\-oL.2 7 . NO. 10
INDUSTRIAL AND ENGIXEERING CHEMISTRI-
1152
Literature Cited
G r a v e l l , [hid., 2,005,780 ( J u n e 25, 1 9 3 5 ) . (4) Hedges, " P r o t e c t i v e Films on M e t a l s , " London, C h a p m a n and H a l l , 1932. ( 5 ) Xelson, ISD. ESG. C H E ~ I 27, . , 35 (1935~. ( 6 ) Nelson a n d K i t t e l h e r g e r , I b i d . , 25, 27 ( 1 9 3 3 ) .
Ihid., 1,973.Gl3 ( S e p t . 11, 1934) :
(1) Bulkley a n d S n y d e r , J . Ana. C h e m . Soe., 55, 194 (1933). (2) C o u r t n e y a n d Wakefield, J. IXD.Exc. C'HEZI., 6,470 (19341. (3) G r a v e l l , J. H., U. S. P a t e n t 1,231,046 (April 3 , 1 9 1 7 ) ; T r i m s , JT. W.,B r i t i s h P a t e n t 362,956 (August 8, 1930); P a r k e r R u s t proof C o m p a n y , Ibid., 346,401 ( J a n . 10, 1 9 2 9 ) ; G r e e n a n d Eokelman, C a n a d i a n P a t e n t 314,036 ( M a r c h 4, 19311; P y r e n e C o m p a n y , Ltd., B r i t i s h P a t e n t 394.211 ( J a n . 21, 1 9 3 2 ) ; T a u n e r , U. S. P a t e n t 1.911,537 ( M a y 30, 1 9 3 3 ) ; C o r h i n ,
R E C E I V EM D a y 13, 1935. Presented before the Dirision of Paint and Varnish Chemistry a t the 89th Meeting o f the .irnerican Chemical Society. New lork T I.ipril 1 2 t o 2 6 , 1933.
T
HE tobacco industry has a rich background of empirical knowledge and information which awaits correlation with more exact scientific criteria such as bhe chemical composition, physical properties, and physiological behavior of tobacco as a plant. The ektablishment of such critdria is essential to the development of a worthwhile program looking to the improvement of the plant through cultural practices, selection, and fertilization. This paper presents in condensed form the results of a detailed survey, extending over five years, of fluecured tobaccos from representative tobacco markets in the entire flue-cured tobacco region from southern Virginia to Georgia. I n quantity and in rnoney value flue-cured tobacco is our most important tobacco crop. As material for this survey samples of a medium grade of tobacco used in cigarette manufacture were chosen. Their prior history is briefly as follows: After being harvested green by the farmer, the leaves are subjected to the thermal process known as flue-curing ( 3 ,6 ) b y the farmer and are then Rold on
TYPE-AREAS OF THE FLUE-CURED
Flue-Cured Tobacco Factors Determining Type and Seasonal Differences
,. F. R. DARKIS, L. F. D I X O S , AND
P. RI. GROSS
Duke University. D u r h a m , N. C.
0
STATE BOUNDARIES TYPE-AREA L I N E S PHYSIOGRAPHIC DIVS.------
-.
-
THERMAL LINES RAINFALL L I N E S
.**...60'F -45
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the market by him. The purchaser subjects them to further heat treatment and drying. This latter operation is known as redrying. Both the flue-curing and redrying operations are reasonably well standardized in practice. After being subjected to these processes, the tobacco is in the condition in which it is stored for aging. S a m p l e s taken a t this stage were utilized for this survey. Although the coniposition of the tobacco in this state differs considerably from that of the uncured green leaf, it represents the stabilized form or condition of the tobacco which most closely approaches that in which it is empirically judged as an agricultural commodity. T h e c o m p o s i t i o n a t t h i s stage can be related to the growing conditions, the soil, and the seasonal and climatic factors which influence e a c h t o b a c c o type.
OCTOBER, 193.5
INDUSTRIAL. -4ND E S G I X E E R I J G CHElIISTR1-
1153
REUUCISG AND TOTAL SUGARS.Reducing sugars xere determined before and after hydrolysis by the hlunson and Walker method ( 6 ) , and the results expressed in terms of glucose. The The redried tobacco from pressed hogsheads was sampled a extract was clarified with neutral lead acetate. fen hours after redrying. The hogsheads selected for sampling were distributed over the entire marketing season of each of the TOTAL SONVOLATILE ACIDITT. Five grams of tobacco and six types of tobacco studied. Each hogshead was composed 6 to 7 cc. of 6 M hydrochloric acid were mixed into a homogeneous mass, and finely divided neutral pumice stone was later worked of a mixture of similar grades from several markets and thus into this mass until a semi-dry mixture n-as obtained. Thib represented fairly well the tobaccos of that grade being marketed mass was extracted with alcohol-free ether for 40 hours or more at that time from a given type area. in a Soxhlet extractor. The ether was removed by the addition Samples were obtained by boring into the end of the pressed of boiling water, and the acid-containing solution was boiled and coopered hogshead, with a 2-inch (5-cm.) ship auger, to a for 5 minutes to remove volatile acids. The solution was made depth of 20 to 24 inches (50.8 t o 61 cm.) at two or more locations in the hogshead. In this manner approximately 2 pounds (0.9 to a volume of 250 cc. at room temperature, and 10-cc. aliquot5 to rvhich 100 cc. of water had been added Lvere titrated for kg.) of tobacco were obtained from 500 pounds (226.8 kg.) of acidity with 0.1 AV alkali using leaf tobacco. Analysis of conp h e no 1p h t h a le in as indicator. secutive samples taken in this Chlorine \vas determined on other manner showed that the sampling The chemical analyses of some of the 10-cc. a l i q u o t s by the Volhard method was representative and method, and its acid equivalent reproducible. These borings were groups of organic constituents of flue-cured was s u b t r a c t e d from the alkali ground in a Wiley m i l l t o p a s s cigarette tobacco are presented. The analyt i t r a t , i o n . The results are exthrough a 1-mm. sieve and then pressed in the number of ec. of sealed in a mason jar. Except in ses are for a median cigarette grade of 0.1 LV alkali required to neutralcases where analyses were made each of the six flue-cured types taken from ize the acidity in 1 gram of toimmediately, the samples were bacco. stored a t 30" to 36" F. (-1.1' to five successive crops of varied seasonal This m e t h o d a s s u m e s t h a t +2.2" C.) until analyzed. rainfall. the chlorine titrated is present as h y d r o c h l o r i c acid and not as These analyses show significant differmineral salts. The chlorine conMethods of Analysis ences in chemical composition between tent of most flue-cured tobaccos is r e l a t i v e l y low, and the soluMOISTURE. Two-gram samples the six types and indicate the basis for the bility of chlorides in alcohol-free were dried over c o n c e n t r a t e d present commercial practice of dividing ether is slight. Thus the error (above 90 per cent) sulfuric acid resulting from this assumption ia at 30" C. for 7 days. flue-cured tobaccos into six types as consmall. TOTAL NITROGEN ASD WATERtrasted with the four types recognized by SOLUBLE NITROGEN.The official Gunning method ( 1 ) of the A. 0. the federal grading system. All d e t e r m i n a t i o n - on the A. C. as applied to fertilizers, but Relationships between the chemical samples were made in duplicate. w i t h the a d d i t i o n of 0.6 gram The result, given in Table I are analyses and the type characteristics are of metallic m e r c u r y , n-as emthe average of t h e analy3iC plo ye d . pointed out, and their correlation with PETROLEUM ETHER EXTRACT. for *ix separate >ar~iple-. A11 empirical evaluation of tobacco characterF i v e - g r a m s a m p l e s of t h e result> are expre-ed on a iiioibground material were extracted istics by judges of tobacco is indicated. tire-free baqis. for 23 hours w i t h p e t r o l e u m The influence of soils, temperature, and ether (boiling point, 30" to 60" C.) on a B a i l e y - W a l k e r extraction rainfall in determining type differences is Discussion of Results apparatus (9). The residue was shown, as well as the dominant influence dried to constant weight at 95" C. The United States D e p a r t in an electric oven. of seasonal rainfall in altering chemical ment of Agriculture, in its statisNICOTINE. The Keller method composition and in producing distinctive as modified by Garner ( 2 , 4 ) was tical work, divides flue-cured used. crop characteristics. tobaccos i n t o four types. T o b a c c o s from the Old Belt The amino nitrogen, soluble Flue-Cured a n d M i d d l e Belt nitrogen, reducing sugar, and total sugar were determined on Flue-Cured regions, comprising a portion of the c7entral and a n extract made by extracting 25 grams of the ground tonorth central counties of Xorth Carolina and the south central bacco with 375 cc. of water, with the addition of 1 cc. of counties of Virginia, make up U. d. Type 11. Eastern S o r t h chloroform, in a mason jar, a t room temperature for 14 to 16 Carolina Belt tobaccos from the northern two-thirds of the hours, with occasional shaking for the first hour. The p H Coastal Plain of S o r t h Carolina are U. S. Type 12. The was determined on an extract of the same proportions of South Carolina and Border Markets tobaccos, from the lower tobacco and water but with the omission of the chloroform. third of the North Carolina Coastal Plain and adjacent and The extracts were either filtered through a linen cloth or a equal territory in South Carolina, make u p U. S. Type 13. plug of glass wool. U. S. Type 14, consisting of Georgia and Florida Flue-Cured, The possibility of enaynatic action during this extraction is is produced in southern Georgia and in a small adjacent area considered negligible. According to Treyer (7) such action in northern Florida. is inhibited b y the presence of chloroform. Unpublished For purposes of blending, flue-cured cigarette tobaccos are studies in this laboratory of similar samples of flue-cured usually divided into six types on the basis of the area in which tobacco have shown their enzyme content to be \very small. they are produced. These areas are shown on the map and This is to be expected in view of the drastic thermal treatment differ from the federal classification in that TT. S. Type 11 is flue-cured tobaccos receive during the curing process (90' t o subdivided into three sections or types-the Durham, W n s 95" C. for 12 hours or more). This conclusion is further conton, and D a n d l e . Eastern North Carolina is U. S. Type 12, firmed b y the fact that in extractions under temperatures South Carolina is U. S. Type 13, and Georgia is U. S.Type 14. ranging from 5" to 30" C. no differences in nitrogen or sugar These divisions are of real significance in that they reprecontent were found. sent differing temperatures, rainfall, soil types, and growing seasons. The mean temperatures and rainfall are indicated AMINO NITROGEN. The Van Slyke method was used (8). on the map. The soil types in the Coastal Plain are mainly HYDROGEN-ION CONCENTRATION. The hydrogen electrode Malboro, Sorfolk, Craven, Ruston, Bradley, Dunbar, and (Hildebrand) was used, and the results were expressed in terms of Tifton sandy loanis. The principal soil types in the PiedPH.
Alethods of Sampling
INDUSTRIAL A S D ENGINEERIXG CHEMISTRY
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VOL. 27. S O . 10
Table I shows that the Piedmont tobaccos are higher in total and soluble nitrogen than the Coastal Plains tobacco although the insoluble (protein) nitrogen is not appreciably higher. The total nonvolatile acids, nicotine, and petroleum ether extract are higher in the Piedmont tobaccos. The Piedmont tobaccos are considerably higher (25 per cent) in nicotine content than those produced on the Coastal Plains. The petroleum ether extract, which appears t o be affected more by rainfall than by geographical location, is considerably higher (12 per cent) in the Piedmont tobaccos. Shortage of rainfall increases the amount of this extract, and excess rainfall reduces it regardless of the section concerned. Although differences in hydrogen-ion concentration exist between the various types, when a division is made into the two major types mentioned no difference is found. The sugar content is greater in the Coastal Plain tobaccos. This is especially true of the Georgia and to some extent of the South Carolina type. The lowest carbohydrate content is found in the Winston and Danville types which are produced in the northwestern portion of the flue-cured area. As the commercial utilization of the various tobacco types is based on their geographical origin, it is worth while to relate their trade characteristics and chemical composition to the conditions under which they are produced. GEORGIA TYPE. This is a thin, ydllow, hygroscopic tobacco of good smoking quality. It is characterized by its silky texture, its hygroscopicity, and its decided tendency to redden or darken during aging. This latter characteristic is detrimental from the viewpoint of the export trade. This tobacco is produced largely on Tifton and Norfolk sandy loam soils in a subtropical climate of mean annual temperature of 67+ O F. and a mean annual rainfall of 43 to 50 inches. The growing conditions and characteristics of this type of
niont area are Durham, Granville, Appling, Cecil, Helena, and Surry sandy loanis. The planting season in Georgia extends from March 20 to April 20; in South Carolina from April 1 to April 2 5 ; in eastern Xorth Carolina from ilpril 15 t o May 5 ; in Durham from May 1 t o May 20; and in the IT'inston and Danville areas from May 20 to June 10. The harvesting period in Georgia is from June 1 to July 20; in South Carolina from July 1 to August 15; in eastern North Carolina from July 1.5 to August 2 5 ; in Durham from July 25 t o September 15; in the Winston region from August 20 to September 25; and in the Danrille area from August 25 to October 1. The greatest differentiation in character and composition of the tobacco mag' be obtained by dividing the entire fluecured tobacco section into the two major geographical divisions of Coastal Plain and Piedmont. The Coastal Plain tobaccos comprise the Georgia (U. S. Type 14), South Carolina (U. S. Type 13), and Eastern Xorth Carolina (U. S. Type 12). The Piedmont tobaccos are composed of the Durham (U. S. Type ll), Winston (U. S. Type ll), and Danville (U. S. Type 11). The Coastal Plain tobaccos are, generally speaking, lightbodied1 thin tobaccos of very yellow color, whereas the Piedmont tobaccos are thicker, gummier, heavier bodied, of darker color, more aromatic, and of fuller2 smoking quality. I "Body" is a technical trade term of great significance t o judges of tobacco, which cannot readily be given exact scientific definition. I t is essentially a n empirical judgment of "substance content" and is not related t o thickness, weight per unit area, or density, as such. I t s opposites are characterized as "washed out" or "chaffy." I t denotes the 2 "Fullness" is a term descriptive of smoking reaction. extent t o which a certain tobacco will satiate the desire t o smoke. I t is not necessarily connected with "strength," a term which a t t e m p t s t o describe the degree t o which t h e smoke of certain tobacco is irritating.
CIGARETTE TOBACCO FOR TABLEI. AVERAGEAXALYSISOF SIX TYPESOF FLUE-CURED Portion of Total i X Total N Soluble
WaterSol.
-4mino
Total Sugar
Total Acidity
THE
1928-32 CROPS Petroleum Ether Extract
N
Nicotine
Reducing Sugar
52
%
%
%
%
%
%
cc
1928 1929 1930 1931
64.5 63.0 64.2 70.4 65.9
1.72 1.65 1.51 1.69 1.64
1.11 1.04 0.97 1.19 1.08
0,142 0.169 0.170 0.227 0.177
Coastal Plain 2.27 2.33 2.28 2.91 2.45
20.73 22.74 24.35 20.91 22.18
21.61 23.59 25.12 21.45 22.94
12.36 12.99 12.49 13.11 12.74
5.17 5.30 5.51 5.27 5.31
5.17 4.98 4.85 6.83 5.46
Above normal Excessive Below normal Deficient
1928 1929 19x0 1931 1932
1.70 1.76 1.78 1.67 1.90 1.76
1.11 1.10 1.16 1.13 1.13 1.13
0.179 0.191 0,195 0,227 0.219 0.202
2.03 2.04 2.48 2.52 2.73 2.36
19.25 21.40 20.31 19.13 18.62 19 74
20.38 22.16 21.22 19.56 19.26 20.52
11.64 11.87 12.04 13.19 11.19 11.99
5.21 5.32 5.11 5.26 5.11 5.20
5.63 4.97 5.73 6.71
Above normal Excessive Below normal Below normal Below normal
Av. for 5 crops
65.3 62.5 65.2 67.7 59.5 64.2
LXO 1.91 2.12 1.70 2.08 1.92
1.14 1.12 1.35 1.04 1.36 1.20
0,201 0.226 0,226 0,190 0.189 0,206
2.09 2.20 3.01 2.18 3.35 2.57
18.10 17.75 17.51 20.54 17.63 18.31
18.85 18.38 18.27 21.08 18.30 18.98
12.95 12.94 12.88 12.28 14.43 13.09
5.15 5.27 5.18 5.14 5.01 5.15
5.82 5.18 6.68 6.00
Av. for 5 crops
63 3 58.6 63.7 61.2 65.4 62.5
5.92
64.2
1.78
1.14
0.196
2.46
19.93
20.66
12.60
5.22
5.70
14.67 19.06 17.74 19.75 16.85 17.61
15.52 19.84 18.39 20.47 17.60 18.36
11.97 13.13 14.02 12. 94 14.63 13.34
5,20 5.29 5.24 5.20 5.09 5.20
6.92 5.50 7.28 6.63
Type
Georgia
Crop
AT. for 4 crops South Carolina
Av. for Coastal Plain area
N
.
PH
..
5.76
..
A v . for 5 crops
65.9 60.4 68.8 61.8 67.5 64.9
2.08 1.87 1.99 1.78 2.00 1.94
1.37 1.13 1.37 1.10 1.35 1 26
0,223 0,194 0.225 0,186 0.197 0.205
Piedmont 3.07 2.46 3.41 2.51 3.41 2.97
2.25 2.08 "17 1.88 2.00 2.08
1.43 1.39 1.46 1.23 1.38 1.38
0,263 0,242 0,239 0,244 0,233 0,244
2.90 2.54 :.79 -.38 2.99 2.92
14.12 17.03 16.39 17.95 16.18 16.33
14.96 17.70 17.02 18.54 16.86 17.02
13.90 14.29 15.61 14.45 16.87 14.86
5.28 5.30 5,29 5.33 5.21 5.28
6.38 5.32 6.85 6.46
Av. for 5 crops
63.6 66.8 67.3 65.4 69.0 66.3
2.01 1.76 2.07 1.81 1.93 1.92
1.34 1.14 1.40 1.14 1.32 1.27
0,198 0,188 0,208 0,212 0,183 0.198
3.41 3.13 3.90 2.84 3.54 3.36
13.87 17.26 15.98 16.24 17.04 16.08
14.70 17.94 16.61 18.80 17.77 17.16
14.01 13.94 15.00 14.19 15.38 14.50
5.36 5.36 5.13 5.31 5.11 5.25
6.61 5.54 7.48 6.40
Av. for 5 crops
66.7 64.8 67.6 63.0 68.4 66.1 65.7
1.98
1.30
0,215
3.08
16.68
17.51
14.29
5.25
6.46
Av. for Piedmont area
Rainfall
%
..
Above normal Excessive Deficient .4bove normal Deficient
Late rains Excessive Deficient Above normal Deficient
6.58
..
Late rains Excessive De t i c i e n t Above normal Deficient
6.25
..
6.51
Late rains Excessive Deficient Above normal Deficient
OCTOBER, 1933
ISDUSTRIAL .\SD ESGISEEl3Ih G CHEMISTRY
1155
TI-PE OF B ~ R USED Z IN FLUE-CURIZG .it left a truckload of green tobacco t h a t has been "strung:' is being unloaded and hung in the curing barn. in the lean-to. At right, a pile of wood supplies the furnace.
flue-cured tobacco are related to the chemical composition as shown by the type average5 (Table I). The thinness, yellow color, and hygroscopicity are reflected in the relatively low nitrogen and very high carbohydrate content. In thi3, as in other case3 to be noted later, reddening or darkening during aging accompanies a high percentage of total nitrogen that is soluble and seems to indicate a definite correlation between them. The nicotine content is below a median value but greater than would be expected in tobaccos of 23 per cent carbohydrate content. SOUTHCAROLINA TYPE. This is a thin, yellow tobacco, of rather silky texture, of slightly more body than the Georgia, and with some tendency to darken during the aging process. This tobacco is generally produced on Sorfolk, Malboro, Portsmouth, Ruston, and Dunbar sandy loam soils, in a warm temperate and subtropical climate with a mean annual temperature of 62" to 65" F., and a mean rainfall of 45 to 50 inches. Two small areas with different rainfall are noted on the map. I n the vicinity of Chadbourn, N. C., is a small, lowrainfall area (40 to 50 inches), Tvhereas in the vicinity of Mullins, S. C., there is a high-rainfall region (50 to 60 inches). The tobacco from these m a l l areas correlates with the rainfall conditions both as to character and composition. Table I shows that the South Carolina type has an increased total nitrogen and decreased total sugar as compared with Georgia, but its composition is definitely that of a lightbodied, yellow tobacco. As previously indicated, in view of the percent'age of total nitrogen that is soluble, we would not expect this type to darken as much during aging as the Georgia type, but rather more than the eastern S o r t h Carolina type. Empirical observations on color changes during the aging of these types confirm this theory. I n this connection it should be stated that good response to aging and proper aroma development are associated with darkening of color. I n other words, the Georgia type will develop aroma and age more satisfactorily from the standpoint of domestic consumption than the South Carolina or eastern S o r t h Carolina types. On the other hand, from the viewpoint of color preservation, which is of importance in export tobaccos, the eastern S o r t h Carolina is best, the South Carolina second best, and t'he Georgia least desirable. The nicotine cont,ent
The furnace smokestack is
of the South Carolina type is the lowest for any of the fluecured tobacco.. Here, as in other instances, low nicotine content and low petroleum ether extract appear to be correlated with production in a high-rainfall area. EASTERN SORTH CAROLINA TYPE. This is a thin, bright yellow tobacco which retains its color excellently. This type reacts to aging slowly and is not very aromatic. It is of equal or slightly heavier body t'han the South Carolina and Georgia types, and is not so hygroscopic. This tobacco is produced largely on Malboro, Korfolk, and Craven sandy loams in a region of mean annual temperature of 60" to 63 O F. and mean annual rainfall of 45 to 53 inches. d small portion of the area has a rainfall of 50 to 60 inches as indicated on the map. Tobaccos from this particular area are of very poor quality, are washed out or soggy in character, and do not represent the type area. The analysis of this tobacco (Table I) shows an increasing nitrogen, nicotine, total acid, and petroleum ether extract content, and a lowered t>otalsugar content as compared with the Georgia and South Carolina types. It is the most acid of all the flue-cured types as shown by pH measurements of water extracts. The analysis is typical of thin, light-bodied, yellow tobaccos, and is distinctive by reason of the low percentage of total nitrogen that is soluble. This is in line with the slow response to aging and the color retention of this type. This characteristic is responsible for the demand for this type by the export trade. DURHAM TYPE. This is produced in the eastern Piedmont region of S o r t h Carolina, adjacent to the eastern S o r t h Carolina area. Generally it is thicker, more gummy, heavier bodied, slightly more orange in color, and of fuller smoking quality than the Coastal Plain tobaccos. It is more responsive to aging and becomes darker in color than the eastern North Carolina or South Carolina types. It is produced largely on Durham, Granville, rippling, Cecil, White Store, Slamance, and Helena loams. This wide variety of soils coupled with a low (42 to 45 inch) and median (45 to 50 inch) rainfall, and the fact that there is a fairly large thermal gradient through the area, tends to make Durham the most irregular of all the flue-cured types. The analysis of this type of tobacco (Table I) shows i t to
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INDUSTRIAL AKD ENGINEERIUG CHEMISTRY
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age well and with tlie tendency to darken color and to develop aroma.
111
Rainfall I t has lieeii shown that the character and clieniical corripo>ition of tobacco varies wvitli tlie normal rainfall preralent in the different area.? where each type i.; grown. It' has also been noted that smaller areas, witliin the type area., n-here the rainfall varie. considerably from that of the area as a n-hole, produce tohacco~of decidedly different c 11 a r a c t e r a n d q u a l i t y . Furthermore, difference in seasonal r a i n f a 1 1 coninion to all type. IY 11 affect all type.
