process.
From the absence of oxidase in fermented leaves no conelusion can, of
course, be drawn as to its amount before the sweating was begun.
The more intensely the sweating process is carried on, the more of these
oxydizing enzyms will be destroyed.
TEST FOR CATALASE IN VARIOUS TOBACCOS.
With regard to catalase, the third oxidizing enzym of tobacco men-
tioned above (page 22), some experiments were made on various samples
of cured and sweated tobacco to determine the amount of oxygen devel-
oped by it from hydrogen peroxide in from fifteen to forty minutes.
From the energy of this action inference may be drawn as to the rela-
tively larger or smaller quantity of the enzym in different samples.
Tobaccos that had been fire-cured, as the plug tobaccos, contain in
most cases neither oxidase, peroxidase, nor catalase. Such samples
examined were bright yellow Virginia, black African, and English olive-
green leaf. A sample of Burley tobacco showed, however, slight traces
of peroxidase and catalase. Since the temperature in this curing
method often rises as high as 82° C. (180° F.) these observations do not
surprise us. Also a flue-cured sample of yellow tobacco from North
Carolina did not show traces of the three enzyms. Such tobaccos are
not intended for cigars and are not submitted to the sweating process,
hence the absence of the oxidizing enzyms is here not of any conse-
35
quence. But there are also conditions in the usual treatment of cigar
tobaceo which may injure the catalase. Thus no trace of it was found
in one sample of sweated tobacco from Connecticut of 1897. In most
cases, however, catalase is retained in the sweated cigar tobacco for a
much ionger time than either oxidase or peroxidase.
The comparative tests for a and / catalase were carried out in the
following way: The air-dried samples were very finely powdered after
removal of the midrib. After remaining twenty-four hours in an exsic-
cator 2 grams were extracted for five hours with 40 ¢. c. of water at the
ordinary temperature with frequent shaking, and then filtered through
filter paper. Twenty cubic centimeters of the filtrate were mixed with
5 c. c. of neutralized commercial hydrogen peroxide. The development
of oxygen by the soluble or 6-catalase commences a few seconds after
mixing. Then the extracted tobacco powder was, after washing, sus-
pended in 30c. c¢. of water and 10 ¢. c. of hydrogen peroxide added.
The oxygen here developed was due to the action of the insoluble
or a catalase. The proportion of the developed oxygen gradually |
decreased in all cases after a short time, since the hydrogen peroxide
in the concentration applied oxidized and killed the enzym rather soon. .
The reaction was promoted by moderately shaking the flask.
In those cases in which after a rapid development of oxygen gas an
early stop was noticed a second dose of hydrogen peroxide was added,
which was repeated as cften as found necessary until the reaction had
been carried on for a given time.
It will be noted from the method of testing just described that the
data relating to 6-catalase are obtained from 1 gram of tobacco; those
relating to a-catalase from 2 grams.
Thus far no data are known that would enable us to calculate the
absolute weight of catalase from a certain volume of oxygen developed
in a given time by the decomposition of hydrogen peroxide. But quite
generally we might make the following distinction as to relative quan-
tities. The amount of a-catalase is small when under the above-
described conditions less than 50 ¢. ce. oxygen are developed in fifteen
minutes by 2 grams of tobacco; it is moderate when between 50 and
200 c. ec. are developed, and high when the volume rises above 200 ¢. ¢.
As to /-catalase the amount may be called small when less than 20
ce. c. of oxygen are developed in fifteen minutes by 1 gram of. tobacco;
moderate, at 20 to 100 ¢.c., and high, when the volume rises above 100.
36
Oxygen developed.
: om; | | : | Peroxi 2
Sample. Toe By a | By B- Oxidase. | dase Remarks.
srs catalase. | catalase. |
|
Minutes. | Cac Calc:
5 | 22 | Oo | pSSoos cos a|eesee asses
Connecticut broad- 10 34 | 1.8 | Moderate -| Much.--. lence: 1899, but not
leaf. | 15 | 42 QHO MESS ees SOIR re eae { sweated.
30 | 66: | By aed he Deeps a ate
5 32 | aot ace ee ee oe Some...
10 45 | 19% Sei) INON@ ssn - 5 hese seen
Florida, 1897....-.-:- 15 76 | Ps a eee ip ee Se ac ad Sweated in bulk.
20 84 2920) (S250 Sec bee See
AQ: Nee eerie 3656) Ponca ane S| Se a eee
5 12 B50y| ee eee toe e ei oe ue ;
Maryland smoker, 10 22 WAS Sse seem anaes |-z2 c-2---- Eght clores Ae 4d
xQ 45 9 « zs . Ds : 4 «0 J ,
i898. | ae a ees 13.2 EES S2a Re |, cone : slightly in bulk.
5 108 | A Be eae [Sentara
ihe. a P 10 174 | S50 70NeNOner ose Trace..--. |Crop of 1897, sweated
ohn Zo Spi “od epee cus ae 40.5 | — es a pulie So eee
Spee gah = onl Nonew = Neneees
Wisconsin, crop of | 10 40 | 7 pitaye sue] eas it
1897, ““Gummy” | 15 46 iLOup ake os aes Koei hae? ae |\Natural sweat.
leaves. l| 9 Soot | ak? pe tara coreg |
| 20 AG tl = tbs Fm eae eens eee mee
5 32 160, | Gcsocbecasee pee et ones
ig 2 SS SNE None -- Moderate. passed through the
Pennsylvania -.----- | ee at iene saci el W ESE Op Eiit es eee ‘*natural’’ sweat,
20 76 16! Sys Se ee Hence
320 SG ase ce ee sal oe eee crop.
40) Corb Se5. Lares ee ee a ee
| 5 Zilia See le eee eee i
Remedios, Cuba.--.-- | 2 ‘6 P None -..__| Much. -- “| Sweated, 1899.
20 71 SOM cheat ees eae eegese tie te
i( 5 | 14 Sa cee es ae Lge ae
| 10 20 11.0 | None -.... | Trace...
Pardido district, Cuba 15 24 | 14 On eee es | SRS EAS Ae Sweated. 1898.
20 27 Tee ose ee see ee -
40 3G) here Sas aoe [ere eae ae Tae ee ae
5 16 | 3200 ences aes ee ee ee eee
IARAKO GOseoccascac 10 20 | Aish 7 2 peat Ee BE are es | eke eee |sweated, 1899.
15 25 | Hotel None eae
Enttless=:
It was thought that it would also be of interest to test cigars
of commerce for oxidizing enzyms.
Of the samples procured, which
were probably of very different ages, not one contained oxidase or per-
oxidase, but catalase was present in all, although the amount differed
considerably to judge from the energy with which hydrogen peroxide
was decomposed.
As to cigarette tobacco, five different brands of
cigarettes were examined, viz, Old Dominion, Sweet Caporal, Gold Leaf,
Chesterfield, and Egyptian Prettiest, but only in the last named was
any catalase fou
nd.
Oxygen developed in fifteen minutes.
]
By a-cata- |
Arena
Haranettsee eee eee
Marquis L
Lucke Rolled
Union Glory
La Valiar
------ ce aeeecceee
Herbert Spencer -.---- 2
General Arthur
No name
Egyptian cigarettes...
Cigar samples. Price. Tae By eae
Cace ex:
Sead eiene Se ciele se eete esti s = eles eeeeeaene 3 for 5 cents --| 91+ 5.5
sett Seed SS ee Ss cea 2 for 5 cents -- 520 41.0
Bouse SeSctesdosbeoe csc St oeetaccnoesese | 5 cents---...-. 71 13.2
soe eee SEN a ae et es er ee ee 41 18.0
Sue chested cee lo SRS eee ee eee eee Fieentsacs soso 85 8.0
Bee ese Hoe aOR ERS OSOE Se’ LOlcentse-ee-e— 26 3.0
| SFgre SS ar Se Sere Oye epaeicie( (gees Sie 273 2925
ShcA 2S yt) gs gee 2s sO ean el mae oe a TRANG (iveoiens ase 304 1353
SN ee etek es Be a ae Ses 2 cents a piece- 61 8.5
Nasi t Seats eet eee ee 5cents a piece- 102 17.5
SoS or Seer Ne ea ne eh eS, REE eg A a SP ce dO shee 108 3.2
eee ree os Sar aay tsi Me ee ane ae Be ee does 32 3.8
ie tee A See I ee ear pee ee 241 55.0
So BEE See en, Soe ae ee ee ee Pes mst SNe 5 eee 36 2.0
37
It will be noticed from this table that there is no direct relation
between the commercial value of a tobacco sample and its catalase
content. On the one hand, however, it may be said that a comparatively
high content of soluble or /-catalase would be indicative of this tobacco
having been subjected to a sweating at a higher temperature, since the
ammonia developed renders some catalase soluble. Further, since a
thorough sweat is essential for the development of aroma, a high content
of soluble or 6-catalase would indicate an improved aroma, other things
being equal. On the other hand, it might be inferred that a sample
containing very little soluble, but comparatively much insoluble catalase
(see No. 11 of the above table), has passed only through the natural
sweat and could be improved by a subjection to sweating in bulk
after petuning with a very diluted solution of ammonium carbonate.
- In order to reach a reliable estimate of the extent of the transforma-
tion of the insoluble into the soluble catalase by the sweat only leaves
of equal age and very similar to each other should serve for compari-
son. A cured leaf can not be compared with a sweated leaf of the
same crop when the former happens to be a lower or sand leaf and the
latter an upper leaf. Neither can thin, strawy leaves be compared with
gummy leaves, since the differences between these are very great in
regard to their enzym content. Thus, a not sweated, very thin, prob-
ably a sand leaf, yielded in fifteen minutes by the above test 7.7 c. c. oxy-
gen for the soluble enzym and 69 c. c. for the insoluble, while a sweated, -
guminy leaf of the same crop yielded 147 ¢. c. and 360 ¢. ¢. oxygen,
respectively. There can be no doubt, however, that the above tests,
judiciously carried out, may prove of practical value in certain cases
In order to obtain comparable results, and to eliminate the factor of
individual differences, upper leaves which can be distinguished by their —
heavier body were picked out of a lot of cured leaves and of a lot of
leaves sweated in bulk, of the same crop.! After moistening them a
little they were left over night until they became pliable, whereupon
they were spread out and the adhering sand carefully brushed off. The
central portions of 12 leaves were then deprived of the midrib, and
after drying at 40° C. (104° I’.)? finely pulverized. Two grams each of
this powder were weighed out, and the tests carried out as above men-
tioned. The result was as follows:
Oxygen developed in thirty minutes.
Srreduo ud notisweaved tiller leavesy-o see cots esos chee cence coecae aomeee cere ; 158 16. 5
Cmnedeanars weabeds tiller leaves). sacece a eacese ne hese wee ones ace wioseene ese 634 236. 0
ETOpOLuions of the volumes) Of, Oxy 2 eONets se.
>This liquid was prepared from licorice and various condiments, with addition of
some rum, according to the prescription given by Marcus L. Floyd in Report No. 62,
U.S. Department of Agriculture, p. 19, Cultivation of Cigar Leaf Tobacco in Florida.
tira.
39
influence of concentrated sulphuric acid upon the “grain.” Although
there is some calcium oxalate present in the living leaf, the oxalic acid
of those globules is produced by post-mortem oxidation, since they do
not exist in the living leaf, the natural inference being that it is the
oxidizing enzyms that produce them by inducing oxidation of various
compounds, such as malic or citric acid, tannin, etc. The more oxidiza-
ble material, and the more oxidation is going on in the tobacco. leaf, the
more will the so-called grain develop in the curing and sweating proc-
ess; hence it will in many cases, by no means in all, confirm the idea
of some tobacco manufacturers that a well-developed grain is a good
sign for the quality of the tobacco.
The following observations by the writer may be mentioned: A fresh
tobacco leaf was divided into two portions. One portion was hung up
ina covered beaker containing some water, the other was first heated
to 60° C. (140° F.) in a closed vessel before being thus treated. By
the sudden killing of the cells by heat the cell sap left them at once
and spread uniformly over the surface of the leaf, while in the former
case the gradual drying and the later death diminish the migration of
soluble matter to the surface. After eighteen days the “ grain,” in the
form of numerous giobules of calcium oxalate, was formed in the nor-
mally curing leaf, but not a trace of it was seen in the leaf killed imme-.
diately after collecting it. This shows that these globular masses were
formed in the curing process. In the fresh leaves deposits of calcium
oxalate also occur aS mentioned, forming crystalline sandy deposits,
especially in mesophyll cells. Generally these seem too small to account
for the appearance of the “ grain” in cured and sweated leaves.
The nature of the “ grain ” was also investigated by Dr. W. C. Stur-
gis, who arrived at the same conclusion as the writer and at about the
Same time. That author had the kindness to communicate the follow-
ing observations:
The crystalline deposits are insoluble in water, but are completely and readily
soluble in dilute hydrochloric acid. On heating, these deposits swell to three or
four times their original volume. Examination under the microscope of these
heated masses in water, with the addition of hydrochloric acid, show that they are
at once dissolved with copious evolution of gas. These observations, coupled with
what we know of the occurrence of calcium oxalate in leaf tissues, lead me to con-
clude that the grain of certain grades of tobacco is caused by the deposition in lim-
ited areas of crystalline aggregations of this salt. ©
REMARKS ON THE DEVELOPMENT OF THE BROWN COLOR.
The slow starvation process of the tobacco leaf in the curing barn is
connected with the yellowing of the leaves, followed by the character-
istic brown. The yellow color is chiefly due to the etiolating of the
chlorophyll granules because of the absence of bright daylight, and
sets in while the cells are still alive, while the brown color sets in after
their death. The changes of the green to yellow and of the yellow to
brown start and proceed generally in the same order, commencing
at the margin and about midway between the lateral veins. Along
AQ)
the thicker part of the veins the tissue remains green longest. Gradu-
ally a stage is reached in which only the midrib and basal parts of the
lateral ribs still have their normal color, being fringed by but narrow
strips of yellow mesophyll, the chief mass of the leaf having turned
brown.! Thus, the layman is inclined to infer that the substance
which turns yellow is also the same that turns brown later on. This,
however, is not correct. The yellow color is due to a chemical change
of the cllorophyll green, while the brown color is due to the oxidation
of several different compounds contained in the cell sap. The brown
color shows also in the veins of the leaf, but not the yellow, since there
is too little chlorophyll in the veins. It sometimes happens, however,
that leaves in the barn die quickly by drying up instead of slowly by
starvation, thus not allowing sufficient time for development of the
yellow color, and in this case the brown color develops directly upon
the still green leaf. Such leaves show a distinctly green coloration when
held between the eye and the bright daylight, and on treatment with
strong alcohol they yield a green solution of chlorophyll, showing that
the green is not destroyed, but merely concealed by the brown. The
chlorophyll, therefore, is not the source of the browncoloration. Further-
more, when afresh leaf is dried at a moderate temperature in an air bath
it will no longer turn yellow when exposed for a considerable time to
a moist atmosphere, showing that the change from green to yellow in
the curing barn is still a process of life, although a pathologic one.
As to the brown color, it can easily be shown that it is produced by
the action of oxidase and not by the action of peroxidase, since after
“killing” the oxidase the brown color fails to develop. Freshly
expressed juice of the midrib was heated for four minutes to 75° C.
(167° F.) and left with a little chloroform in a flask plugged with
cotton. After ten days this liquid was still colorless, although con-
taining peroxidase, while the control liquid became light brown within
one day.? The juice of the lamina turns dark brown much sooner.
WHY DOES THE OXIDASE NOT PRODUCE THE BROWN COLOR WHILE
THE LEAF IS ALIVE?
The oxidizing enzyms are evidently contained in the plasmatic living
part of the cell, and not in the cell sap which fills the vacuoles. On the
other hand, the matters easily oxidized by them and representing
products of metabolism or by-products of certain synthetical operations
are mostly contained in the cell sap. These matters, often of a chromo-
1The brown color darkens still more during the sweating process. When the
expressed juice of green tobacco leaves, after filtering, is exposed to air it gradually
forms an insoluble deposit, the greater part of which consists of a phlobaphen-like,
dark-brown substance, and the smaller part of a colorless flocculent compound. The
former is easily soluble in dilute ammonia; the latter is not.
*It may be mentioned here that, according to A. Mayer, a dark-colored tobacco is
obtained by a rich nitrogenous manuring, and that, according to Kosutany, barn-
yard manure with ammonium salts yields a product of a reddish brown tint, while
nitrate manuring yields a more greenish-brown one.
Al
venic character, are, of course, produced in the plasmatic parts, but
secreted rapidly into the cell sap. When the cells die the soluble sub-
stances locally separated in the cytoplasm and the cell sap intimately
mix, sincethe coagulating protoplasm, becoming easily permeable, can no
longer retain any soluble matters—as, for example, oxidase. Thus after
death the direct action of the oxidase on the oxidizable matter of the cell
sap sets in with a production of colored bodies, as is the casein the tobacco
leaves. This action can also be noticed very well in the juice pressed
out from the fresh leaves, since this juice, containing cell sap as well
as soluble matters previously contained in the protoplasm, turns brown
rapidly on coming into contact with air. The darkening of the juices
of potatoes, beets, and other plants depends upon the same principle.
CHROMOGENS OF TOBACCO.
The nature of the chromogenic compounds has not yet been fully
revealed. It was pointed out in Report No. 59, p. 12, that several dif-
ferent compounds have to be assumed as contributing to the color in
the tobacco leaf, and that tannin as well as nicotine contribute only a
partof it. It is true that the darker tobaccos are generally considered
aS being the stronger—that is, contain the most nicotine—but, on the
other hand, it has to be kept in mind that the veins, which contain less
nicotine than the lamina, are generally much darker colored, a fact hardly
to be explained merely by the thicker layer of cells. The fact, how-
ever, that the juice of the lamina turns dark more quickly and intensely
than the juice of the rib makes it probable that the chromogen of the
ribs is not easily soluble and differs from that of the lamina. In the
lamina it is the mesophyll and not the epidermis that contains the chief
quantity of the chromogen.
The main chromogens of the leaves are insoluble in alcohol, as is the
brown product itself. Thoms obtained 88 grains of ammonium sulphate from 15 kilograms sweated
tobacco on distillation with steam; but only a part of the ammonia is obtained in
this way. Various analyses give from 0.05 to 0.5 per cent ammonia in tobacco.
46
allowed to reach 65° C, (109° F’.), as Van Bemmelen reports. When
this temperature is kept up for some time or is allowed to rise some
degrees higher, the tobacco loses its power of heating up again when
the heap is repacked. The oxidase and catalase are now killed.
Such tobacco is called “cooked.” It is knotty and curled and the
fiber has lost much of its elasticity.”
NOTES ON THE BACTERIAL HYPOTHESIS OF SWEATING.
Although it was shown in Report No. 59 that Suchsland’s bacterial
hypothesis of the sweating of the tobacco is unfounded -and that the
true cause of the oxidation in the sweating process must be attributed
to the presence of oxidizing enzyms in the tobacco leaf itself, never-
theless some persons still adhere to the bacterial hypothesis. Butitis a
simple matter for anyone to convince himself by direct microscopical
examination of scrapings from moistened sweating wrapper leaves that
the numerous bacteria which would be expected, by the hypothesis,
are not there. Even if we assume that the supposed tobacco bacteria
are characterized by extraordinary capacities of oxidation and fermen-
tation, and that therefore a restricted number might account for a
great deal of work, several millions at least should exist for every
square inch. Further, it is evident that the conditions on the tobacco
leaves are most unfavorable for bacterial growth. It was pointed out
by the writer that the water content of a fermenting wrapper leaf is
utterly insufficient to bring the nutritive compounds from the interior
of the cells to the surface, the moisture being barely sufficient for the
proper imbibition of membranes and cell contents. The easily soluble
matters, such as oxidizing enzyms, will no doubt dissolve, but this solu-
tion will be retained in the chief mass of the cell contents.
Let us assume that all the water of a sweating leaf would be ayail-
able for the cell contents—none being retained by imbibition of the cell
membranes—and, further, that one-half of the cell contents is easily
soluble in water, although in reality two-thirds are easily soluble in
their own weight in water. A fermenting wrapper leaf with a water
content of 20 per cent® would then contain a solution of organic matter
of a strength of 50 per cent, since ripe wrapper leaves of good quality
and capable of fermentation contain in the dry substance an average
of 40 per cent of matter soluble in water.* In such a solution of 50 per
cent of organic substances bacteria can not multiply. Even mold
'Landw. Vers. Stat. vol. 37, p. 383.
2 This is the experience of tobacco manufacturers of Florida, and has been men-
tioned to the writer by Mr. M. L. Floyd.
°'The tenacity and cohesion of wrapper leaves are generally seriously injured as
soon as the water content is increased above 27 per cent while the sweating is
going on.
*Of course the percentage of soluble matters varies considerably in different
grades of tobacco.
Aq
fungi find it rather difficult to live under those conditions.' In reality
the conditions are still much less favorable for bacteria than we have
assumed in this calculation. The high temperature is also an obstacle
to most bacteria. Fermenting wrapper leaves sometimes reach a tem-
perature of 60° C. (140° F.), and still ferment again when the heap is
repacked. It would be a very easy matter to isolate the active bacteria,
if they should belong to the few thermophylic kinds that can be active
in such a high temperature. But nine yeais have passed since the
promulgation of the bacterial theory of tobacco fermentation, and thus
far there is nowhere to be found a scientific description of the supposed
tobacco bacterium.
The following experiment shows that bacteria from the very surface
of the tobacco leaves can not thrive in a concentrated tobacco extract.
Such an extract containing 30.2 per cent of sotid matter was sterilized
and a small piece (about 1 cm. square) of a freshly cured tobacco leaf?
introduced, after which the flask was plugged with cotton. After 10
days neither a seum nor a turbidity indicating the presence of bacteria
could be noticed, but some clot-like masses were observed. ‘These
masses proved to consist of a mycelium of a fungus, while even with
the highest magnifying power no microbes could be observed. How-
ever, a dilute solution, prepared by diluting the former with ten times
its volume of water, formed a bacterial scum within two days upon
exposure to the air.
In a second trial, with a concentrated solution of 25 per cent of
tobacco extract (contained in a test tube) exposed to the air for ten days
to admit various kinds of microbes, there was neither a scum nor a
bacterial turbidity produced. On microscopical examination, however,
some few bacteria could be noticed. Now, if solutions of such concen-
trations are so very unfavorable for bacterial growth, how much more
must this be the case for the much higher concentration to be found in
the cells of the fermenting wrapper leaves?
Further experiments proved that even at a water content of 35 and
40 per cent present in fermenting fillers* bacteria can not flourish upon
the leaf surface at the temperature of the fermenting piles. In freshly
cured heavy tobacco the water was determined and enough water added
so that in two samples the percentage reached 35 and 40 per cent,
respectively. These leaves were rolled up and placed in flasks, which
were sealed with paraffin and kept for five days at a temperature of
from 53° to 55° C., there being an abundance of air in the flasks. For
1 According to Splendore (Revista Tecnica, Roma, 1899), Ocspora Nicotiane can not
develop upon tobacco that hag less than 26 per cent of water, and, according to
Behrens (Landw. Vers. Stat., Aug., 1899), Botrytis requires at least 30 per cont of
water in cured tobacco to be able to grow on it.
2This tobacco contained catalase, oxidase, and peroxidase and was subjected to
“sweating” or “‘fermentation in bulk.” It sweated normally.
* Hands of filler tobacco are dipped with their base deeper into the water than
hands of wrapper tobacco, thus securing a higher water content.
48
a short time the temperature reached 59°, but since even 60° is fre-
quently observed in the fermenting tobacco piles this temperature
should not be expected to kill the supposed tobacco bacteria. The
microscopical examination of the leaves after five days proved the
absence of a bacterial coating: Only here and there a microbe was
found, but upon staining and counting in everything which had any
resemblance to a spore or bacillus there were not more than 600
microbes to the square inch. The examination was made not only of
scrapings of the moistened surface, but of the triturated parts of the
leaf itself.
Recently a treatise by H. Vernhout has appeared in which a microbe
closely related to Bacillus subtilis is described from fermenting tobacco
leaves in Java.! The author ascribes to this the phenomena of tobacco
fermentation. The proof, however, that this microbe can produce fer-
mentation and can multiply on tobacco leaves with only 25 per cent
water has not been adduced. His further remark that a sample of cured
tobacco did not contain any oxidase or peroxidase does not require any
further comment, since these enzyms may disappear as above mentioned
under unfavorable conditions, while catalase, the third oxidizing enzym,
still may persist.
SWEATING MUSTY TOBACCO.
The complaints about ‘‘musty tobacco,” ‘white mold,” and ‘ black
rot” in tobacco packed in cases are quite frequent. Moist weather
toward the end of the curing, and especially while stripping and pack-
ing are going on, favors these injuries. Apparently quite healthy
tobacco will often, after having passed through the natural or cold
sweat, have a moldy odor? or a cover of a white film of fungus
mycelium, or even patches where the leaves are transformed into a
powder by the so-called black rot.’ Dark heavy tobacco is said to be
most damaged by ‘white mold.” Because of this damage the value
of the tobacco is decreased to about one-sixth of the original. A
tobacco manufacturer assured the writer that out of 1,600 cases of
tobacco of a particular crop he found 1,300 cases more or less
damaged in this way, and he estimated the damage annually caused
in this country at about $1,000,000. Repacking after removing the
worst portions affords but a poor help and but for a short time.
In the case of black rot further serious damage can be prevented
more easily by repacking, since this fungus does not continue to
spread after cold weather sets in in autumn. The chief remedy
'Onderzoek over Bakterien bij de Fermentatie der Tabak, Batavia, 1899.
The moldy odor is caused by the growth of the common mold fungus, Penicillium
glaucum.
°In a case of black rot examined by Mr. E. A. Bessey, in which the cohesion of the
parts of the leaf was destroyed and patches of it transformed into a pulverulent
mass, the fungus Sterigmatocystis nigra (Aspergillus niger) was found.
49
applied at present is a “forced sweat,” in which the musty odor
disappears and the mycelia of the fungi are killed; but when this
process is not thoroughly carried on the spores may be uninjured, and
thus it happens that the musty odor may come back again when these
spores develop.
This forced sweat is carried on in the presence of much aon ees or
50 per cent—and is therefore suitable only for fillers, since under such
conditions the wrapper leaf would deteriorate considerably. The writer
has observed that with a room temperature of 26.6° C. (80° F.) and a
water content in the tobacco of 47.6 per cent the temperature of a large
box filled with such moistened musty tobacco was markedly increased
within four hours, and in two days reached a temperature of 40.5° C.
(105° F.). From three to four days are allowed for this sweat in sum-
mer, and from one to two weeks in winter.! Tobacco that has passed
through a “forced sweat” will not again heat up sufficiently, while
after a cold or natural sweat it will heat up readily.
Some suggestions might be made as to how to prevent, as far as possi-
ble, the deterioration of cured tobacco by fungi. Whenever the stripping
cellars are underground or immediately under the curing barn, the
moisture of the air in the cellar often increases to such an extent that
the stripped tobacco absorbs too much moisture before it is packed.
When the water content of tobacco rises above 30 per cent there is great
danger of the development of fungus spores which may be present on the
tobacco leaves. Besides, in such damp localities various fungi develop
on the floor and walls where organic impurities have gained lodgment,
and hence the opportunities for the infection of the tobacco in the
Stripping process are much enhanced. Some farmers have recognized
this dangerous source of infection and fumigate the stripping cellars
with burning sulphur before commencing the work. The mycelia of
fungi can easily be destroyed by this process, but the more resistant
spores may escape destruction. Another means of cleaning the cellars
is to whitewash them several times with freshly slaked lime and dry
them out well with artificial heat before the stripping commences. It
would be still better to have the stripping localities above ground and
have them kept warm while the stripping is going on.
An essential step of progress would be made by giving up altogether
the natural or cold sweat and by replacing it with the ‘sweating in
bulk,” to be carried out soon after the curing process is finished. The
fungus spores, the germination of which is hastened by heat, are grad-
ually killed in that state when the temperature rises above 50° C., and
thus the fungus development injurious to the tobacco is easily avoided.
A few words may be said in this connection about measures for the
prevention of stem rot. ‘Stem rot,” a disease sometimes developing
and spreading in the Cone barn, ee been investigated by Dr. W. C.
1Suh resweated tobacco is eee not packed again, but serves directly for
the manufacture of cigars.
20914—No. 65
50
Sturgis, who named the fungus Botrytis longibranchiata.! He recom-
mends that all the diseased stems and leaves be collected and burned
at once, before the fungus is further developed and before its spores
can be scattered about by any current of air. He further suggests
sprinkling the floor of the barn with a mixture of equal parts of air-
slaked lime and sulphur, and the fumigation of the tightly closed barn
with burning sulphur a fortnight before the tobacco is harvested, and
again after the removal of the cured tobacco from the barn. It may be
added here that washing the floor with thick milk of lime which has
been recently slaked in the usual way has also been found beneficial.
AROMA OF THE TOBACCO.
The odor developed in smoking a cigar may be partly due to the
mere volatilization of products of the sweat and partly to the destruc:
tion of certain compounds. The heat of the glowing surface reach-
ing the neighboring sections which are not in full contact with air
~ causes there volatilization and various decompositions by dry distilla-
tion. Products of pleasant and of unpleasant odor are components of
the smoke, and it is the chief aim of the progressive dealers in the
tobacco trade to reduce the amount of the latter components to a mini-
mum. In the smoke of tobacco have been found besides carbonic acid
and water, nicotine, ammonia, carbonic oxid, occasionally nicotianine
and traces of hydrogen cyanide, and hydrogen sulphide. Recently
pyridine, trimethylamine, and butyric acid have been found in it by
Thoms.? The pyridine is produced by the decomposition of nicotine,
while the hydrogen cyanide, hydrogen sulphide, and butyric acid are
probably derived from protein compounds.
The soil, climate, and weather on the one hand and careful treatment
in the curing and sweating of the tobacco on the other have great influ-
ence in the production of a cigar leaf having the proper aroma in
smoking. This flavor must be distinguished from the odor which the
sweated tobacco leaves show directly without being heated or smoked.
The writer proposes to designate the former alone as aroma, while the
latter will be called simply odor. The use of this distinction is made
in the following lines.
The odor of the sweated tobacco leaves doubtless stands in a certain
relation to the aroma generated in smoking, generally a pleasant odor _
justifying the inference of a fine aroma; but this is by no means always
so, and cases occur where a sweated tobacco of pleasant odor produces
a disagreeable odor on being smoked. The aromatic substances may
here escape perception because of the presence of other and undesirable
compounds. The substances which impart the odor are easily soluble in
water, since tobacco extracted with water and dried again has no longer
‘Conn. Agr. Expt. Station, Annual Report, 1891, p. 185,
*Chem. Zeitg., 1899, No. 80,
51
its characteristic odor. ‘Nicotine free” cigars made of such tobacco
’ are also devoid of any trace of aroma. Treatment with much alcohol
also removes the odor more or less, and this alcoholic extract on evapo-
ration at the ordinary temperature leaves a residue recalling the odor
of the tobacco. This residue upon treatment with ether can be sepa-
rated into a soluble and an insoluble part, but neither of these has any
odor, Showing that the substances which caused the odor are easily
volatilized or chemically changed. Indeed, they are easily changeable,
as can be observed when sweated tobacco is distilled with water. Five
hundred and fifty grams of Florida tobacco of a superior odor were
mixed with eight times its weight of water and nearly 500 c.c¢. were
distilled off. On the surface of the slightly turbid distillate, which had
a weak but rather disagreeable odor, resembling somewhat that of ran-
cid oils, minute oil drops were seen. Not only was the distillate devoid
of any specific odor, but also the contents left in the flask had lost the
original odor. The odor is also easily removed by dry heat. Two
hours exposure to air at a temperature of 100° C. (212° F.) suffices to
deprive tobacco of most agreeable odor of this desirable quality.
Tobacco leaves, even from the best tobacco regions, are by no means
distinguished by peculiar flavor in their fresh or cured state.’ The
curing exerts a beneficial effect upon the quality of the aroma only in
so far as a part of the protein is destroyed by it. Cured tobacco, even
from the best sources, has a mere straw odor. The fine odor and genu-
ine aroma are generated by the sweating process. The better regulated
the sweating process, the finer the aroma, other things being equal.
Whenever the sweat is not proceeding well—-ascribed sometimes to a
high fat content, or perhaps caused by imperfect curing, or by inju-
ries to the oxidizing enzyms in the curing barn—the product will have
a poor aroma. These circumstances make it clear that the original
resin in the leaves can not be the cause of the aroma, as some authors
have surmised. Indeed, the resinous matter from fresh or cured leaves
does not show any particular flavor when heated; neither has the ethe-
real oil contained in the hairs of the fresh leaves a beneficial effect on
the quality of the tobacco.
It is well known that it is especially the so-called gummy leaves that
sweat best and give the finest aroma. Such leaves are found among
- the upper and not among the lower or sand leaves, and are very rich in
extractive matters. When such leaves are shrinking in the process of
drying in the curing process, these soluble inatters may sometimes be
forced to the surface, to some extent, in the form of a concentrated solu-
‘While the juice of fresh tobacco leaves assumes, after a short time, the odor of
cucumbers, fresh leaves dried at 50° C., and afterwards moderately warmed with
water, gradually develop the agreeable odor of dried malt; an interesting fact, since
the germinating barley on the malting floor also at first develops the odor of cucum-
bers.
52
tion, hence such leaves feel sticky or gummy to the touch. By a thor-
ough sweat tuis ‘gum is taken out,” as the manufacturer says; in other
words these extractive matters are more or less oxidized.'! It is there-
fore of interest to determine the amount of soluble matter left after
sweating. This amount varies considerably, from 30 to 54 per cent.
The insoluble matter consists mainly of cellulose, lignin, protein, color-
ing matter, fat, resin, and ash. With some samples the following
results were obtained:
1p ere 3. 4
SPT e ya 2 Fae Sas esa ee ic Senge cnn Oe ae enna cpsesy a | 33:8] 37.5 44.3
Insolubles 22s ss ea stcs isstee Se oe es et eae eee See eee eee 62.9 | 66.2 62.5 55.7
Sample No. 2 showed saline efflorescences (so-called * saltpeter”) on
the veins. Sample No. 4 consisted of co-called ‘** gummy leaves.” The
ash varied from 19.4 to 22.1 per cent in those samples.
It was formerly believed that the aroma was chiefly due to the so-
called tobacco camphor or nicotianine—a crystalline volatile product
which was obtained by distillation of sweated tobacco with water.
Hermbstadt tried, as early as 1821, to isolate this aromatic principle.
On distilling various samples with six times the weight of water he
obtained a distillate yielding a precipitate with acetate of lead,
from which a crystallized compound of a strong tobacco flavor was
obtained, which he called nicotianine. Later on this product was
studied by Posselt and lhieman, and also by Barral. Two formulas
have been calculated from Barral’s results, namely, C.;H3N2O; and
C;3,H.;N;0;.. Barral states that it yields nicotine on distillation with
potassa. This product may possibly be formed from nicotine in the
process of sweating, but it is by no means contained in every tobacco.
A number of chemists have failed to observe it and the writer has tried
in vain to obtain it from Florida tobacco. The aqueous distillate from
the Florida tobacco contained, besides smail oil drops, some ammonium
carbonate, and the precipitate obtained with basic acetate of lead was
nothing but lead carbonate.? Probably the nicotianine is only an oc¢a-
sional product in very heavy tobacco. Odor as well as aroma is evi-
dently caused not by a single compound, but by a mixture of com-
'The word “‘gum” is applied in other countries in the same sense as the word
“life” is with tobacco in America, signifying a certain elasticity of the tobacco
leaves. The word ‘‘gum” in this connection is derived from the erroneous idea that
the elasticity is caused by a content of *‘ gummi elasticum” orcaoutchouc, Behrens
has recently shown that the ‘‘life” of fermented tobacco leaves is due to a greater
amount of hygroscopic moisture, caused by a higher percentage of malates of
potassa and soda.
“The resuits obtained by the firm of Schimmel & Co., in Leipzig (recently pub-
lished in Chemiker-Zeitung, 1899, No. 80), are in full accord with the writer’s obser-
vations. No nicotianine, but considerable ammonia was present in the aqueous
distillate of the sweated tobacco tested.
53
pounds, nicotine contributing in a certain measure to the formation of
these.!
It was observed by Jenkins, Behrens, Kissling, and others that a
certain amount of nicotine (one-fourth to one-third) is destroyed by
the process of sweating; hence it is natural to connect the formation of
aromatic products with the disappearance of a certain portion of the
nicotine. Cured tobacco rich in nicotine may, by a thorough sweat,
become poor in nicotine and rich in aroma, while after an insufficient
sweat it will be rich in nicotine but poor in aroma.
It is a well-known fact that a high content of nicotine in a cigar is
often associated with a poor aroma. Strong cigars are not always the
best. But all attempts to produce by partial oxidation of nicotine sub-
stances of an aroma similar to that of good cigars have thus far failed.
By moderate oxidation, as brought on by silver oxide or hydrogen
peroxide, nicotyrine and oxynicotine result, while by a more powerful
oxidation nicotic acid is formed—products which have no relation to the
odor and aroma of sweated tobacco. The writer has also applied plati-
num-black as an oxidizing agent. It was left to act for several weeks
on a 4-per-cent aqueous solution of nicotine at the ordinary temperature
as well as at about 50° C., but the desired effect was not observed,
although the nicotine became much altered. Evidently the oxidation,
caused by the oxidizing enzyms in the sweating heaps, takes a different
direction.
Recent investigations of Thoms” have shown that the flavor of the
tobacco smoke is chiefly due to an ethereal oil which is produced by dry
distillation in the process of smoking from a product of the sweat.
Twenty kilos of tobacco, smoked by an aspirator, yielded 75 grams of
this oil, which was of a stupefying odor and produced headache and
trembling of the limbs when inhaled in a concentrated state. It con-
tained, among other things, 9 grams of a phenol of creosote-like odor.
The best method of avoiding the poisonous action of the tobacco |
smoke while enjoying its beneficial stimulating effects is found with
the Turks, Arabs, and Persians. The use of a wash bottle (nafas)
before the smoke reaches the mouth removes a great deal of the poison-
ous products. Géorgiades found that each 18 grams of tobacco (a
pipe full) showed 0.947 gram nicotine, the nafas through which this
quantity of tobacco was smoked showed 0.595 gram nicotine, while the
washed smoke from same amount contained but 0.0225 gram.
INJURY TO THE AROMA.
The aroma may be injured by various causes, as, for example, by a
high content of fat or of protein in the tobacco. Certain tobaccos which
‘Opinions as to the formation of the aroma are much divided. Van Bemmelen
(Landw. Vers. Stat. 37, 388) holds that the organic acids of the leaves have a
certain influence.
*Chem.-Zeitg., 1899., No. 80.
54
have a fine odor at the ordinary temperature have but a poor aroma
when smoked, since the aromatic substances may be disguised by the
products of dry distillation of fat and protein when the cigar is smoked.
A high fat content is indeed very injurious. Other compounds also,
interfering seriously with the aroma, appear sometimes to be produced
_ under certain climatic conditions. For example, the tobacco produced
in Connecticut in the unusually wet season of 1897 was so inferior
that the sales did not pay the outlay for fertilizers.' The buyers
claimed that the cured tobacco had a *‘ stink” about it and that it also
showed a similar odor after sweating. Such injurious products seem
not infrequently to be present. It is on this account that tobacco is
subjected in certain factories to a strong current of air for twenty-four
hours at the ordinary temperature, in order to take out the “rank”
odor before it goes to the bench for cigar making. Indeed the air
which has passed through such tobacco contains a very sharp substance
which brings tears to the eyes.
The influence of climate upon the formation of certain products in
the tobacco plant may also be inferred from an observation made by
Schimmel. While 43 kilograms of tobacco from South America yielded
on distillation with water mere traces of a volatile oil, 15 kilograms of
German tobacco yielded 6 grams of a thick and dark-colored oil having
an odor similar to that of camomile. This oil contained, according to
Thoms, no terpens, but it contained among other things a small amount
ofa phenol. A further injury to the aroma is to be expected from the
treatment of the tobacco in the field with paris green and other arse-
nious preparations to destroy caterpillars. -Many tobacco growers
avoid the use of such preparations altogether and do not begrudge the
extra expense for the labor required in picking off the caterpillars by
hand. Others apply Paris green only in the young stages of the plant—
1 part well mixed with 100 parts of flour—but in certain districts,
where caterpillars occasionally become very numerous, Paris green is
applied on the ripening leaves in proportions of about one-fourth of a
pound to 40 gallons of water. In one pound of sweated tobacco from
such fields M. Peter found from a trace to 1.7 grains arsenious acid!
Such tobacco when smoked may be expected to have a disagreeable
odor, since even the smallest quantity of arsenious acid produces, in
contact with a glowing substance, a disagreeable odor resembling that
of garlic. But more serious than the injury to the aroma is the injury
to health when such poisoned tobacco is habitually smoked. An injury
to the odor of tobacco may also be caused by the development of certain
fungi on cigars kept in a too moist atmosphere. Even a putrid odor
may thus be produced, as Splendore has observed in one case.?
'On the other hand too dry seasons are just as injurions, since the tobaceo pro-
duced may refuse to sweat.
?This weuld correspond to 0.025 per cent arsenious acid or about 0.05 per cent
paris green.
511 tobacco, p. 11, 1899.
55
Numerous experiments have been made to improve the aroma of
poor tobacco. Ovxidizing media have been applied to destroy supposed
injurious by-products. The writer tested the action of a 1 per cent
solution of potassium permanganate for five minutes, but the results
were not encouraging, on account of the injury to certain other
properties.
Other methods consist in the application of substances of powerful
aroma. For example, we find among the ingredients for the preparation
of petuning liquids anise seed, cloves, cinnamon, coffee, and tincture of
valerian.! In Cuba tonka beans and vanilla beans are also used to
improve the aroma, but with very rank tobaccos even such ingredients
prove insufficient. The important question of how to improve poor
products deserves careful attention and further detailed study.
NITRITE CONTAINED IN SWEATED TOBACCO.
Although the tobacco of commerce has been the object of frequent
and numerous analyses, one compound occasionally occurring in it has
thus far been entirely overlooked. It is the nitrous acid present in the
form of nitrites. While nitrates frequently occur in various living
plants and also in fresh tobacco leaves, nitrites do not. Indeed, these
salts would act very poisonously on the living cells if they accumu-
lated to even a small degree. The writer has observed that the poison-
ous character of free nitrous acid is so great that it kills algve after one
day, even at a dilution of 1 part to 100,000 parts, although its acid
character is so weak that it is easily liberated from the nitrites by
dilute organic acids, such, for example, as are contained in the cell sap
of most plants; hence the salts of nitrous acid are also very strong
poisons wherever an acid-cell sap in the plants can liberate nitrous acid
from them.
When tobacco leaves rich in nitrates, however, are subjected to the
sweating process after being cured a portion of the nitrates is reduced,
whereby, as an intermediate step, nitrites are formed, ammonia repre-
senting the final product. Some sweated tobaccos are so rich in nitrite
that a concentrated extract, even when prepared in the cold, gives a
decided odor of nitrous acid upon the addition of sulphurie acid, and
even the smallest quantity of the extract produces at once separation of
iodine from potassium iodide on addition of a little sulphuric acid.
When upon dilution the brown coloration of the tobacco extract is
sufficiently diminished, the well-known test of Gries for nitrites is also
easily obtained. The tobacco extract containing nitrites gives a blue
reaction with tincture of guaiac, but this reaction of nitrous acid is also
obtained after boiling the extract for a minute, while the similar blue
reaction caused by oxidase is made impossible after heating the extract
a short time to 67° C. (153° F.), or, if the extract is weakly alkaline,
’ Report No. 62 (p. 17), U. S. Department of Agriculture. Marcus L, Floyd,
56
to 75° C. (167° F.). By this control test erroneous conclusions can
be avoided. ;
An accumulation of nitrites in the sweating tobacco might in the
course of some weeks attack the oxidizing enzyms at the temperature of
the fermenting heaps, thus terminating this process sooner than desir-
able. Hence nitrates should not be applied in too large quantities in
the manuring of tobacco fields, since they may give rise to the forma-
tion of nitrites in the sweating process. Bacterial action need not be
assumed in this process.
AMOUNT OF HEAT PRODUCED BY SWEATING IN BULK.
Since the loss of organic substance from the cured leaves in the sweat-
ing in bulk amounts to about 5 per cent dry matter, and the cured
leaves consist of nearly 40 per cent of carbon and 6 per cent of hydro-
gen, al approximate calculation can be made as to the amount of heat
generated by the oxidization going on in the heap. For an accurate
calculation it would be necessary to know the exact amount of carbonic
acid and water formed by the oxidation, and further, how much of the
carbonic acid was generated from previously present carboxyl groups,
and how much water was generated from previously present hydroxyl
groups; moreover, it should be known how much total ammonia is
produced in the sweat. But, on the assumption that only one-half of the
carbonic acid and one-half of the water produced are due to perfect
combustion, and that the carbon and the hydrogen in these products show
the same proportion as in the cured tobacco, we will obtain numbers
which are certainly rather an underestimation than otherwise. The
fermenting piles are made up of from 2,000 to 7,000 kilograms of
tobacco. Let us assume a pile with 2,000 kilograms of dry matter.
The 5 per cent loss after the sweat would then amount to 100 kilo-
grams. According to our assumption this would involve a complete
combustion of 20 kilograms of carbon and 3 kilograms of hydrogen.
Since one gram of carbon produces 7,678 units of heat and one gram of
hydrogen 35,808 units of heat, it follows that 20 kilograms of carbon
would yield 153,560 major calories and 3 kilograms of hydrogen 101,400
major calories. This heat would suffice to heat up 254,960 liters of
water for 1° C.
CONCLUSION. 3
Various problems relating to the manufacture of tobacco have been
touched upon in this report, some of them within easy reach of
Solution, others of a very difficult nature. The prevention of fungous
attacks in the barn or in the cases, the regulation of the temperature
and humidity in the curing process, and the proper control of the
Sweat are points that can easily be settled. In many cases the re-
placement of the stalk-curing by the single-leaf curing process may
prove a financial success. But there are other problems of a more
57
_ delicate and difficult nature, as the prevention of the mosaic or calico
“disease and the proper composition of the tobacco leaf while ripening.
Upon this composition depends the development of a desirable aroma
the sweating process. Climate and weather are here such potent
etors that human art can accomplish directly but little. Too cool
nd rainy weather may favor, for example, the production of fatty
patter, which certainly exerts an unfavorable effect upon the aroma
smoking. There may be produced, however, still other products
hich are unfavorable to the aroma. Too dry weather may also inter-
e with the proper composition of the ripening tobacco leaves. By
ossing and selection, however, varieties of tobacco may possibly be
oduced that even under unfavorable climatic conditions will not form
uch of the compounds which injure the aroma. In regard to the
slection of the seed, it may be mentioned that even now some farmers
» so far as to import their seed directly trom Cuba each year.