Unconventional Sources of Dietary Fiber - American Chemical Society

18 Chemical and Physical Properties of Tobacco Fiber

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on April 13, 2016 | http://pubs.acs.org Publication Date: April 11, 1983 | doi: 10.1021/bk-1983-0214.ch018

VIDA D. SHEEN and S. J. SHEEN University of Kentucky, Department of Plant Pathology, Lexington, KY 40646

Fiber complexes of ten tobacco cultivars as by-products of the leaf protein extraction process contain levels of neutral and acid detergent fiber comparable to that of alfalfa fiber and in excess of that in wheat bran. Compositional analyses revealed lesser concentrations of cellulose, lignin, and lipid but a greater amount of hemicellulose in tobacco than in alfalfa. In reference to wheat bran, tobacco fiber has comparable amounts of Na, P, S, Mn, and Cu but at least 20-fold more Ca and severalfold more Fe. Among tobacco cultivars, dark green tobaccos accumulate more starch and protein than burley and Turkish types. Quantitative variation of cellulosic components and minerals is also evident among tobaccos. Average bulk fiber volume of tobacco cultivars is 14.2 mL/g as compared to 9.5 and 4.5 mL/g for alfalfa fiber and wheat bran, respectively. The water retention capacity of tobacco fiber (9 g water/g) is nearly double that of alfalfa fiber and eight times greater than wheat bran. Cation exchange capacity ranks the highest for tobacco, followed by alfalfa and then wheat bran. Sodium taurocholate binding capacity is comparable among the three fiber sources although the fiber complex of flue-cured tobaccos absorbs more than others. The above properties of tobacco fiber complex suggest its potential as a source of dietary fiber. Epidemiological evidence i n causative r e l a t i o n s h i p s between f i b e r - d e p l e t e d d i e t s and c e r t a i n c h a r a c t e r i s t i c a l l y Western diseases has stimulated research i n t e r e s t i n the p h y s i o l o g i c a l and physico-chemical p r o p e r t i e s of various d i e t a r y f i b e r s i n the past decade ( 1). D i e t a r y f i b e r s are composed of c e l l u l o s e , l i g n i n , and n o n c e l l u l o s i c polysaccharides, a l l of which are the

0097-6156/83/0214-0251$06.00/0 © 1983 American Chemical Society

Furda; Unconventional Sources of Dietary Fiber ACS Symposium Series; American Chemical Society: Washington, DC, 1983.


252

UNCONVENTIONAL SOURCES OF DIETARY FIBER

components of plant c e l l w a l l . Pure c e l l u l o s e exerts l i t t l e p h y s i o l o g i c a l f u n c t i o n , whereas l i g n i n and n o n c e l l u l o s i c polysaccharides are capable of binding f a t t y a c i d s , b i l e a c i d s , and carcinogens (2, 3). Substances such as s t a r c h , p r o t e i n , l i p i d , p h y t i c a c i d , and minerals are u s u a l l y associated with d i e t a r y f i b e r i n forming a d i e t a r y f i b e r complex that a l t e r s physico-chemical p r o p e r t i e s of the f i b e r . Among the common foods of p l a n t o r i g i n , breakfast c e r e a l s and wholemeal breads containing wheat bran are high d i e t a r y - f i b e r foods f o r both h e a l t h conscious people and f o r the treatment and c o n t r o l of diabetes (4). Enrichment of foods with f i b e r from c e r e a l h u l l , c i t r u s pulp, guar gum and woody t i s s u e s i s p r e s e n t l y i n the experimental stage. Although f i b e r s i n the n a t u r a l foods of human d i e t are primarly derived from l e a f y vegetables, the p u r i f i e d d i e t a r y f i b e r s of l e a f t i s s u e o r i g i n are not commer c i a l l y available. The recent achievement i n e x t r a c t i o n of l e a f p r o t e i n from young tobacco plants has advanced the p o s s i b i l i t i e s f o r u t i l i z ing tobacco plant m a t e r i a l s i n human foods (5). Young tobacco plants grown under high density produced l e a f biomass two to three times greater than s t a l k weight (6). Fibrous residue of young tobacco p l a n t s from the l e a f p r o t e i n e x t r a c t i o n process can be a p o t e n t i a l d i e t a r y f i b e r i f the r e s i d u e , a f t e r removal of p l a s t i c pigments, possesses d e s i r a b l e physicochemical p r o p e r t i e s . The present study was t h e r e f o r e under taken to evaluate the d e c o l o r i z e d tobacco f i b r o u s residues f o r chemical and p h y s i c a l p r o p e r t i e s and to compare them with wheat bran and a l f a l f a f i b r o u s residue. Because of a broad genetic v a r i a t i o n i n morphology and chemical composition of p l a n t s w i t h i n N i c o t i a n a tabacum, the present study compared a number of tobacco types. M a t e r i a l s and Methods A f i e l d experiment i n v o l v i n g ten tobacco c u l t i v a r s representing f l u e - c u r e d , dark f i r e - c u r e d , burley, Turkish and Maryland types was conducted i n Lexington, Kentucky, i n e a r l y s p r i n g 1980. About 110-120 p l a n t s per p l o t (1.5 χ 1 m) per c u l t i v a r were e s t a b l i s h e d by d i r e c t - s e e d i n g and c u l t u r e d accord ing to conventional p r a c t i c e s i n the burley growing r e g i o n . When p l a n t s reached 50 cm or t a l l e r i n the middle of June, a l l plants w i t h i n a 0.36 m area were cut about 12 cm from the ground as one sample with three samples taken per p l o t . A t o t a l of 30 samples were separately processed to obtain deproteinized and d e c o l o r i z e d f i b e r complex. D e p r o t e i n i z a t i o n of f r e s h tobacco p l a n t s was accomplished by homogenization i n a high capacity Waring blender with an equal weight of i c e - c o l d 2% sodium m e t a b i s u l f i t e s o l u t i o n . The homogenate was s t r a i n e d through three l a y e r s of cheese-cloth and one l a y e r of M i r a c l o t h and, subsequently, the green f i b r o u s 2



18.

SHEEN AND SHEEN

253

Tobacco Fiber

residue was washed with a s u f f i c i e n t volume of c o l d water to remove r e s i d u a l s o l u b l e p r o t e i n . The d e p r o t e i n i z e d green f i b r o u s residue was washed with s e v e r a l volumes of c o l d 80% isopropanol u n t i l cream c o l o r e d . In a d d i t i o n , three samples of f r e s h a l f a l f a (before the flower bud stage) which'were d e p r o t e i n i z e d and d e c o l o r i z e d by the same process and wheat bran from a commercial m i l l were included f o r comparison. A l l samples were sieved through a 9-mesh screen and oven-dried (70 C) overnight before chemical and p h y s i c a l c h a r a c t e r i z a t i o n . A l l f i b e r complexes were analyzed f o r p r o t e i n , s t a r c h , l i p i d , c e l l u l o s e , l i g n i n , and ash concentrations. Protein quantity was c a l c u l a t e d from the d i f f e r e n c e i n f r e e and t o t a l amino a c i d contents before and a f t e r 6Ν HC1 d i g e s t i o n . Ninhyd r i n r e a c t i o n of amino acids was c o l o r i m e t r i c a l l y determined at 570 nm with known q u a n t i t i e s of amino a c i d s as standards (7). Starch was quantitated at 600 nm by the modified i o d i n e s t a i n method of Gaines and Meudt (8). The weight d i f f e r e n c e before and a f t e r overnight Soxhlet e x t r a c t i o n of f i b e r complex with hexane measured l i p i d content. C e l l u l o s e and l i g n i n q u a n t i t a t i o n on an ash-free b a s i s was performed through g r a v i m e t r i c methods (9). Ash content was the r e s i d u a l weight of c e l l u l o s e and l i g n i n a f t e r c h a r r i n g i n a muffle furnace at 550 C f o r 4 hr. The d i f f e r e n c e of the above s i x components from 100% was considered as apparent h e m i c e l l u l o s e which includes h e m i c e l l u l o s e , p e c t i c substances, gums, and mucilages, i f present. The same samples were analyzed f o r n e u t r a l and a c i d detergent f i b e r (NDF and ADF) content according to Van S o e s t s methods (10). Mineral elements except phosphorus and molybdenum i n the tobacco f i b e r were analyzed by use of Varian AA-6 Atomic Absorption Spectrophotometer. Samples were wet-ashed i n n i t r i c and p e r c h l o r i c acids (9:1, v/v) u n t i l completely d i g e s t e d . A f t e r evaporation to dryness, the ashes were s o l u b l i z e d i n IN HC1 f o r analyses. Q u a n t i t a t i o n of phosphorus was a c o l o r i m e t r i c method using a Technicon Autoanalyzer and the c o l o r r e a c t i o n of F i s k e and Subbarow (11). Molybdenum was quantitated by the method of E i v a z i et a l (12) which determines, with good r e p r o d u c i b i l i t y , a quantity as low as 0.02 ppm i n plant m a t e r i a l s . P h y s i c a l p r o p e r t i e s measured i n the present study included bulk volume, water r e t e n t i o n c a p a c i t y , and c a t i o n exchange c a p a c i t y . Bulk volume measurement was the method of Montgomery and Baugardt (13). whereas water r e t e n t i o n c a p a c i t y was the amount of water r e t a i n e d by the f i b e r against a c e n t r i f u g a l f o r c e of 14,000 g f o r one hr a f t e r a 24 hr hydration p e r i o d at 20 C (14). For determination of c a t i o n exchange c a p a c i t y , the f i b e r complex was soaked i n 2 Ν HC1 f o r 24 hr followed by wash ing with deionized water. Hydrogen ions were d i s s o c i a t e d from the f i b e r complex with 2N n e u t r a l NaCl s o l u t i o n which was then t i t r a t e d against 0.05N NaOH (14). Binding of sodium taurocholate by the f i b e r was the method of Kritchevsky and Story (15). A 50 or 100 mg sample of f i b e r 1



254


was incubated i n 5 ml of HPLC-grade water c o n t a i n i n g 0.15 M NaCl and 8 mM (40 μ moles) o r 40 mM (200 μ moles) sodium taurocholate at 37 C f o r one hr with gentle shaking. For the c o n t r o l , 5 mL of 0.15 M NaCl s o l u t i o n devoid of sodium taurocholate was added to the t e s t i n g sample. Sodium taurocholate i n the same NaCl s o l u t i o n with a concentration s e r i e s of 40 mM, 20 mM, 10 mM, 5 mM and 2.5 mM was processed by the same procedure to e s t a b l i s h a c a l i b r a t i o n curve. A f t e r i n c u b a t i o n , the sample was f i l t e r e d through a 0.2 μπι microporous f i l t e r and the f i l t r a t e was ready f o r HPLC a n a l y s i s . V a r i a n Model 5000 L i q u i d Chromatograph equipped with a Vari-Chrom UV-Vis Detector was used. The HPLC c o n d i t i o n s were: Micro Pak MCH-10 column (30 cm X 4 mm I.D.); eluent, 70% MeOH and 30% 0.15 M NaCl s o l u t i o n , i s o c r a t i c ; flow r a t e , 1 mL/min; d e t e c t i o n at 210 nm. With a 10 μL i n j e c t i o n and 15 min c y c l e , sodium taurocholate can be detected w i t h i n 5 min. C o n t r o l samples d i d not show any peaks with r e t e n t i o n times s i m i l a r to that of sodium t a u r o c h o l a t e . N i c o t i n e contamination i n tobacco f i b e r was assayed by the GLC equipped with an a l k a l i n e flame i o n i z a t i o n d e t e c t o r . The e x t r a c t i o n procedure and GLC c o n d i t i o n s have been d e t a i l e d i n a recent paper ( 6 ) . The s e n s i t i v i t y o f d e t e c t i o n i s below 1 ppm. A l l data were subjected to v a r i a n c e analyses. Whenever v a r i a t i o n among f i b e r sources was s t a t i s t i c a l l y s i g n i f i c a n t , the l e a s t s i g n i f i c a n t d i f f e r e n c e (LSD) a t the 5% and 1% l e v e l of p r o b a b i l i t y was c a l c u l a t e d f o r s t a t i s t i c a l i n f e r e n c e of the results. Results Chemical composition of tobacco and a l f a l f a d e p r o t e i n i z e d and d e c o l o r i z e d f i b e r complexes and wheat bran i s given i n Table I. Dark green tobaccos i n c l u d i n g f l u e - c u r e d (NC 95, NC 2326 and Coker 139), dark f i r e - c u r e d (Ky 171 and Ky 151) and Maryland (MD 609) types had comparable amounts of p r o t e i n with a mean of 15 g/100 g dry wt. The average value of the three burleys (Ky 16M, Burley 21 and Ky 14) was 9.46 g/100 g dry wt with Burley 21 showing s i g n i f i c a n t l y l e s s than the other two. Turkish tobacco Xanthi nc resembled burley i n p r o t e i n content. Alfalfa f i b e r had a p r o t e i n concentration s i m i l a r to that of dark green tobacco, whereas wheat bran contained a s i g n i f i c a n t l y higher l e v e l among the f i b r o u s samples under comparison. For s t a r c h content, a s i g n i f i c a n t c o n t r a s t e x i s t e d between dark green tobacco and b u r l e y o r Turkish type with the exception of MD 609 resembling burley i n low s t a r c h concentration. I n c i d e n t a l l y , Maryland and b u r l e y tobaccos are a i r - c u r e d types. That s t a r c h content was low i n a l f a l f a f i b e r and reached as high as 30% weight i n wheat bran was not unexpected owing to the nature of the corresponding p l a n t p a r t s . There was l i t t l e d i f f e r e n c e i n l i p i d c o n c e n t r a t i o n among the f i b r o u s residues of tobacco and a l f a l f a with a mean of 2.82 g/100 g dry wt. More than three


Furda; Unconventional Sources of Dietary Fiber ACS Symposium Series; American Chemical Society: Washington, DC, 1983. 0.99 1.34

1.20 1.63

2.44 3.31

LSD 0.05 LSD 0.01

2.44 3.06 2.78 2.40 3.38 3.55 2.67 2.48 3.09 2.32 2.80 9.54

4.30 2.01 2.22 2.42 1.38 0.90 0.33 0.09 0.18 0.88 0.60 30.67

13.54 15.48 15.61 15.88 14.27 12.21 6.02 10.14 8.41 15.23 13.12 18.51

Lipids

Tobacco NC 95 NC 2326 Coker 139 Ky 171 Ky 151 Ky 16M Burley 21 Ky 14 Xanthi nc MC 609 Alfalfa Wheat bran

Starch

Protein

Lignin

41.51 41.50 47.25 41.85 42.15 47.89 45.15 42.07 46.98 51.06 50.71 11.56 2.28 3.10

53.46 53.36 55.91 50.42 55.36 56.06 53.84 51.84 61.04 55.74 61.84 47.05 5.26 7.15 3.62 4. 93 1.09 1.48

2.53 3.44

1.07 1.46

ADF

35. 52 33. 33 26. 08 36. 62 32. 75 35. 86 39. 71 42. 15 36. 27 25. 63 25. 05 24. 11

NDF

5. 68 4. 13 8. 25 4. 85 5. 10 5. 38 5. 77 4. 55 6. 24 7.15 9. 91 2.94

Apparent hemicellulose

31.38 33.88 32.21 28.09 33.83 32.68 32.71 30.60 35.19 34.00 44.23 10.17

g/100 g dry wt

Cellulose

7.14 8.11 12.55 10.75 9.31 9.41 12.79 9.94 10.79 14.79 4.20 5.80

Ash

Chemical Composition of Tobacco and A l f a l f a Fibrous Residues and Wheat Bran.

Fiber source

Table I.



256


times t h i s amount was found i n wheat bran. Ash content v a r i e d widely among tobacco f i b r o u s samples which had an average q u a n t i t y of 10.56 g/100 g dry wt. The ash content i n a l f a l f a f i b e r and wheat bran was about one-half or l e s s than that i n tobacco f i b e r . On the same weight b a s i s , wheat bran had only 1/3 to 1/4 the c e l l u l o s e q u a n t i t y present i n tobacco and a l f a l f a f i b e r s . A l f a l f a f i b e r was a l s o r i c h i n l i g n i n with a q u a n t i t y three times greater than that i n wheat bran. L i g n i n q u a n t i t y i n tobacco f i b e r was in-between those of a l f a l f a f i b e r and wheat bran; however, s i g n i f i c a n t d i f f e r e n c e s e x i s t e d w i t h i n and between tobacco types. Such a range of v a r i a t i o n was a l s o evident f o r the q u a n t i t y of apparent h e m i c e l l u l o s e i n tobacco samples. Apparent h e m i c e l l u l o s e content i n a l f a l f a f i b e r and wheat bran was i n d i f f e r e n t to the tobacco c u l t i v a r s being on the low concent r a t i o n end of the v a r i a t i o n . Q u a n t i t a t i v e v a r i a t i o n of NDF and ADF was present among tobacco c u l t i v a r s but they lacked the same p a t t e r n of v a r i a t i o n . The tobacco c u l t i v a r means f o r NDF and ADF q u a n t i t y were 54.70 and 44.74 g/100 g dry wt, r e s p e c t i v e l y . These values were s i g n i f i c a n t l y higher than those of wheat bran. A l f a l f a f i b e r had the highest amounts of both detergent f i b e r s although the amounts were not s t a t i s t i c a l l y d i f f e r e n t from those of the tobacco c u l t i v a r s ranked high i n detergent f i b e r content. I t has been shown that f i b e r - r i c h d i e t s may impair the u t i l i z a t i o n of a number of e s s e n t i a l minerals i n c l u d i n g calcium, i r o n , z i n c , copper, and phosphorus (16). This can be c o r r e c t e d by d i e t a r y i n t a k e of minerals from a v a r i e t y of foods, on the one hand, and the endogenous source of e s s e n t i a l minerals i n the d i e t a r y f i b e r , on the other. Eleven mineral elements were t h e r e f o r e q u a n t i t a t e d i n tobacco and a l f a l f a f i b e r s and wheat bran (Table I I ) . In r e f e r e n c e to wheat bran, tobacco f i b e r contains comparable or s l i g h t l y higher l e v e l s of sodium, phosphorus, s u l f u r , manganese and copper but at l e a s t 20-fold more calcium and s e v e r a l - f o l d more i r o n . Iron c o n c e n t r a t i o n v a r i e d n e a r l y f i v e - f o l d among tobaccos. Wheat bran was r i c h i n potassium, magnesium, and molybdenum. A l f a l f a f i b e r showed a c l o s e resemblance to tobacco i n mineral content except f o r calcium, magnesium, and copper, which were s i g n i f i c a n t l y l e s s . Rasper (17) studied p h y s i c a l c h a r a c t e r i s t i c s of d i e t a r y c e r e a l f i b e r i n c l u d i n g those from wheat bran and reported that bran f i b e r had bulk volume around 3 to 5 mL/g depending upon p r e p a r a t i o n method. The wheat bran sample i n the present experiment gave the bulk volume of 4.53 mL/g which i s i n good agreement with the values c i t e d i n l i t e r a t u r e . The bulk volume of a l f a l f a and tobacco f i b e r s doubled and t r i p l e d the wheat bran value (Table I I I ) . Among tobaccos, Xanthi nc gave the l a r g e s t bulk volume and NC 2326 the l e a s t . The v a r i a t i o n seemed to be s i g n i f i c a n t f o r f l u e - c u r e d tobaccos but not f o r b u r l e y s . The average water r e t e n t i o n c a p a c i t y of tobacco f i b e r was 9 g water/g with a range of 7.40 to 10.86. Therefore, tobacco f i b e r held



LSD 0.05 LSD 0.01

NS NS

0.49 0.39 0.44 0.45 0.42 0.53 0.64 0.48 0.51 0.52 0.35 0.35

Na

0.29 0.39

0.28 0.24 0.90 0.49 0.38 0.69 0.71 0.51 0.55 0.96 0.11 1.46

Κ %

0.45 0.61

1.98 2.03 2.53 2.71 2.68 2.68 2.95 3.08 2.92 3.12 1.22 0.11

Ca

0.22 0.30 0.43 0.30 0.41 0.26 0.27 0.34 0.31 0.36 0.14 0.20 0.09 0.13

0.06 0.08

0.06 0.08

S

0.18 0.20 0.22 0.26 0.27 0.31 0.40 0.38 0.35 0.32 0.13 0.23

Ρ

0.12 0.16 0.20 0.18 0.23 0.19 0.22 0.32 0.27 0.25 0.16 0.54

Mg

0.43 0.85 0.91 0.65 0.54 0.23 0.72 0.49 0.57 0.75 0.50 1.25 0.49 0.67

2 3 46 65 34 46 407 553

Mo

22 21 43 21 29 12 21 38 32 32 7 20

m

Cu

58 54 40 30 56 37 51 116 59 78 36 184

PP

Zn

115 104 212 103 92 99 111 99 118 171 21 114

Μη

542 743 1510 701 659 293 880 738 861 1407 357 175

Fe

Quantities of Mineral Elements i n Tobacco and A l f a l f a Fibrous Residues and Wheat Bran.

Tobacco NC 95 NC 2326 Coker 139 Ky 171 Ky 151 Ky 16M Burley 21 Ky 14 Xanthi nc MD 609 Alfalfa Wheat bran

Fiber source

Table I I .


I

§"

g

M

X w w

00



258

Table I I I .

Fiber source

Tobacco NC 95 NC 2326 Coker 139 Ky 171 Ky 151 Ky 16 M Burley 21 Ky 14 Xanthi nc MD 609 Alfalfa Wheat bran LSD 0.05 LSD 0:01

Physical Properties of Tobacco and A l f a l f a Fibrous Residues and Wheat Bran.

Bulk volume (mL/9)

Water retention capacity (g water/g fiber)

Cation exchange capacity (meq NaOH/g) Χ 10"

14.90 11.33 14.77 14.87 14.00 13.80 13.97 14.80 16.33 13o23 9o47 4.53

9.57 8.40 10.40 7.40 10.86 9.18 8.47 8.55 8.02 9.13 4.92 1.18

21.83 17.50 21.50 20.00 19.00 20.67 21.50 18.50 15.67 19.67 15.33 6.17

0.93 1.25

0.89 1.21

2.47 5.43


2

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SHEEN AND SHEEN

Tobacco

Fiber

259

twice the volume of water than i t s a l f a l f a counterpart and s i x f o l d or more volume than wheat bran. The ranking of c a t i o n exchange c a p a c i t y among the f i b e r sources followed the same order of the above p h y s i c a l p r o p e r t i e s with tobacco f i b e r being the highest and wheat bran the l e a s t . The average value of c a t i o n exchange c a p a c i t y f o r tobacco c u l t i v a r s was 19.58 X 10"~ meq NaOH/g. The d i f f e r e n c e between tobacco f i b e r and wheat bran was about t h r e e - f o l d . The c a t i o n exchange c a p a c i t y of wheat bran was one-half the value of the a l f a l f a sample. Results of sodium taurocholate binding from two experiments employing d i f f e r e n t combinations of sodium taurocholate and f i b r o u s m a t e r i a l was given i n Table IV. There was a s i g n i f i c a n t d i f f e r e n c e among tobacco types but not w i t h i n a given type. Both experiments revealed that f l u e - c u r e d tobaccos had higher sodium taurocholate binding c a p a c i t y than the other tobacco types, and the binding amount was i n p r o p o r t i o n to the quantity of f i b e r . By averaging ten tobacco c u l t i v a r s , the binding capacity was 2.47 μ moles/50 mg and 6.07 μ moles/100 mg f o r two experiments. These values were ranked the highest, followed by a l f a l f a ; the lowest was wheat bran. The d i f f e r e n c e between the l a t t e r two was not s t a t i s t i c a l l y s i g n i f i c a n t . The f i b e r of flue-cured tobacco was s i g n i f i c a n t l y higher i n binding c a p a c i t y than a l f a l f a f i b e r and wheat bran i n most cases. However, the high binding c a p a c i t y of f l u e - c u r e d tobacco cannot be c o r r e l a t e d with the quantity of any chemical c o n s t i t u e n t s given i n Table I. Young tobacco p l a n t s u s u a l l y contain about 0.5% of dry wt as n i c o t i n e although n i c o t i n e quantity v a r i e s widely among genotypes (18). N i c o t i n e contamination i n tobacco f i b r o u s residue ranged from 180 to 340 ppm with a mean of 260+53 ppm (data not shown). Samples of Ky 171 f i b e r which contains 256 ppm of n i c o t i n e were repeatedly washed with c o l d water (1:10, w/v) and the washed residues were analyzed f o r n i c o t i n e quantity by GLC. On the average, each washing removed two-thirds the n i c o t i n e i n the residue; and a f t e r s e v e r a l washings, n i c o t i n e l e v e l approached 1 ppm (Figure 1). This p o i n t s to the f e a s i b i l i t y of lowering n i c o t i n e contamination i n the f i b r o u s residue to a n e g l i g i b l e l e v e l . The washing process d i d not a l t e r the concentration of p r o t e i n and n o n c e l l u l o s i c components.


2

Discussion P u r i f i e d p l a n t f i b e r s f o r d i e t a r y purposes are combinations of c e l l u l o s e , l i g n i n , h e m i c e l l u l o s e , gums and pectinaceous sub stances that exert chemical and p h y s i c a l a c t i o n s i n the g a s t r o i n t e s t i n a l t r a c t . D i e t a r y f i b e r complexes such as wheat bran contain not only the f i b e r components but a l s o other organic compounds that c o n t r i b u t e to n u t r i t i o n . In comparison to wheat bran, the d e p r o t e i n i z e d and d e c o l o r i z e d f i b e r complexes of tobacco and a l f a l f a have favorable chemical composition as d i e t a r y f i b e r s . T h e i r low concentrations i n s t a r c h and l i p i d s


UNCONVENTIONAL


260

Table IV.

SOURCES OF DIETARY FIBER

Binding In V i t r o of Sodium Taurocholate to Tobacco and A l f a l f a Fibrous Residues and Wheat Bran

Fiber source

Experiment 1 μ moles/50 mg

Tobacco NC 95 NC 2326 Coker 139 Ky 171 Ky 151 Ky 16M Burley 21 Ky 14 Xanthi nc MD 609 Alfalfa Wheat bran

3.65 3.30 2.78 1.89 1.91 2.12 1.86 2.54 2.48 2.21 2.16 2.09

7.89 7.13 7.88 6.44 4.78 6.56 4.37 4.99 5.14 5.56 4.93 4.84

0.88 1.20

1.83 2.49

LSD 0.05 LSD 0.01

Experiment 2 μ moles/100 mg



SHEEN AND SHEEN

Tobacco

Fiber

NUMBER OF WATER-WASHINGS

Figure 1. Effects of water-washing on the quantity of nicotine (O), protein (Ah and apparent hemicellulose (A) in the fibrous residue of Ky 171 tobacco.



262


and high amounts of c e l l u l o s i c components seem to make them more s u i t a b l e than wheat bran as l o w - c a l o r i e d i e t a r y f i b e r s . This i s f u r t h e r supported by the p h y s i c a l p r o p e r t i e s , e s p e c i a l l y f o r tobacco f i b e r , that a l a r g e bulk volume i n accompaniment with high water r e t e n t i o n and c a t i o n exchange c a p a c i t y would be d e s i r a b l e . In a d d i t i o n , the absorption of b i l e s a l t (sodium taurocholate) by fobacco f i b e r i s as e f f e c t i v e as, or more so than wheat bran which suggests that tobacco f i b e r may a l s o have the c a p a b i l i t y of r e g u l a t i n g serum c h l o r e s t e r o l l e v e l s . Nevert h e l e s s , the favorable chemical and p h y s i c a l p r o p e r t i e s of p l a n t f i b e r complex measured i n v i t r o s t i l l r e q u i r e confirmation from i n v i v o experimentation since the p h y s i o l o g i c a l performance and t e c h n o l o g i c a l f u n c t i o n a l i t y of d i e t a r y f i b e r i n f i b e r - e n r i c h e d foods are i n f l u e n c e d by many f a c t o r s . As suggested by Van Soest and Wine (10), the q u a n t i t a t i v e d i f f e r e n c e between NDF and ADF gives r i s e to a good estimation of h e m i c e l l u l o s e quantity, and ADF i s the sum of c e l l u l o s e and l i g n i n content. Taking wheat bran i n the present study (Table I) as an example, the c a l c u l a t e d values f o r h e m i c e l l u l o s e and ADF are 35.49 and 13.12 g/100 g,which are i n good agreement with Southgate's f i n d i n g s (19). However, the c a l c u l a t e d value of h e m i c e l l u l o s e i s almost 50% greater than that of apparent hemicellulose. This i s not s u r p r i s i n g since wheat bran i s r i c h i n s t a r c h known to contaminate the NDF f r a c t i o n . On the b a s i s of NDF and ADF q u a n t i t i e s , the c a l c u l a t e d value of h e m i c e l l u l o s e i n the a l f a l f a sample i s 11.13 g/100 g, while the average amount f o r tobacco f i b e r i s 9.96 + 2.82 g/100 g. The r e s p e c t i v e values of apparent h e m i c e l l u l o s e are 225% and 345% greater. I t has been reported that the ADF-reagent sometimes leaves s u b s t a n t i a l amounts of h e m i c e l l u l o s e i n the ADF-residue (20). Furthermore, Van Soest's detergent methods do not measure water-soluble components, whereas apparent h e m i c e l l u l o s e includes these substances i f they are not removed by 80% isopropanol washing. A l l these f a c t o r s can c o n t r i b u t e to the discrepancy between c a l c u l a t e d and apparent h e m i c e l l u l o s e values. This l e d to the suggestion that the pretreatment of f i b r o u s m a t e r i a l with l i p i d e x t r a c t i o n and p r o t e o l y t i c and a m y l o l y t i c enzymes would minimize erroneous r e s u l t s (19). One can a l s o a n t i c i p a t e d i f f e r e n c e s between tobacco and a l f a l f a and among tobacco c u l t i v a r s i n chemical composition and s t r u c t u r e v a r i a t i o n of c e l l w a l l as w e l l as the nature of complex formation i n v o l v i n g c e l l w a l l c o n s t i t u e n t s and other substances. I t would be h i g h l y d e s i r a b l e to compare the sugar c o n s t i t u e n t s of tobacco f i b e r components with those of conventional d i e t a r y f i b e r s . The high concentration of i r o n and calcium i n tobacco f i b e r would be d e s i r a b l e from a n u t r i t i o n a l viewpoint. The b i o a v a i l a b i l i t y of mineral elements i n d i e t a r y f i b e r s has been discussed i n the l i t e r a t u r e (16). Aside from f i b e r per se, p h y t i c a c i d was found to be the major determinant of b i v a l e n t metal d e f i c i e n c i e s (21). Phytate content i s high i n wheat bran and other



18.

SHEEN AND SHEEN

Tobacco

Fiber

263

d i e t a r y f i b e r s of seed o r i g i n since i t i s a source of g l u c u r o nate precursor f o r synthesis of c e l l w a l l polysaccharides during germination (22). Among the hundreds of compounds i n tobacco l e a f , phytate has never been mentioned i n a l a r g e volume of tobacco l i t e r a t u r e s (18). In analogy to phytate i n wheat bran, tobacco p l a n t s accumulate 2 to 5% of dry weight as o x a l i c a c i d , predominately i n the form of calcium s a l t , i n mature leaves (18). Calcium oxalate i s i n s o l u b l e i n water. Young p l a n t s of seven b u r l e y c u l t i v a r s under high d e n s i t y growth had oxalate content i n the range of 0.6 to 1.4% (23). The d i e t a r y intake of oxalate poses a concern f o r calcium and magnesium a v a i l a b i l i t y although i t was documented that oxalate can be formed i n v i v o from d i e t s containing ascorbate, g l y c i n e , g l y c o l a t e , and g l y o x y l a t e (24). Oxalate content i n tobacco f i b e r was not determined i n the present study. However, the d e p r o t e i n i z a t i o n and d e c o l o r i z a t i o n processes would remove s o l u b l e o x a l a t e . Calcium oxalate may remain i n the f i b r o u s residue.and w i l l not f u r t h e r deplete calcium i n d i e t s because o x a l i c a c i d i s already bound to calcium. Many e d i b l e p l a n t s are r i c h i n o x a l i c a c i d . For example, s p i n ach contains 8 to 10% dry weight as o x a l i c a c i d (25). F i v e cups of t e a per day i n the E n g l i s h d i e t c o n t r i b u t e s to an intake of 75 mg o x a l i c a c i d (26). Oxalate content i n tobacco f i b e r i s probably i n the same range as that of c e r t a i n common f o o d s t u f f s . Another concern of p o s s i b l e adverse e f f e c t s of tobacco f i b e r complex as d i e t a r y f i b e r i s n i c o t i n e contamination. Nico t i n e i s regarded as h i g h l y t o x i c . Gasseline et al (27) r e ported that the o r a l LD5Q of an a d u l t human has been estimated to be 30 to 60 mg (0.5 to 1.0 mg/kg body wt). They also s t a t e d that tobacco i s much l e s s t o x i c than expected from i t s n i c o t i n e content because i n t e s t i n a l absorption of n i c o t i n e as present i n tobacco i s so slow that metabolic i n a c t i v a t i o n sometimes keeps pace with absorption and the e l i m i n a t i o n of n i c o t i n e i s completed w i t h i n 16 hours. About 80 to 90% of the n i c o t i n e i n human u r i n e has already been d e t o x i f i e d . Since n i c o t i n e i s very waters o l u b l e , the washing of tobacco f i b r o u s residue could lower n i c o t i n e to a n e g l i g i b l e l e v e l as demonstrated i n the present study. I f the water-washed tobacco f i b e r contains 10 ppm of n i c o t i n e , a 10% i n c o r p o r a t i o n i n f i b e r - e n r i c h e d formulation r e s u l t s i n 1 ppm of n i c o t i n e i n the formulated foods. The presence of n i c o t i n e i n minute q u a n t i t i e s was reported i n tomato and other solanaceous vegetables (28). With the GLC method employing an a l k a l i n e flame i o n i z a t i o n detector (6), a broad array of f r e s h and preserved foods was analyzed f o r n i c o t i n e contamination. N i c o t i n e was detected at 2 to 15 ppm (on a dry wt b a s i s ) i n tomato, potato, eggplant, and green pepper but not i n a l f a l f a and wheat bran. Most i n t e r e s t i n g i s the f i n d i n g of n i c o t i n e i n t e a , e x p e c i a l l y i n s t a n t t e a , at l e v e l s of 15-24 ppm. N i c o t i n e q u a n t i t y i n tobacco can be d r a s t i c a l l y lowered by genetic means (29). V a r i e t a l d i f f e r e n c e i n oxalate content i n



264


tobacco l e a f a l s o i n d i c a t e s p o s s i b l e genetic r e g u l a t i o n (23). I f tobacco i s grown as a food crop, the concentration of these undesirable l e a f c o n s t i t u e n t s can be lowered by means of breed ing. The p o t e n t i a l of tobacco u t i l i z a t i o n as a source of s o l u b l e p r o t e i n s and the d e p r o t e i n i z e d residue derived from the p r o t e i n e x t r a c t i o n process as animal feed and s a f e r smoking m a t e r i a l has been mentioned i n recent years (_5, 6^, 3Q). The present study suggests that a f t e r d e c o l o r i z a t i o n tobacco f i b r o u s residue may be a p o t e n t i a l source of d i e t a r y f i b e r . A d d i t i o n a l research i s c e r t a i n l y needed to evaluate the n u t r i t i o n a l and p h y s i o l o g i c a l s i g n i f i c a n c e of tobacco f i b e r i n experimental animals. Some of these s t u d i e s are p r e s e n t l y being undertaken. Acknowledgments The i n v e s t i g a t i o n report i n t h i s paper (82-11-63) was i n connection with a p r o j e c t of the Kentucky A g r i c u l t u r a l Experiment S t a t i o n , Lexington, Kentucky, and i s published with the approval of the D i r e c t o r . The authors are g r a t e f u l to the A n a l y t i c a l Laboratory of the Agronomy Department, U n i v e r s i t y of Kentucky f o r performing the q u a n t i t a t i o n of mineral elements. Literature Cited 1.

2.

3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.

B u r k i t t , D. P. "Dietary f i b r e : current developments of importance to h e a l t h " ; Heaton, K. W., Ed.; Technomic P u b l i s h i n g Company, Inc.: Westport, CT. 1979, pp. 35-44. Heaton, K. W. "Dietary f i b r e : current developments of importance to h e a l t h " ; Technomic P u b l i s h i n g Company, Inc.: Westport, CT. 1979, p. 158. I n g l e t t , G. E.; Falkehag, S. I. "Dietary f i b e r s : chemistry and n u t r i t i o n " ; Academic Press: New York, 1979, p. 285. Anderson, J . W. Cereal Foods World 1977, 22, 12-15. Wildman, S. G. Crops and S o i l Magazine; January, 1979, pp. 7-9. Sheen, S. J . B e i t r . Tabakforsch. I n t r . 1982, i n press. Hamilton, J . L.; Lowe, R. H. Tob. S c i . 1978, 22, 89-93. Gaines, T. P.; Meudt, W. J . Tob. S c i . 1968, 12, 13O-133. Bacot, A. M. U.S.D.A. T e c h n i c a l B u l l e t i n No. 1225, 1960, p. 126. Van Soest, P. J . ; Wine, R. H. J . Assoc. O f f . Anal. Chem. 1967, 50, 50-55. F i s k e , C. H.; Subbarow, Y. J . B i o l . Chem. 1925, 66, 375-400. E i v a z i , F.; Sims, J . L.; C r u t c h f i e l d , J . Comm. S o i l S c i . Plant Anal. 1982, 13, 135-150. Montgomery, M. J . ; Baumgardt, B. R. J . Dairy S c i . 1965, 48, 1623-1628. McConnell, Α. Α.; Eastwood, Μ. Α.; M i t c h e l l , W. D. J . S c i . Food A g r i c . 1974, 20, 1457-1464.


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Fiber

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K r i t c h e v s k y , D.; Story, J . A. J . Nutr. 1974, 104, 458-462. Reinhold, J . G. "Proc. 9th I n t . Cong. Nutr."; Chavez, Α.; Bourges, H.; Basts, S.; Eds.: Karger: B a s e l , 1975, pp. 98-105. Rasper, V. F. " D i e t a r y f i b e r s : chemistry and n u t r i t i o n " ; I n g l e t t , G. E.; Falkenhag, S. I . , Eds.; Academic Press: New York, 1979, pp. 93-115. Tso, T. C. "Physiology and biochemistry of tobacco p l a n t s " ; Dowdes, Hutchinson and Ross, Inc.: Stroudsburg, PA. 1972, p. 393. Southgate, D. A. T. " D i e t a r y fibre: current developments of importance to h e a l t h " ; Heaton, K. W., Ed.; Technomic P u b l i s h i n g Company, Inc.: Westport, CT. 1979, pp. 9-19. Theander, 0.; Aman, P. " D i e t a r y fibers: chemistry and n u t r i t i o n " ; I n g l e t t , G. E.; Falkehag, S. I . , Eds.; Academic Press: New York, 1979, pp. 215-244. Maga, J . A. J . A g r i . Food Chem. 1982, 30, 1-9. Matheson, Ν. K.; St. Clair, M. Phytochem. 1971, 10, 12991302. Brumagen, D. M.; H i a t t , A. J . Plant and S o i l 1966, 24, 239249. Rodricks, J . W.; Pohland, A. E. "Food s a f e t y " ; Roberts, Η. R., Ed.; John Wiley and Sons: New York, 1981, pp. 181-237. Regan, W. S.; Lambeth, V. N.; Brown, J . R.; B l e v i n s , D. G. Am. Soc. Hort. S c i . 1968, 93, 485-492. Zarembski, P. M.; Hodgkinson, A. B r i t . J . Nutr. 1962, 16, 627-634. G o s s e l i n , R. E.; Hodge, H. C.; Smith, R. P.; Gleason, M. N. " C l i n i c a l t o x i c o l o g y of commercial products, acute poisoning"; 4th ed.; The Williams and W i l k i n s Co.: Baltimore, 1976, pp. III-1-323. Mothes, H. K.; Schutte, H. R. " B i o s y n t h e s i s der A l k a l o i d e " , Deutscher V e r l a g der Wissenschaften VEB:Berlin, 1969, p. 730. Legg, P. D.; C h a p l i n , J . F.; C o l l i n s , G. B. J . H e r e d i t y , 1969, 60, 213-217. Sheen, S. J . ; Lowe, R. H.; Burton, H. R. B e i t r . Tabakforsch. I n t r . 1982, 11, 170-179.

RECEIVED January 11,

1982


Unconventional Sources of Dietary Fiber - American Chemical Society

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