CIGARETTE TOBACCOS Chemical Changes That Occur during Processing The chemical compositions of the three principal types of tobaccos used in the manufacture of blended cigarettes are discussed and data that show some of the changes which occur in the chemical composition of these tobaccos during processing from the time they are harvested until they appear in the finished cigarette are presented. The operations and sequence of operations to which cigarette tobaccos are subjected from the time of harvest are discussed.
F. R. DARKIS AND E.
J. HACKNEY
Liggeff and Myers Research Laboratory, Durham, N. C.
ter flavor to the smoke; however, the total effect of the smoke may be milder or more neutral. Leaves from the top portion of the stalk add aroma and flavor to the smoke but produce a stronger smoke which may be pungent and irritating. Burley is the main air-cured tobacco used in cigarettes. The better burley cigarette tobaccos are the ripe, mature leaves produced near the base of the stalk; these are used t o some extent in most blends. They are considered to be loose-structured and light in weight, they burn well, produce a mild smoke, and fill the cigarette without increasing its weight significantly. These lightweight burley tobaccos are very absorptive and readily take up flavorings, sweetening agents, and humectants which may be part of the finished cigarette. Other burley tobaccos from the middle and top portion of the stalk are often used in cigarettes, but these also impart strength and irritating properties to the smoke and may produte a smoke which is quite pungent. It is usually such burley tobaccos that impart outstanding and characterizing notes to the finished cigarette. Maryland tobacco, one of the air-cured types, is used to a limited extent in many blended cigarettes. Its chief virtue is that it is a loose-structured tobacco that burns well and possesses filling power t o a high degree. When used alone it does not produce a pleasing smoke, but when blended with other tobaccos it is believed to improve the smoke of the blend. The better Maryland cigarette tobaccos are those produced on the lower and middle parts of the stalk. Turkish tobaccos are used primarily to impart aroma to the smoke. The most aromatic of the Turkish tobaccos are produced on the middle and top portions of the stalk, consequently these are the only ones imported for use in blended cigarettes. The Smyrna type of Turkish tobacco is aromatic and imparts a heavy, pungent but pleasing aroma to the smoke. It is used in larger volume than other Turkish types. Some Smyrna tobaccos, however, impart a bitter and lasting taste to the smoke. The Samsun and some of the Greek types of Oriental tobaccos possess aroma in lesser volume than the Smyrna tobaccos, but they burn well, producing a mild, pleasant-tasting smoke having a delicate fragrance which blends well with other components of the smoke. If these tobaccos are used in significant quantities they tend t o improve the desirable qualities of the smoke. Humectants and sweetening agents are used in practically all blends of American cigarettes; flavoring agents are used in many blends. Glycerol is considered to be the best humectant for cigarettes; it is used either alone or in combination with other humectants such as glycols, hexahydric or sugar alcohols, invert sugars, and extracts of numerous kinds of fruits. The active humectants in the fruit extract are sugars. These materials are conditioning agents and are used to prevent rapid changes in moisture content of the cigarette. Vari-
URING the past fifty years the use of blended cigarettes by the American public has progressively increased from one billion cigarettes to over 350 billion per year (5). The American-made blended cigarette has been accepted with favor ill all sections of the world, and in most of those countries where it has been offered for sale without restrictions, it has replaced most other cigarettes. Blended cigarettes are made from three main types of tobacco. These in order of importance are: Heat-cured tobaccos, normally spoken of as flue-cured, bright, or Virginia tobaccos; air-cured tobaccos, known as burley or Kentucky and Maryland tobaccos; and sun-cured or Turkish or Oriental tobaccos. Each of these three types is of the species known as Xicotiana tabacum L., belonging to the family Solanaceae, and each contains varying amounts of the alkaloid nicotine that characterizes the species. Many of the basic chemical constituents, other than nicotine, found in the green vegetative tobacco leaf are not significantly different from those found in tissues of other green plants. Because of the variety of tobacco, differences in soils, extent and manner of fertilization, variations in climate, cultural practices, and differingage and position of the leaf on the stalk the chemical coinposition of the green tobacco varies over a wide range, This variation is manifest also in the product of commerce. The chemical changes that take place during the processes of curing and aging of each of the three types of cigarette tobaccos are somewh:Lt similar. The extent to which these changes take place, however, varies with the method of curing and the duration of and temperatures a t which aging is permitted to take place. Further clieniic~nlchanges take place, but, to a limited extent, in the handling of cigarette tobaccos. The chemical constituents of the tobacco leaf tissue consist in large part of organic substances such as organic acids, alkaloids, organic bases, carbohydrates, nitrogenous constituents, and resins. These materials characterize the kinds of tobacco and undergo transformations and changes during the processing of the leaf from the time it is harvested to the time it appears in the blended cigarette. This paper is concerned with the changes of a chemical nature that occur in these groups of organic constituents in the tissue of the tobacco leaf during this period.
D
Tobaccos Used in Blends Flue-cured tobacco of good cigarette grade from the lower and middle portion of the plant is the basic component of most blended cigarettes, This tobacco furnishes most of the pleasing part of the aroma of tobacco in the cigarette and imparts aroma and a large part of the pleasing taste factors to the smoke of the cigarette. Lower grades of flue-cured tobacco from the base and top portions of the stalk are used in some blends. Leaves from the lower portion of the stalk may impart a woody, earthy, and bit-
284
ous sugars and fruit extracts are added t o the blended tobaccos to impart a sweet taste to the cigarette and t o the cigarette smoke. Aromatic substances, which increase the aroma of the blend and impart different notes to the flavor and aroma of the smoke, are usually dissolved in alcohol or alcoholic materials such as rum; the solution is then sprayed on the blended tobaccos. Coumarin, vanillin, rum,brandy, fermented wines, honey, balsam of Peru, balsam of tolu, geraniol, oil of cloves, oil of cinnamon, and oil of peppermint have been used as additives. Tobaccos of different typesand varying chemical composition are selected inproper proportions to produce a blend that is essentially constant in chemical composition year after year. The variation in the proportion of the main types of tobaccos used in Americanmade blended cigarettes is rather extensive; Table I gives an idea of t h e breadth of this variation.
Table 1.
285
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
February 1952
Variation in Proportion of Tobaccos Used in Blends
Type of Tobacco Flue-cured or bright Burley Maryland Smyrna (Turkish) Samsun and Greek (Turkish)
Maximum Content, %
Minimum Content, %
75 45 5 8 5
45 15 1 5
0
Methods of Analysis The methods of analysis used in this work were reported in a previous publication (10). The data are expressed on a moisture-free basis and except for acids and hydrogen ion concentration are given in percentage of moisture-free tobacco. The acids are expressed in milliliters of 0.1 N alkali required to neutralize the acid in 1 gram of moisture-free tobacco. The hydrogen ion concentration is expressed as pH and the averages of pH were obtained by converting these values t o moles of hydrogen ions per liter, averaging these values, and reconverting the averaged values t o pH units. All samples in preparation for analysis were ground in a Wiley mill t o pass through a 1-mm, sieve.
Composition of Cigarette Tobaccos Tobaccos of each of the main types used in cigarettes vary over a wide range in chemical composition. Table I1 shows the extent of variation for certain organic constituents and groups of organic constituents. These data indicate (1) that the flue-cured tobaccos are characterized by high sugar content, low t o medium content of nitrogenous and acid constituents, and medium content of nicotine; (2) that the Burley tobaccos are characterized by low content of carbohydrate material and high content of nitrogenous materials, nonvolatile acids, and nicotine (the reaction of these tobaccos, however, is not as acid as that of the flue-cured tobac-
cos); (3) that the Maryland tobaccos are characterized by low content of carbohydrates and nicotine and medium content of nitrogenous constituents and nonvolatile acids; (4) that the Turkish tobaccos as a whole are characterized by low content of nicotine and low pH or high acid reaction; they are low to medium in content of nitrogenous-and Carbohydrate materials and xnediuni to high in content of nonvolatile acids.
It was pointed out in revious papers (7-9)that such factors as changing weather con&ions, soil type, fertilization, and stalk position contribute t o the wide variation in content of chemical constituents found in fluecured tobaccos. In respect to stalk position it was shown (8) that nitrogenous constituents and nicotine were most abundant in leaves from near the top of the stalks and least abundant in those on the md-portion and lower part of the stalk. It also was shown that the soluble sugars were a t a maximum in leaves produced near the middle of t h e stalk and that the decreased in content as the leaves approached both the base a d t h e top of the stalk. The nonvolatile acids were found to be the reverse of the sugars, being at a minimum in leaves produced near the middle of the stalk, increasing in content in leaves near the ends of the stalk, being maximum in content in leaves near the base of the stalk. As measured by H, the more acid tobaccos were produced near the top of the s t a g . I n connection with our work on tobaccos, in general, samples of Burley and Mar land tobacco representing the cured leaf from the base, the midrdle, and the top parts of the stalk were collected from farms distributed over most of the area in which Burley and Maryland tobaccos are grown. These samples were obtained from the growers before the period of marketing Legan: burley samples were obtained from 406 farms (109 in 1947,64 in 1948, and 233 in 1950); Maryland samples were obtained from 82 farms (42from the 1949 cro and 40 from the 1950 crop). Each of these samples was analyzei' for certain organic constituents. The averaged analyses for the three burley and the two Maryland crops are given in Table 111. These data indicate that total nitrogen, prdtein nitrogen, and soluble acidity increase in the leaves from the base t o the top of the stalk. These data also indicate that the content of nicotine and of petroleum ether extractive is greatest in those tobaccos from the middle of the stalk and least in those from the base of the stalk.
Curing Cigarette Tobaccos Significant chemical and physical changes occur in tobaccos while they are undergoing either the process of flue curing or the process of air curing. Numerous data on the nature and magnitude of these changes are presented and discussed in the literature (3, 4 , 16-18, $0,21, 26,27, 28,W, 34, 86). Theliterature, however, does not contain data pertaining t o t h e chemical changes which occur during the sun curing of tobaccos of the Turkish type. The culture, handling, and curing (usually 7 t o 15 days) of suncured tobaccos are discussed in detail elsewhere (11). The chemical changes which take place during sun curing consist primarily in the loss of starch with concomitant formation of soluble sugars -
Table 11.
Chemical Constituent Total.nitTogen. % Protein mtroaen. 5%
Min. 1.00 0.40
Approximate Chemical Composition of Tobaccos Now Being Used in Blended Cigarettes Flue-Cureda In better Max. toEt%s Min. 3.00 1.30
1.80 0.70
1.50 0.50
Burleye In better Max. 4.50 2.40
toft&*
2.75 1.25
0.170 0.080 0.450 0.100 0.500 0.275 l0 3.50 Nicotine, % 0.40 4.50 2.75 1.75 0.80 Petroleum ether 3.00 7.50 5.25 2.50 6.00 4.75 extract % 3.50 1.75 8.00 Starch sl', 0.50 3.00 1.60 6.00 32.00 10.00 Solubl; sugars % 0.10 1.50 0.40 Nonvol. acids: ml. 0.1 N alkali 9.00 26.00 14.00 15.00 38.00 26.00 Water-sol. acids, ml. 2.60 0.1 N alkali 0.30 5.00 3.45 3.50 1.50 5.70 5.20 5.20 7.50 6.50 4.40 PH a Samples for analyses were unstemmed leaf purchased since 1945. b Samples for analyses were unstemmed leaf purchased since 1937.
Marylanda
In better Min.
Smyrna b In better Max. tobaccos grade
Min.
Max.
tobaccos grade
1.25 0.70
3.00 1.50
2.00 1.10
1.40 0.75
2.00 1.00
0.080 0.65
0.360 2.00
0.160 1.35
0.100 0.50
0.160 1.30
3.50 1.00 0.50
6 50 3.50 1.50
4.70 2.00 0.90
3.50 4.00 12.00
7.00 10.00 19.00
13.00
25.00
18.00
16.00
0.40 5.30
3.50 7.00
1.50 6.26
...
4.90
Samsunb
In better
Min.
Max.
1.65 0.85
2.50 1.00
3.50 1.30
2.85 1.05
0.125 0.95
0.300 0.70
0.640 1.90
0.390 1.30
5.50 6.50 15.00
3.90 1.90 3.00
6.50 4.00 7.60
5.50 2.80 5.50
23.00
18.50
21.00
27.00
23.50
...
...
... 4.75
... 5.15
4.90
5.25
5.05
f
b%accos rade
...
286
INDUSTRIAL AND ENGINEERING CHEMISTRY Table 111.
Composition of Air-Cured Tobaccos from Different Stalk Positions
Chemical Constituent Total nitrogen, % Protein nitrogen, % a-Amino nitrogen, yo Nicotine, % Petroleum ether extract, % Starch, % Nonvol. acids.,.ml. 0.1 N alkali Water-sol. acids, ml. 0.1 N alkali PH
Burley, Stalk Position Lower Middle Tpp third third thud 3.04 3.37 3.83 1.33 1.13 1.14 0.246 0.604 0.394 2.60 2.02 2.69 4.26 4.50 4.71 1.34 1.36 1.41 28.54 27.32 24.61 2.06 3.04 3.62 6.40 6.17 5.95
and the formation of soluble nitrogenous constituents a t the expense of insoluble nitrogenous materials. The works of Hobbs and Layton (19) and Moffett (Sd),each working with Americangrown tobaccos of the Turkish type, show a decrease in starch and protein nitrogen accompanied by an increase in soluble sugars and soluble nitrogen during curing. The data obtained by Hobbs and Moffett are presented in Table IV. Each of these investigators analyzed the tobacco several months after the end of curing. The data indicate that only slight changes occurred after 14days or after the end of curing.
Redrying of Cigarette Tobacco I n most areas the farmer prepares the flue-cured, the burley, and the Maryland tobacco for sale by first separating the leaves into grades, each of which is tied into small bunches called hands. These hands of tobacco are arranged neatly in piles on baskets. The baskets are placed on the warehouse floor and the tobacco is sold a t auction t o the highest bidder. To grade the tobacco and to have it moist enough that the farmer can transport it to market without causing breakage may require as much as 25% water in the tobacco. As the tobacco comes into possession of r e p resentatives of the domestic cigarette industry or of export dealers, it may contain anywhere from 10 to 25% water. To bring the tobacco t o a relatively uniform moisture content and to have the moisture a t such a level that the tobacco will undergo aging, and, a t the same time not deteriorate owing t o the action of fungi and molds, the purchaser subjects the tobacco to a process known as redrying. I n this process the tobacco is dried by means of heat t o a level of moisture considerably below that at which it is to be stored. It is then cooled, and moisture in the form of steam is added until the tobacco is a t the desired moisture content. This process is carried out in tobacco redrying machines which are modified textile dryers (la). The dryers consist of three drying sections, one cooling section, and one reordering section (see diagram, page 283). Tobacco is usually redried either in the form of hands or in the form of strip-that part of the leaf from which the midribs have been removed. The hands of tobacco are sus ended on sticks and moved slowly through the five sections of tEe dryer. The temeratures used and the time required to move the hands of togacco through the dryer may vary considerably from one redrying plant to another. The following schedule is not far from the average conditions: First drying stage, 70" to 77" C. for 8 to 10 minutes; second drying stage, 100"to 105" C. for 8 to 10 minutes; third drying stage, 90" C. for 8 to 10 minutes; and cooling chamber for 8 to 10 minutes. Here the temperature drops from 90" C. to somewhat above the prevailing atmospheric temperature. In the reordering chamber the tobacco is exposed to low pressure steam for 12 to 15 minutes and attains a temperature of 50" to 55O C. and adsorbs moisture. Strip tobacco is spread on an apron to be conveyed through the dryer which is operated at approximately the following conditions: First drying stage, 65" to 70" C. for 1.5 to 2 minutes; .second drying stage, 70" to 85" C. for 1.5 to 2 minutes; third drying stage, 55" t o 62" C. for 1.5 to 2 minutes; and cooling chamber for 2 to 2.5 minutes. The temperature drops from 62" C. to somewhat above the prevailing atmospheric temperature. In the reordering chamber the tobacco is subjected to low pressure steam for 3 t o 4 minutes and attains a temperature of 45" to 55" C. When tobacco leaves the redrying machines, the flue-cured tobacco usually contains from 9
Maryland, Stalk Position Lower Middle Top third third third 1.79 2.15 2.96 1.02 1.12 1.50 0.127 0.367 0.182 1.10 1.63 1.68 4.93 3.65 5.19 17.59 0.98 6.53
17.95 1.73 6.14
16.08 2.07 5.80
Vol. 44, No. 2
to 11yomoisture, and the burley tobaccocontainsfrom 10to 12% moisture. Experience has shown that these tobaccos age satisfactorily a t these contents of moisture. On leaving the dryer the tobaccos are prized into hogsheads, which usually contain from 900 to 1000 pounds each. T h e hogsheads a r e stored under the prevailing storage t e m p e r a t u r e w h i c h fluctuates with the seasons.
The redrying process as a method of treating tobaccos has been used for many years. The chemical changes, if any, occuring in the tobaccos as a result of redrying seem not to be referred to in the literature. Kingsbury and coworkers (92) studied methods of recovering the nicotine in the exhaust gases from the redryers. They state that flue-cured tobacco possessing an initial content of 2 to 3% nicotine lose about 0.18% of the dry weight of the tobacco as nicotine. Kingsbury does not state whether he was studying gases from a dryer which was redrying tobacco in the form of the leaf or the strip. However, it is probable that the tobacco being redryed was in the form of the leaf. I n order to obtain information pertaining to the possible chemical changes resulting from redrying, 82 samples of burley tobacco collected from most of the sections of the burley area of the 1949 crop and 32 samples of flue-cured tobaccos of the Georgia type of the 1951 crop in the form of strips were sampled on entering and again on leaving the dryers. Chemical analyses of these samples (average results) are given in Table V. The data in Table V indicate that the magnitude of change in the chemical constituents studied is small. Slight losses in total' nitrogen, amino nitrogen, and nicotine occur. Probably the decrease in nicotine resulted from small losses in free nicotine carried off with the water vapor from the tobacco. Free nicotine is
Table IV.
Changes Occurring in Sun-Cured Tobaccos during Curing
Days before Analyses Were Made 0 5 14 117 Smyrna Tobacco (19) Starch % 31.20 6.90 5.20 5.13 Solubl;! sugars, % 2.28 26.60 19.20 18.61 Insoluble nitrogen, % 1.24 0.96 0.97 0.99 voluble nitrogen, % 0.20 0.59 0.61 0.53 Total nitrogen, % 1.44 1.55 1.58 1.52 0 End of curing 130 Samsun Tobacco (24 Total nitrogen, % 2.53 2.41 2.39 Protein nitrogen, % 1.53 1.10 1.09 Soluble nitrogen, % 0.85 1.20 1.18 a-Amino nitrogen, yo 0.201 0.464 0.447 Nicotine Yo 1.47 0.91 0.85 Petroleuh ether extract, % 6.56 5.90 6.01 Starch, % 6.58 2.55 2.49 Soluble sugars 7 5.58 2.48 2.47 Nonvol. acids,'m?. 0.1 N alkali 14.28 15.56 14.59 PH 4.99 4.86 4.84 Chemical Constituent
Table V.
Changes Occurring during the Redrying of HeatCured and Burley Strips
Flue-Cured Strips (1951 Crop) Aftqr Before redrying redrying 1.92 1.88 0.70 0.70 0.237 0.227 2.52 2.45 16.72 16.85 Reducing &gars, % 15.17 15.77 Nonvol. acids, ml. 0.1 N alkali 3.50 Water-sol. acids, ml. 0.1 N alkali 3.50 5.22 5.21 PH Chemical Constituent Total nitrogen, % Protein nitrogen, % Nicotine. nitrogen, a-Amino 7" %
Burley Strips (1949 Crop) 'Before After redrying redrying 3.33 3.27 1.55 1.55 0.296 0.281 2.58 2.48
....
25.84 1.92 6.29
....
25.64 1.85 6.32
(I February 1952
INDUSTRIAL A N D ENGINEERING CHEMISTRY
readily distillable with steam. The losses in nicotine reported are less than those reported by Kingsbury (22). This may be due to the possibility that Kingsbury was redrying leaf tobacco which remains in the dryer longer and usually is heated t o a higher temperature than are the strips.
Aging Cigarette Tobaccos Cigarette tobaccos whether heat cured, sun cured, or air cured are not best suited for consumption .in the form of cigarettes‘immediately after curing and redrying. Such unaged tobaccos, when smelled, impart an irritating, pungent, and unpleasant sensation to the membranes lining the respiratory passages. They lack the aroma of aged tobaccos and smell similar t o many types of freshly dryed plant tissues. They are often referred to as being “raw,” “green,” “rough,” “strong,” “immature,” or “unaged.” Most tobaccos if subjected t o the process of aging undergo detectr able changes in color, aroma, and taste. These changes are associated with and result from numerous chemical changes which take place during aging. Such changes are not well understood, and but few pertinent data are available in the !iterature. The aging of cigarette tobaccos should not be confused with the fermentation of cigar tobaccos (IS, IS), which has received much study, However, there is a lack of agreement among the investigators regarding the mechanisms which take place during fermentation and the causative agents which bxing them about. Most aged cigarette tobaccos, especially the heat-cured and sun-cured ones, are aromatic and possess a fragrance which is quite pleasing. It is not known if the enhancement of the a r e matic properties is due t o the elaboration of aromatic constituents during aging OF to the loss of volatile irritating constituents which may hide the presence of and mask the effect of the fragrance from the unaged tobaccos. At present, use of the senses of smell, taste, and sight is the best means of determining the completeness of the aging of cigarette tobaccos. Aging is accomplished either by allowing the tobacco (moisture content 8.5 to 12.5y0) to undergo natural aging for 18 or more months under storage conditions which follow seasonal fluctuations, wherein the tobacco temperature may vary from 0” to30° C., or by “forced sweating,” which, in general, consists of raising the temperature of the mass of tobacco in a hogshead in an atmosphere of such relative humidity that the moisture content of the tobacco will not change appreciably. The latter process has been used extensively in the cigarette manufacturing industry t o hasten the aging of new tobaccos and t o improve these tobaccos t o the extent that they can be used in cigarette manufacture before the passage of sufficient time to allow them to age naturally. Apparently the sweating of cigarette tobaccos has not been discussed in the literature and data pertaining t o the chemical changes taking place during forced sweating are not available. Dixon and collaborators ( l a ) made an extensive study of aging for heat-cured tobaccos and describe the process in much detail as well as the physical changes which the tobacco undergoes. Their data show that the major part of the change in the chemical constituents takes place within the first 12 months after the tobacco has been prized into the hogshead and that essentially no change takes place between 24 and 30 months after prizing. The analyses show that significant losses occur in amino nitrogen, soluble sugars, and nicotine. They also show that the reaction of the tobacco, as measured by pH, becomes more acid which indicates either an increase in soluble acids or a loss of soluble materials of an alkaline nature. Frankenburg (IS) postulates that the change in pH is due t o the formation of volatile organic acids. Dixon and coworkers suggest that the loss in soluble sugars and amino nitrogen may be explained by the Maillard reaction (23)that is, a reaction taking place between the amino acids and sugars t o yield highly colored aromatic products known as melanoids @‘,I$, 80). Frankenburg (IS),however, suggests that the decrease in amino compounds may be explained by formation of
287
complexes with phenoliclike compounds which w e present in the tobacco (SI). The data of Dixon and coworkers (12)also show an increase in the moisture content of the tobacco during aging; they indicate that this is due to “reaction water,” generated by chemical reactions which take place within the tobacco tissue. Dixon and coworkers ( I @ found only small numbers of micro-organisms and small amounts of enzymes present in heatcured tobaccos. They also found that only insignificant quantities of carbon dioxide were present in the mass of aging tobacco, and they failed t o find evidence of self-heating in the tobacco during natural aging. They state that the loss in dry weight of the tobacco is less than 2.5%. They believe their findings indicate that the natural aging of heat-cured cigarette tobaccos is the result of strictly chemical processes. The literature seems to contain no reference t o chemical studies on the natural aging of burley and Maryland tobaccos. However Woolford (35) obtained data on the natural aging of Americangrown tobaccos of the Turkish type. The composite of Woolford’s results for tobacco of the Smyrna variety of the 1942 and 1943 crops is presented in Table VI. Table VI.
Changes Occurring during the Natural Aging ’of Turkish Tobaccos
Chemical Constituent Total nitrogen, To Protein nitrogen, % a-Amino nitrogen, Yo Nicotine % Petroleuk ether extract, % Starch, yo Soluble sugars, % PH
Before Aging 2.01 0.95 0.217 1.00 6.79 5.18 11.03 4.40
At End of 1 Year 1.93 0.93 0.156 0.92 6.50 4.43 9.03 4.37
At End of 2 Years 1.91 0.92 0.146 0.86 6.33 4.38 8.78 4.31
Turkish tobaccos are accepted from the grower in loose bales or packages. After “manipulation” (96) which consists of sorting, grading, and baling the tobacco in the preferred manner, the compact bales are placed in storage houses to undergo natural aging. The moisture content of the tobacco in the bales is usually in the neighborhood of 10 to 12y0, and each bale usually contains from 70 to 125 pounds depending on the type of tobacco and method of baling (26). I n storage the bales are usually piled three or four deep, and the position of the bale in respect t o the bottom and top of the pile is changed periodically; also, the up and down sides of the bales are reversed as their position in the pile is changed. The tobacco used by Woolford (65) for his studies was baled in February in Tongas bales (26). The bales varied in weight from 80 to 100 pounds. I n storage they were piled three deep and were turned and changed in position in the pile once each week. Thermometers were placed in the bales to indicate the temperature. Samples were taken from each bale in March immediately following the baling of the tobacco and during the last week of the October which followed each of the two succeeding summers. Active periods of aging (as evidenced by increased pliability of the leaf and more pronounced aroma) in Turkish tobaccos usually begin with the oncoming of warm weather and proceed for several months. They may, however, fail to continue for the duration of the period of warm weather. When the aging of Turkish tobaccos becomes less active the tobaccos are said t o be “drying off.” Persons who have been associated with the purchasing, manipulation, and importing of tobaccos grown in Turkey and Greece may state that those tobaccos undergo increases of 10” C. or more in temperature during aging. Wool ford (36),however, observed increases in temperature Rf only about 2” C. above the ambient temperature. He did observe a considerable softening and pliability of the tobacco and an evolution of a pleasing fragrance as well as a characteristic rancid and acidic type of odor. This rancid and acidic odor was less pronounced during the second summer of aging.
288
INDUSTRIAL AND ENGINEERING CHEMISTRY
The data in Table VI indicate that the chemical changes found in the natural aging of sun-cured tobaccos are quite like those which occur in heat-cured tobaccos and that the aging is much more pronounced during the first year than during the second year of storage. The acidity, as measured by pH, was much greater in the sun-cured tobaccos with which Woolford (56) worked than in the heat-cured tobaccos which Dixon ( I d )used, and the change in pH which Woolford found was not as pronounced. Agreater change, however, was noted during the second year than during the first one. Woolford's figures also indicate that a loss in starch content and petroleum ether extractive occurs during the period of aging, woolford states that the aging of sun-cured tobaccos is probably due to chemical processes, but he offered no explanation of the mechanisms involved. He gives no data on the losses in dry weight of the tobacco. 15-
$1
.-
W
I
TOBACCO
I
ROOM
W Q
2 5
Iw
6
1
I
IO
I
I
20
I
I. 30
TIME IN DAYS
Figure 1. Temperatures during Forced Aging of Medium Grade Flue-Cured Cigarette Tobacco
A total of 120 hogsheads of flue-cured tobaccos of the 1949 crop were subjected to .the process of forced sweating to determine if (1) the various types and grades (7) of heat-cured tobacco responded differently t o the process of forced sweating; (2) if a period of cooling and reheating significantly improved the aging; and (3) if the aging process continued after forced sweating was discontinued: The tobaccos used were strips of the 1949 crop, from each of the flue-cured areas and represented a wide range of grades of cigarette tobaccos. On February 5 after the tobacco in the hogsheads had been examined and sampled for analysis, the temperature of the tobacco averaged a proximately 16.6' C.; the hogsheads were laced in the sweatiouse and the temperature of the house raisecfto 37.8' C. in a period of 48 hours; the relative humidity was raised to 75%. These conditions were maintained for 35 days as closely as the operating equipment permitted. It required 15 days for the temperature of the tobacco to reach 37.8" C., after which it continued to rise slightly. The maximum rise in temperature above the room temperature for different hogs-heads varied from 1.7"to 3.4" C. At the end of the 35 days, the temperature of the sweathouse was dropped to between 15.5' and 21" C. and was maintained a t this level for 15 days. During this period the average temperature of the tobacco dropped to 20" C., and the tobacco was sampled for chemical analysis. The temperature of the house was then raised to 37.8' C. in 48 hours and maintained a t this level for 20 days. The relative humidity was maintained a t 75% during this time. It required between 13 and 14 days for the tobacco tem erature to reach 37.8" C. At the end of the 20 days the geat was discontinued and the tobacco allowed to cool down. Samples were taken for chemical analysis at the end of the first 5 days of the cooling period. Dixon ( I d ) failed to observe any increase in temperature of the tobacco due to self-heating during the natural aging process; however he was working with tobaccos a t temperatures of 26" or less instead of 37.8' C. The increase of 12" C. or more in the am-
Vol. 44, No. 2
bient temperature of the tobacco during the forced sweating probably speeded up the aging process to the point where heat was generated rapidly enough to be observed as a rise in the temperature of the tobacco above that of the sweathouse. The average of the data obtained during this study is presented in Table VII. Data on changes in dry weight were not obtained.
Table VII.
Changes Occurring during the Forced Sweating
of Flue-Cured Tobaccos at 37.8' C. Chemical Before Constituent sweating Total nitrogen % 2.05 a-Amino nitroLen, % 0.177 2.42 Nicotine, % Soluble sugars, % 18.70 Petroleum ether extract, 7.01 Water-sol. acids, ml. 0.1A l k a l i, 4.35 4.99 RIHoisture, % 8.27
Period of Sampling Endof End of first second heating heating period period 2.02 2.01 0.146 0.153 2.30 2.29 17.71 17.46 7.14 7.16 4.74 4.75 4.83 4.83 9.41 9.21
2 Months after end of sweating 1.98 0.142 2.25 17.39 7.17 4.76 4.81 9.39
The data in Table VI1 when contrasted with the results of Dixon and coworkers (15')indicate that tobaccos undergo acceler ated chemical change if the temperature of the tobaccos is raised; this change was more rapid during the first 35 days a t 37.8" C. than it was during the next 20 days. Also they tend to show that the tobacco changed very little during the first 2 months in storage immediately following the end of forced sweating. Although the magnitude of the change varied somewhat from hogshead to hogshead, no single type or grade showed changes that varied significantly from the average given in Table VII. At the end of the process of forced sweating the tobaccos were darker in color, less irritating to the nasal passages, possessed more aroma and fragrance, and produced a much more pleasing smoke than tobaccos of similar age which had not been sweated. The chemical changes induced as a result of the second heating are not great, and they fail to indicate that the tobacco improved to a significant extent as a result of this treatment, These experiments gave evidence that heat was one of the predominant factors in bringing ?bout the improvement which the tobacco exhibited as a result of forced sweating. Twelve hogsheads of tobacco of the 1950 crop were force sweated a t 48.9" C. in order to determine the effect of higher temperature and to determine the amount of heat that flue-cured tobacco would stand without self-heating to the extent of causing damage. The hogsheads of tobacco (temperature, 29.4' C.) were placed in a chamber in which the temperature and relative humidity were automatically controlled within 1" of 48.9 C. and 1 % ' of 65. Thermometers were so placed as to extend to the center of the mass of tobacco in each hogshead. The average of the temperature of the tobacco in the interior of each hogshead (Figure 1) shows that the temperature of the tobacco rose to 48.9" C. in approximately 9 days and to 63.3' C. during the next 7 days. At that time the temperature of the room was lowered to 7.2" C. and was held there (7 days) until the tobacco temperature dropped to 32.2" C. Then the hogsheads were removed from the chamber, sampled for chemical analyses, and examined for changes of a physical nature. The temperature of the room was lowered when the tobacco attained a tcmperature of 63.3' C. because many flue-cured tobaccos will not tolerate a temperature of 65.5" C. for any prolonged period without undergoing serious damage. O
On examination the tobacco in these twelve hogsheads was found to have darkened considerably in color, and had the appearance of well-aged tobacco; it was essentially without irritatidn to the nasal passages, possessed a high volume of aroma, and the fragrance was light, aromatic, slightly spicy, and somewhat winelike. Experienced and competent judges of tobacco stated that it possessed the characteristics of well-aged flue-cured tobaccos. Table VI11 gives the averages of the chemical data obtained on these tobaccos, Losses in sugars and amino nitrogen occurred as in natural aging and forced sweating a t 37.8" C., but the de-
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
creases in this instance were considerably greater; one third of the amino nitrogen and 12% of the sugars as such disappeared. The water-soluble acids increased and moisture content increased, as happened in the previous studies. I n the natural aging of both flue-cured and Turkish tobaccos, significant los2es in total nitrogen and nicotine occurred. I n the study on forced sweating, the loss in total nitrogen and nicotine was less and in this study, where the temperature of the tobacco rose t o 63.3' C., it was the least. The slight loss in nicotine can account for most of the small loss in total nitrogen. The main difference, however, is the increase in insoluble nitrogen and starch, as determined by the methods used. The loss in dry weight of the tobacco in each hogshead averaged less than 1 %. The increase in insoluble nitrogen has not been detected in previous studies on flue-cured tobaccos at temperatures as high as 37.8' C. However they have been reported (14) for the fermentation of cigar tobaccos, and the formation of insoluble nitrogenous constituents has been found in the aging of burley tobaccos a t 49.4' C.
289
greater extent during forced sweating in burley tobaccos and that the decrease in amino nitrogen is less. The decreases in total nitrogen and nicotine in the burley tobaccos are small. The source of the nitrogen which was used to form the increased 13-
---. ROOM b-
MEDIUM GRADE
0-
HIGH GRADE
R
I
ROOM
MEDIUM GRADE 0
HIGH GRADE
70
Table VIII. Changes Occurring during Forced Sweating of Flue-Cured Tobacco at 37.8' C. and 65% Relative Humidity Chemical Constituents Total nitrogen yo Protein nitrogln % a-Amino nitrogin, % Nicotine, % Petroleum ether extract, % Soluble augars, % Starch, % Nonvol. acids, ml. 0 1 N alkali Water-sol. acids, ml. 0.1 N alkali KHoisture, %
Before Sweating 1.80 0.73 0.169 2.05 5.71 19.02 4.15 12.88 3.65 5.03 8.46
After Sweating 1.78 0.77 0.113 1.96 5.70 16.73 4.58 12.83 4.37 4.76 9.89
Burley tobaccos are often kept in storage for longer periods of time than flue-cured tobaccos t o allow them t o improve or age. Many burley tobaccos also fail to show the degree of aging exhibited by flue-cured tobaccos. In order to determine if sweating at higher temperatures would accelerate the aging of burley tobaccos, six hogsheads of each of a medium grade and a high grade of burley tobacco of the 1950 crop, in the form of strips, were subjected t o forced sweating a t 41.1' C., and another six hogsheads of each grade were sweated at 49.4' C. for 35 days at 65% relative humidity. The tobaccos were sweated in the well-insulated chamber described previously, and the temperatur'es in the interior of the tobacco mass were recorded daily. Samples for chemical analysis were taken before the tobacco was placed in the chamber and when it had cooled to 32.2' C. after removal from the chamber. The temperature data (Figure 2) show that the rate of rise in temperature of the tobacco is faster a t the higher room temperature and that the rise in temperature of the tobacco above that of the mom is slightly greater a t the higher room temperature. They indicate rather clearly that self-heating occurs in the burley tobaccos but to ri lesser extent than that observed in flue-cured tobaccos. The higher grade also showed slightly more selfheating than the medium grade. At 41.1' C. each of the grades remained essentially a t a constant temperature for the last 10 days in the chamber. At 49.4' C.,however, the temperature of the higher grade was receding near the end of the period during which the tobacco was in the chamber. The chemical changes which occurred in the tobaccos at these elevated temperatures were similar and of the same order of magnitude for the tobaccos of each grade. Therefore, the data for the high grade only are presented in Table IX. I n general Table IX indicates that the chemical constituents in burley tobacco do not change t o the same degree during forced sweating as those in flue-cured tobacco. The data, however, show that the insoluble nitrogenous constituents increase to a
TIME IN DAYS
Figure 2.
TIME IN DAYS
Tobacco Temperatures during Forced Aging of Two Grades of Burley Cigarette Tobacco
amount of insoluble nitrogen is not evident from the data at hand. The increase in water-soluble acid constituents and insoluble nitrogenous constituents is greater in those burley tobaccos which were sweated at the higher temperature. The average loss in dry weight of these burley tobaccos during the heating to 41.1' and 49.4' C.was approximately 0.5%. The physical inspection of the tobaccos after the sweating indicates that those which were sweated a t 41.1' C. had improved t o a moderate extent; they had lost some of the properties of unaged tobaccos, but they were still irritating when smelled and were judged t o be too new or unaged for use in cigarettes. The tobaccos sweated at 49.4' C. were judged to be well-aged; the color had become darker and duller, they had developed considerable aroma and a mintlike fragrance, and the irritation t o the nasal passages was reduced t o a relatively low level. Table IX. Changes Occurring during the Sweating of High Grade Burley Tobacco at Elevated Temperatures Temp., 41.1' C. Chemical Before Aftqr Constituent sweating sweating Total nitrogen, % 2.94 2.90 Protein nitrogen, 1.39 1.41 a-Amino nitrogen, 0.247 0.219 Nicotine, % 2.40 2.30 Petroleum ether extract, % 5.62 5.33 Starch % 1 84 1.48 Nonvd. acids, ml. 0.1 N alkali .25:25 24.65 Water-sol. acids, ml. 0.1 N alkali 1.70 1.76 6.51 6.49 Eisture, % 11.26 11 i8
%
Temp., 49.4O C. Before After sweating sweating 3.01 2.96 1.44 1.51 0.225 0.200 2.57 2.27 5.59 5 56 1.43 1.09 24.05 23.17 1.81 2.03 6.44 6.27 12.26 11.79
The chemical reactions which are responsible for the formation of insoluble nitrogenous components in flue-cured tobaccos may be different in nature from those responsible for the formation of these components in burley tobacco. Frankenburg (14) suggests that during fermentation the tannins of the air-cured leaf form complex nitrogen-containing products with some of the watersoluble nitrogenous components of the leaf tissue. No attempt was made in this work t o identify the soluble nitrogenous compounds in the burley tobaccos; the figure given for amino nitrogen is primarily a measure of nitrogen in the form of primary
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 44, No. 2
sections of the areas in which these tobaccos are grown. The data in Table X indicate Flue-cured 1948 Maryland 1948 Burley 1949 (262samples) (32samples) (72 samples) that the midrib part of both Strip Stems Chemical Strip Stems Strip Stems the air-cured and heat-cured (lamina) (midribs) (lamina) (midribs) (lamina) (midribs) Constituent types of cigarette tobaccos is 1.99 1.46 2.26 1.08 3.26 1.97 TotaL nitrogen, yo 1.24 0.62 0.77 0.42 1.49 0.65 Protein nitrogen, yo lower in content of petroleum 0.193 0.103 0.179 0.163 0.254 0.119 a-Amino nitrogen, % 0.46 1.23 0.26 2.30 0.55 2.67 Nicotine % ether extractive, nitrogenous 5.64 0.98 0.84 Petroleuh ether extract, % 6.96 1.11 6.38 constituents, and nicotine than .... .... .... .... Sol. sugars, Yo 17.98 17.21 4.35 2.05 .... .... .... Starch 7' is the strip part. 14.00 16.45 16.79 17.97 Nonvdl. acidsa 26 '65 23.84 1 .80 0.81 Water-sol. acids" 4.15 3.88 1.82 0.29 The various strips are com5.03 5.12 6.02 6.58 6.35 7.60 PH bined or made into a blend a M1. 0.1 N alkali per gram 01 tobacco. before they are fabricated into the c i g a r e t t e s a n d u s u a l l y after the tobaccos have been amines as determined by the Van Slyke Method (33). The aged. In order t o have the strips sufficiently pliable to be handled without undue breakage during the blending operaanalyses indicate that in the burley tobaccos the decrease in amino nitrogen is much too small to account for the increase in tions they need to be warm and moist. In the major part of the present day cigarette industry moisture and heat are inprotein or insoluble nitrogen. I n the flue-cured tobaccos, howcorporated into the tobacco by the thermovacuum process, which ever, the decrease in amino nitrogen is more than sufficient to consists of evacuating the tobacco, usually in multiple lots of account for the increase observed in insoluble nitrogen. Howhogsheads in a large chamber, and allowing steam t o escape into ever, it is believed that the increase in insoluble nitrogen in the the evacuated chamber t o furnish both heat and water to the flue-cured tobaccos is due in part to insoluble compounds formed tobacco. between sugars and amino nitrogen-containing components of The thermovacuum cycle may be composed of a number of the tobacco. The apparent increase in starch may be due t o the formation of compounds between reducing sugars and proteins steps, depending on the amount of moisture t o be added. The amount of vacuum needed in the chamber will vary with the which has been observed in foods (29). These compounds, if density of the tobacco mass being conditioned. soluble, would not appear as sugars because they would be reVery little information has been published on the effects of the moved in the clarification of the extract with lead acetate. If thermovacuum process other than that of incorporating heat they were insoluble, they probably would be broken down by the action of the enzyme in the starch analysis, and the sugar and moisture into the tobacco mam. Aksu and Enercan (f), however, studied the hygroscopic properties of several types of part of the compound would reappear as starch. Turkish tobaccos (of the 1947 and 1948 crops) before and after treatment by the thermovacuum process. They failed to find Treatment of Cigarette Tobaccos after Aging that the treatment had any effect on the hygroscopic properties The midrib of the leaf of flue-cured and air-cured tobaccos is of these tobaccos. removed from the leaf before the laminar part of the leaf is used in the. manufacture of cigarettes. The midribs are not removed from the small leaves of Oriental tobaccos. The midribs are Table XI. Composition of Flue-Cured and Burley Tobacco commonly referred t o in the industry as stems and the remaining before and after Thermovacuum Processing part of the leaf as strips. That part of the midribs removed Chemical Flue-Cured Tobacco Burley Tobacco usually represents from 16 to 20% of the total weight of the leaf. Constituent Before After Before After The midribs, in some instances, are removed from the leaves Total nitrogen, % 2.03 2.02 3.47 3.45 a-Amino nitrogen, % 0.147 0.141 0.379 0.368 before they are redried and prized, in other cases the leaves are 3.30 3.28 Nicotine, % 2.42 2.40 stemmed after the tobacco has been aged. The practice, how6.26 6.08 Petroleum ether extract, % ' 5.84 5.70 Soluble sugars, % 16.89 16.59 .... .... ever, of stemming the leaf just before it is placed in storage to Water-sol. acids, ml. 0.1 N alkali 4.52 4.16 3.75 3.61 5.52 4.86 5.01 5.59 age is on the increase. 11.30 14.21 Gisture, % 10.57 13.47 There are at least two reasons for removing the midribs from the leaf: The first is the physical character of the midribs and the other is their chemical composition. When midribs .pass Garber (16) states that as a result of increasing the moisture through the cutting machines they produce slivers and segments and heat content of flue-cured tobaccos by the thermovacuum or chunks of rib material, which interfere with the rolling and process and allowing them to cool, and repeating the treatment, cutting operations performed by the cigarette-making machines. the tobaccos undergo accelerated aging as indicated by their In consequence, the cigarettes may be imperfect in shape and the decreased content of nicotine, nitrogenous materials, and sugars. paper wrapping may be torn or perforated. The chemical composition of the midribs is different from that of the other Forty-four hogsheads of aged flue-cured strips and twenty-two hogsheads OI aged burley strips were subjected t o the thermopart of the leaf ( 6 ) , and experience has shown that the midrib vacuum process under known conditions to determine if they tissues impart a woody, peppery, and unattractive flavor to the underwent chemical changes as a result of the treatment. These smoke. The physical objection t o the stems may be overcome hogsheads averaged 950 pounds of tobacco each, and samples to be in part by compressing the midribs between rollers and then used for chemical analyses were removed from the exterior part and the interior part of the tobacco mass of each hogshead before blending the flattened tissues with the strips before passing the and after i t was subjected t o the process. The vacuum cycle used blend through the cutting machines. Only a small proportion consisted, first, of evacuating the chamber t o 5 mm. of mercury, of the stems is used in this manner. The composition of the cutting off the evacjuation system, and introducing steam into the stem and strip part of the leaves of-cigarette tobaccos of the chamber until the pressure rose to 200 mm. of mercury. The heat-cured and air-cured types are given in Table X. These second, third, and fourth steps followed in order, each consisting of evacuating the chamber to 50 mm. of mercur cutting off the data are the average .of analyses made on a large number of evacuation system, and introducing steam into tgk chamber until samples of flue-cured and Maryland tobaccos of the 1948 crop the pressure rose to 200 mm. of mercury. and on burley tobaccos of the 1949 crop. These samples repreThe evacuation of the chamber in the system used was acsent tobaccos over a wide range of cigarette grades from many complished by two steam jets and a mechanical pump. The Table X. Analyses of Strip and Stem Part of Heat- and Air-Cured Tobacco Leaves
February 1952
INDUSTRIAL AND ENGINEERING CHEMISTRY
291
steam and evacuated gases from the first steam jet are fed Table XII. Analyses of Brands of Blended Cigarettes Sold in 1949 and 1950 into a barometric condenser Chemical Conatituent where water from a cooling Total ProaNicoPetroSol. NonWatertower is sprayed directly into tine, vol. sol. leum ether sugars, Starch, N, tein Amino No. the steam, thus condensing it. acids“ acids’ pH % % % ext., % Brand Samples % N,% N, % The barometric condenser is 14.80 3 76 4.46 15.22 3.29 0 154 2 03 5.27 0.86 2.08 A 9 maintained under vacuum by 4.68 12.86 3.39 16.41 3.22 0.180 1.91 5.41 0.91 2.15 B 11 4.04 4.80 14.49 17.20 3.11 0.167 1.92 5.42 0.96 2.17 c 12 the second steam jet. The 3.41 4.60 13.69 16.60 3.32 0.173 2.10 5.33 0.90 2.17 D 14 steam from this e t and any 3.99 16.82 2.99 1.95 4.97 13.80 5.44 0.98 0.169 2.25 E 8 materials removed by it from 4.77 11.68 3.65 18.69 3.05 0.169 2.02 5.50 0.97 2.29 F 12 10.37 3.20 4.39 17.14 3.66 0.187 1.97 6.11 2.35 1.03 the barometric condenser are G 5 5.22 7.47 3.15 18.50 3.01 0.240 2.03 5.43 1.06 2.46 H 6 condensed together by a surface condenser. The surface a M1. 0.1 N alkali per gram of tobacco. condenser is cooled by water from a coolina tower. but this cooling water- does not come into actual contact with the steam as i t does in the barometric condenser. The condensate literature Cited from the surface condenser is pumped into the cooling water. (1)Aksu, Samin, and Enercan, Sadiye, Tekel Enstituteri Raporlari, The surface condenser is maintained under vacuum by a Cdd V . Sayi, 2, 202 (1949). mechanical pump throu h a vapor separator which prevents water (2)Ambler, J. A., IND. ENG.CHEM.,21,47 (1929). droplets from entering &e mechanical pump; the pump exhausts (3)Bacon, C. W., Wenger, R., and Bullock. J. F.. U. S. Deut. of from the building through a stack. Agr., Tech. Bull. 1032 (1951). Some of the materials removed from the chamber which either (4) Cooper, A. H.. Delamar, C. D., and Smith, H. B., Virginia were liquids at the cooling water temperature or soluble in water Polytechnic Institute Engineering Expt. Station Series, Bull. are removed a t the two condensers and enter the cooling water 37 (1939). circulating system, and some volatile materials are lost through (5) Crane, Hugh, Liggett and Myers Tobacco Go., New York, the exhaust of the mechanical pump. “About Cigarettes and Taxes” (1951). Samples of the exhaust from the pump and of the cooling water (6) Darkis, F. R., Baisden, L. A., Gross, P. M., and Wolf, F. A., leaving the cooling tower were analyzed and found to contain IND.ENG.CHEM.,44,297(1952). small quantities of volatile acid constituents, volatile basic con(7) Darkis, F. R.,Dixon, L. F., and Gross, P. M., Ibid., 27, 1152 stituents, and nicotine. The equivalent concentration of volatile (1935). acids was approximately three times as great as the e uivalent (8)Darkis, F.R.,Dixon, L. F., Wolf, F. A., and Gross, P. M., Zba., concentration of volatile bases in both the exhaust gaslrom the 28, 1214 (1936). pump and the cooling water from the tower. (9)Ibid., 29, 1030 (1937). (10) Darkis, F.R., Hackney, E. J., and Gross, P. M., Ibid., 39, 1631, Averaged chemical analyses of thesamples from each of the hogs(1947). heads (Table X I ) show that only minor changes of a chemical (11)Darkis, ‘F.R.,and Mattison, R., Duke University, Durham, nature occur in the tobaccos as a result of the thermovacuum N. C., Tobacco BUZZ., 1 (1947). treatment. These minor changes consist, in part, of small losses (12) Dixon, L. F., Darkis, F. R., Wolf, F. A., Hall, J. A., and Jones, E.P.,IND. ENG.CHEM..28. 180 (1936). in nicotine, amino acid constituents, and water-soluble acid (13) Frankenburg, W. G., “Advances in Enzymology,” Vol. 10,pp. constituents. As the data indicate, the moisture content of 325-441,New York, Interscience Publishers, 1950. tobacco increased b y approximately 2.90%. The temperature (14) Frankenburg, W. G., Arch. Biochem., 14, 157 (1947). of the tobacco WBB approximately 26.3O C. when it entered the U. S. Patent No. 2,353,718(July 18, 1944). (15) Garber, T. H., (16)Garner, W. W.,“Production of Tobacco,” Philadelphia., Blakisthermovacuum equipment, and it attained a maximum temperaton Co.,1946. ture which varied from 65.5 t o 71.1’ C. in the interior of the (17) Garner, W. W., U. S. Dept. of Agr., Bur. of Plant Industry, tobacco mass. BUZZ.143 (1909). The data of Table X I seem t o be in agreement with those (18) Garner, W. W.,Bacon, C. W., and Foubert, C. L., Ibid., 79 (1914). obtained on the analysis of the materials exhausted from the (19)Hobbs, M. E., and Layton, F., Duke University, Durham, N. C., thermovacuum chamber. Data on possible losses in dry weight private communication. were not obtained. (203 Jeffrey, R.N.,Kentucky Agr. Expt. Station, Bull. 407 (1940). Casing materials are applied after tobaccos have been aged and (21)Jeffrey, R. N., and Gri5th, R . B., Plant PhysioE., 22, 34 (1947). (22) Kingsbury, A. W., Mindler, A. B., and Gilwooh, M. E., C h m . stemmed-in most instances in the form of sprays after the Eng. Progress, 44, No. 7. 497 (1948); Trans. Am. Inst. Chem. various strips have been blended. I n some instances, however, Engrs., 28, 453 (1948). the casing mixtures may be applied by immersing some of the (23) Maillard, L.G.,Ann. Chem., 5 , 258 (1916). strips in baths of the casing mixture, removing the excess mixture (24)Moffett, R. B.,“Chemical Changes That Occur during the Curing and Aging of Tobacco of the Aromatic Type,” thesis, by pressure and wringing procedures, and drying to the point Duke University, Durham, N. C. (1942). where the strips can be blended with other components. When (25) Moss, E. G., and Teter, N. C., North Carolina Agr. Expt. Stathe casing is being applied, the moisture content and temperature tion, Bull. 346 (1944). of the tobacco are increased so that it is tough and flexible. (26)Nestoroff, Marco, “The Oriental Tobaccos,” Vol. 1, Dresden, Gebr. Arnold, 1928. The tobacco in this condition is taken t o the cutting machines (27) O’Bannon, L.S.,Kentucky Agr. Expt. Station, Bull. 444 (1943). where it is cut into shreds which are dried and cooled. Flavor(28)Ibid., 501 (1947). ing materials, if used, are added after cooling, and the cased, (29)Patton, A. R.,and Hill, E. G.,Science, 107, 68-9,623-4 (1948). cut, dried, and flavored tobacco shreds are ready t o be made (30)Ruckdeschel, W., Tech. Hochschule, Muncheu, dissertation (1914); 2. ges. Brauw., 37,430,437 (1914). into cigarettes. I n addition the blends may be subjected to nu(31) Smuch, A., and Semnova, V., State Institute of Tobaoco Indusmerous handling operations, such as moistening, heating, drytry, Krasnodar, U. S. S. R.,Bull. 33 (1927). ing, cooling, standing, and cleaning, which follow in a given seq(32)Stimson, F.A., “Distribution of Plastid Pigments in Flue-Cured uence, although the duration of the cycles may vary from a few Tobacco during Maturation and Curing,” thesis, N. C. State Colleze. Raleigh (1949). hours to several days. Van Sl&, D. DY, J: Bioi.-Chem., 9,185 (1911);12, 275 (1912); Starting with raw materials of variable and changing com16, 121 (1913); 23,407 (1915). position the manufacturers fabricate a product which is amazingly Ward, G.M., Dominion of Canada, Dept. of Agr., Tech. Bull. uniform over a long period of time and which varies only within 37 (1942). Woolford, R. W., “Chemical Changes Occurring during Fernarrow limits of chemical composition. The data in Table XI1 mentation of Turkish Tobaccos,” thesis, Duke University, indicate the close similarity in composition of competitive brands Durham. N. C.. 1947. of cigarettes. These analyses were made from cigarettes pur(36) Young, J. R., and’Jeffrey,R. N., Plant Physiol., 18,433 (1943). chased in retail stores in 1949 and 1950. R E O E I VAugust ~D 8, 1961.
