FLUE-CURED TOBACCO Apparent Density and Its Correlation with Chemical Composition’ F. R. DARKIS, P. M. PEDERSEN, AND P. M. GROSS Duke University, Durham, N. C.
P
REVIOUS papers of this series showed that the chemical composition (3) of flue-cured tobaccos may vary considerably and that the composition can be correlated with stalk position and climatic conditions (8, 3) as well as fertilization and soil (4). Judges and expert buyers of tobacco make use, primarily, of the physical properties in making their estimation of the quality or value of tobaccos. The density of the cured leaf is related in some manner with the so-called body (8) and texture of the leaf. It is difficult, however, to find any definite correlation between body and chemical composition (2). If any direct correlation exists between the density and chemical composition of flue-cured tobacco, it should be possible to relate, indirectly, the composition and body of the leaf. The data on the apparent density and chemical composition of tobacco presented in this paper were obtained to determine whether such a correlation exists. Only minor reference is made to the density of tobacco in the literature. Garner (6),using a displacement method, obtained data on the apparent density of air-cured (Maryland) tobacco. His results show that tobacco grown on the lower portion of the stalk is more dense than that from the top part of the stalk. Agah ( I ) , working with Turkish tobaccos, obtained data which he termed “density” by subjecting a volume of dry tobacco, ground to pass a 50-mesh sieve, to a definite pressure and calculating the density from the measurements obtained. He claimed that a direct relation exists between the density and the “constitutional factor”. The constitutional factor is the sum of the percentages of total nitrogen, protein nitrogen, protein, reducible substances, soluble carbohydrates, polyphenols, resins, and ash.
Methods and Samples The density method of Tschapek (7) as applied to tobacco (6) was used. This consists, essentially, of placing the finely ground sample of tobacco in a tared pycnometer, covering it with xylene, evacuating to 10 mm. of mercury for 15minutes, Uling the pycnometer with xylene at 30’ C., weighing, and then calculating the apparent density from the data obtained. The density data were calculated to the sand-free basis. The chemical methods were described in previous papers of this series (8,3, 4) except that for the protein nitrogen which was determined by the method outlined by Garner (6). The moisture content of each sample was between 1.0 and 2.0 per cent. The chemical analyses were made in duplicate and all results were calculated to the moisture-free and sandfree basis. Four or more determinations of the density were made on each sample. 1 Papers 1.2, 3, and 5 of this series appeared in IND. ENQ.CHBX.,27, 1152 (1935); 28, 180, 1214 (1938): 29, 1030 (1937). The fourth appeared in Bull. Torrry Rctan. Club, 64, 117 (1937).
The tobacco used consisted of the six primings or the entire production of a plot of flue-cured tobacco produced on the Oxford, N. C., tobacco experiment farm during the growing season of 1936. The samples included the lamina and midrib parts of the cured leaf of each of the six primings. The midribs, comprising about 23 per cent of the total leaf, were separated from the lamina and veinous part of the leaf by hand and ground to pass a 100-mesh sieve. The lamina, which was about 67 per cent of the total leaf, was separated from the veinous material by rubbing it through a series of sieves, from 20 to 100 mesh, with a flat pestle made from a rubber stopper. The lateral and interlateral veins remained on the sieves. The crop data are given in Table I. The chemical and density data along with the ratio of the sum of the heavier to the sum of the lighter constituents of the tobacco are given in Table 11.
Discussion Figure 1shows that the lamina as well as midrib material produced near the base of the stalk has a larger apparent density than that produced near the top of the stalk. The density of the mineral m a t e r i a l s that make up the ash 0 BOTTOM ?AVERAGE S T A L K POSITION OF P R I M I N G and the organic 0-20-40-60-80 acid compounds of these minerals F I G U E1.~ EFFECTOF STALKPOSITION ON DENSITY ranges from 2.00 to 3.00, while the density of the organic acids and carbohydrates in the tobacco ranges from about 1.50 to 1.70. These materials are found in greater proportion in that tobacco produced on the lower portion of the stalk. On the other hand, the density of nicotine and the petroleum-ether-soluble materials ranges from 0.80 to 1.20, while the density of the nitrogenous materials ranges from about 1.10 to 1.60. These materials are found in greater proportion in the tobacco produced near the top of the stalk. The density of the component parts of the tobacco tissue would be expected to be reflected in the apparent density of the tobacco. Table I1 and Figure 1 indicate that such is the 0-MID
RIBS
D-LAMINA
1549
INDUSTRIAL AND ENGINEERING CHEMISTRY
1550
case. The tobaccos of greatest density are those which contain the larger percentage of the more dense materials. Those of least density are the tobaccos that contain the larger proportion of the less dense materials. The apparent density of the midribs is greater than that of the lamina. This would be expected because of the low percentage of the less dense constituents in the midribs. There appears to be no direct correlation between the apparent density and any single constituent determined. If the
TABLEI. CROPDATA PFiming No.
1 2
3 4
5 6 Total
Wt. of Total Priming, Grams
668.0
1342.0 1738.0 2524.0 1571.0 859.0 -
-
-
8702.0
-
of Total Plant
W t . of Lamina Gra&s
Wt. of Midribs, Grams
Lamina
Midrib
% of Plant Analyzed (Rib.and Lamina)
7.68 15.42 19.97 29.01 18.05 9.87
462.0 903.0 1165.0 1650.0 1055.0 588.0
154.0 307.0 392.0 581.0 360.0 183.0
67.66 67.29 67.03 65.37 67.15 6 8.45
23.05 22.88 22.55 23.02 22.92 21.30
90.71 90.17 89.58 88.39 989.75 0.07
66.80
22.71
89.52
_
I
_
100.00
-
_
_
5813.0
%
Of Total
Priming
_
1077.0
Vol. 33, No. 12
acids) to the sum of the less dense constituents (protein, soluble nitrogen, nicotine, and petroleum-ether-soluble materials) is used. The ratio nicotine
ash + total sugars + total acids + protein + sol. nitrogen + petroleum ether extract
is in direct relation to the apparent density, if the lamina and midrib materials are considered separately. This is shown graphically in Figure 2. Within the precision of the determinations, the apparent density is a linear function of this ratio. The fact that these two types of tobacco tissue give independent straight lines with differing slopes in Av . Position dicates the operation of some additional factor. on Stalk, This may perhaps be related t o a different type % from Base of cell structure and organization in these two Tipt o tissue materials. 3.84 15.39 It was pointed out in a previous paper (1) 33.09 that "body is essentially an empirical judg57.58 81.11 ment of substance content and is not related 95.07 directly to thickness, weight per unit area, or
TABLE 11. APPARENT DENSITY A N D CHEMICAL DATA Priming No. Apparent density More dense Constituents Total sugar, % Total acid' 501. ash, % Sum
I.,ess dense constituents Protein, Yo 501. N, Yo Nicotine % Petroleuk ether ext., % 5um Ratio, more dense t o lesa dense constituents 0
kg
I/ I
2
G
G
Lamina
Midrib
1.533
1.597
1.484
5.19 21.67 16.99 43.85
7.33 23.19 20.23 50.75
2.63 1.11 0.49
3
4
~~~
6
'Lamina
Midrib
Lamina
Midrib
Lamina
Midrib
1.587
1.461
1.580
1.455
1.574
1.425
1.567
1.434
1.563
12.70 17.33 12.94 42.97
12.96 19.09 17.52 49.57
17.56 12.60 9.72 39.88
12.59 17.28 14.96
18.44 11.10 8.64
13.97 15.23 14.25
7.53 13.11 9.85
8.01 17.75 16.41
4.19 15.18 13.32
5.86 18.02 16.54
5.81 1.35 1.94 9.34
2.81 0.98 0.63 0.94
~
5.69 1.14 2.03 8.74
.14.83
38.18
45.45
30.49
6.38 1.23 2.42 8.12
lS.15
3.13 0.70 0.51 0.98
8.25 1.74 3.68 8.27 21.94
2.11
18.40
4.99
18.44
6.28
17.66
2.38
10.16
2.38
9.42
2.27
8.65
0.76
.~
Midrib
2.94 0.84 0.51 0.89 6.18
e
5
Lamina
- - - - 6.06 1.36 1.86
T
8.17
1.39
'41.17 3.31 0.94 0.50 1.14
6.89 6.99
32.69 7.75 2.13 4.02 9.36
23.26 1.41
40.42 3.44 1.14 0.54 1.23
6.35 6.37
Cc. of 0.1 A' alkali per gram of tobacco.
L
i.
1
tion between the s u m of t h e heavier constituents (ash, acids, and sugar) and the apparent density. For the midribs considered alone, the
density as such". I n general, it may be said that those t o baccos considered to possess good body are relatively high ir nitrogenous materials and petroleum-ether-soluble materials high in sugars, and relatively low in acids and ash. Those considered as heavy-bodied are high in nitrogenous materials, relatively high in acids, and low in sugar content. Those considered to be light-bodied are usually low in nit,rogenous materials, relatively low in sugars, and high in acids and ash content. The data presented in this paper, while apparently not providing a means of more directly correlating chemical composition and body, do indicate that the tobaccos lacking body are those possessing the larger apparent density.
Literature Cited Agah, Turkdogan, Inhisalar Tutun Institusn Raparlari, 2, No. 2, 185-89 (1939). Darkis, F. R., Dixon, L. F., and Gross, P.M., IND.ENG.CREM., 27, 1152 (1935). Darkis, F. R., Dixon, L. F., Wolf, F. A., and Gross, P. N., Ibid., 28. 1214 (19361. Ibid.,'29, 1030 (1937). Darkis, F.R.,Pedersen, P. M., and Gross, P. M., Ibid., t o be published. Garner, W. W., Bacon, C. W., Bowling, J. D., and Brown, D. E., U. S. Dept. Agr., Tech. Bull. 414,30 (1934). T s c h a p e k , N. W.,Kolloid-Z., 63,34-6 (1933).
