Unconventional Sources of Dietary Fiber - American Chemical Society

16 Cellulose, Xylan, Corn Bran, and Pectin in the Human Digestive Process A L F R E D C. OLSON, GREGORY M. GRAY, and MEI-CHEN CHIU

Downloaded by UNIV OF ARIZONA on December 4, 2012 | http://pubs.acs.org Publication Date: April 11, 1983 | doi: 10.1021/bk-1983-0214.ch016

U.S. Department of Agriculture, Western Regional Research Center, Berkeley, CA 94710 SHARON E. FLEMING University of California, Department of Nutrition, Berkeley, CA 94710

Acid hydrolysis of human fecal samples collected after ingestion of different dietary fibers produced monosaccharides that were related to the fibers ingested. Dietary fibers studied in five normal male subjects were cellulose, xylan, corn bran and pectin. Increases in monosaccharides in recovered hydrolyzed feces from fiber diets compared to those from the fiber-free diet were: galactose for the pectin diet; xylose and glucose for the cellulose diet; xylose and mannose for the xylan diet; and arabinose, xylose, galactose and glucose for the corn bran diet. Comparison of the fecal results to those for the intact food fibers showed that fermentation of fiber components in the colon was different for each fiber. Dietary f i b e r i s o f t e n considered i n terms of i t s physiol o g i c a l e f f e c t s i n man. I t has been defined as that p o r t i o n of plant foods r e s i s t a n t to h y d r o l y s i s by the alimentary enzymes of man (1) and as the i n d i g e s t i b l e m a t e r i a l i n the d i e t derived mainly from plant c e l l w a l l s , i n c l u d i n g the sum of the polysaccharides and l i g n i n i n the d i e t that are not digested by the endogenous s e c r e t i o n s of the lumen of the d i g e s t i v e t r a c t ( 2 ) . In a d d i t i o n to these p h y s i o l o g i c a l d e f i n i t i o n s a p h i l o s o p h i c a l one has been proposed which s t a t e s that d i e t a r y f i b e r includes a l l components of the d i e t which are imagined to pass through the small i n t e s t i n e s u b s t a n t i a l l y unchanged ( 3 ) . I t i s also not a s i n g l e substance, nor i s i t i n e r t , i n d i g e s t i b l e m a t e r i a l which simply passes through the human gut ( 4 ) . Thus plant gums and mucilages are not c e l l w a l l components but are polysaccharides r e l a t e d i n chemical s t r u c t u r e and p r o p e r t i e s to c e l l w a l l c o n s t i t u e n t s and not hydrolyzed by the human g a s t r o i n t e s t i n a l enzymes. These m a t e r i a l s are o f t e n i n the d i e t as emul-

This chapter not subject to U.S. copyright. Published 1983, American Chemical Society

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


222

UNCONVENTIONAL SOURCES OF DIETARY FIBER

s i f i e r s , v i s c o s i t y agents and s t a b i l i z e r s and not recognized as d i e t a r y f i b e r per se. This broad understanding of d i e t a r y f i b e r makes i t d i f f i c u l t to describe or c h a r a c t e r i z e chemically and to e l u c i d a t e i t s behavior i n the g a s t r o i n t e s t i n a l t r a c t . Nevertheless with changing d i e t a r y habits and recommendations f o r food intake f o r good h e a l t h and n u t r i t i o n , i t i s important that the chemistry of t h i s c l a s s of food components be more r e a d i l y c h a r a c t e r i z e d and understood. Since much d i e t a r y f i b e r i s of c e l l w a l l o r i g i n , some of the approaches that have been s u c c e s s f u l l y used t o d e f i n e and e x p l a i n the chemistry of plant c e l l walls (5, _6) should be a p p l i c a b l e to research on the c h a r a c t e r i z a t i o n and f u n c t i o n of d i e t a r y f i b e r (7, 9 ) . To t h i s end we have i n v e s t i g a t e d s e v e r a l d i e t a r y f i b e r s derived from plant cell w a l l s both before and a f t e r complete passage through the human gastrointestinal tract. Plant c e l l w a l l s are chemically complex and many of the components we are p r i m a r i l y i n t e r e s t e d i n are b a s i c a l l y i n s o l uble. These two f a c t s have hampered s t r u c t u r a l studies on plant c e l l w a l l s as w e l l as studies designed to determine what these substances do i n the g a s t r o i n t e s t i n a l t r a c t . Thus, f o r example, i n order to study the chemistry of i n d i v i d u a l components of the c e l l w a l l they must be s o l u b i l i z e d and p u r i f i e d , a task that i s d i f f i c u l t to do without p h y s i c a l l y or chemically a l t e r i n g the components. In t h i s study we have i n v e s t i g a t e d those portions of s e v e r a l c e l l w a l l derived d i e t a r y f i b e r s that are s u s c e p t i b l e to h y d r o l y s i s i n t r i f l u o r o a c e t i c a c i d (TFA). D i e t a r y f i b e r s with s i g n i f i c a n t l y d i f f e r e n t compositions of a c i d hydrolyzable n e u t r a l monosaccharides were used i n the study. They were a c e l l u l o s e , a xylan, a corn bran and a p e c t i n . Monosaccharides released by d i r e c t a c i d h y d r o l y s i s of the d i e t a r y f i b e r s were determined before consumption by human subjects and compared to the monosaccharides released by d i r e c t a c i d hydrolys i s of f e c a l m a t e r i a l r e s u l t i n g from i n g e s t i o n of each f i b e r and of f e c a l m a t e r i a l from the subjects on a f i b e r f r e e d i e t . Those portions of d i e t a r y f i b e r that d i d not survive the g a s t r o i n t e s t i n a l t r a c t were e i t h e r digested and absorbed i n the small i n t e s t i n e or were l i k e l y n u t r i t i o n a l substrates f o r i n t e s t i n a l m i c r o f l o r a growth and the production of m i c r o f l o r a by-products. These include v o l a t i l e f a t t y acids (VFA's) that can be absorbed and u t i l i z e d by the host (10, 11) and the gases, carbon d i o x i d e , hydrogen and sometimes methane (12^, 13). This study i s part of a continuing i n v e s t i g a t i o n of the r e l a t i o n s h i p between d i e t a r y f i b e r sources and b i o a v a i l a b i l i t y of n u t r i e n t s . S p e c i f i c o b j e c t i v e s of t h i s research were to i n v e s t i g a t e chemical d i f f e r e n c e s of various sources of e d i b l e f i b e r and to determine the e f f e c t s of the human g a s t r o i n t e s t i n a l t r a c t on these f i b e r sources.


16.

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Cellulose,

Xylan,

Corn Bran,

and

Pectin

223


Experimental The design f o r the feeding p o r t i o n of the experiment i s described by Marthinsen and Fleming ( 1 4 ) . B r i e f l y , s i x normal healthy male v o l u n t e e r s , 21-35 years o l d with no h i s t o r i e s of g a s t r o i n t e s t i n a l d i s o r d e r s or food a l l e r g i e s , were s e l e c t e d f o r the study. I n i t i a l l y , subjects were provided with a n u t r i t i o n a l l y adequate blended-food d i e t on an o u t p a t i e n t b a s i s f o r two weeks. Once subjects took up residence i n the metabolic u n i t they undertook a s t r i c t daily regime. The 63-day metabolic study was d i v i d e d i n t o seven metabolic p e r i o d s , each of nine days d u r a t i o n (Table I ) . A l l s u b j e c t s r e c e i v e d the b a s a l , f i b e r - f r e e d i e t during the f i r s t metabolic p e r i o d . The subsequent t e s t d i e t sequence was designed to minimize d u p l i c a t i o n of any previous d i e t e f f e c t s (Table I ) . D i e t s i n c l u d e d two bland formulations p r o v i d i n g e i t h e r 100% or 85% of the d a i l y energy requirements f o r the i n d i v i d u a l . Four d i e t s contained f i b e r sources i n c l u d i n g a c e l l u l o s e ( A l p h a c e l from ICN Pharm a c e u t i c a l s , I n c . ) , a p e c t i n (from Sigma Chem. Co.), a x y l a n (from ICN Pharmaceuticals), and a raw corn bran (from Quaker Oats). The b a s a l f o r m u l a t i o n provided 0.8g protein/kg body weight d a i l y from egg albumin (Seymour Foods, I n c . ) . Fat ( b u t t e r f a t and cottonseed o i l ) provided 30% of the c a l o r i c r e q u i r e ments and the remainder was provided by c o r n s t a r c h (CPC I n t e r n a t i o n a l ) , dextromaltose (American Maize Products Co.) and sucrose i n a r a t i o of 5:5:1. D a i l y supplements of v i t a m i n s , m i n e r a l s , and c h o l i n e were taken. During the t e s t , d i e t a r y f i b e r was provided with each meal. A l p h a c e l , x y l a n , and p e c t i n were fed at 0.5g/kg body weight per day. Corn bran was considered to be approximately 80% d i e t a r y f i b e r and was f e d at 0.6g/kg body weight. Each f i b e r was consumed as a pudding c o n t a i n i n g other d i e t a r y constituents. The remaining d i e t a r y c o n s t i t u e n t s were consumed as a milkshake s t y l e d r i n k . Feces were c o l l e c t e d d a i l y , f r o z e n , compiled i n t o t h r e e day pools, d i l u t e d with water and homogenized using an e l e c t r i c colloid mill. Homogenates were kept f r o z e n p r i o r to removing aliquots for analysis. Pooled c o l l e c t i o n s from days 7-9 f o r each d i e t were used f o r the analyses except f o r subject #5 on the x y l a n d i e t where the c o l l e c t i o n from days 4-6 was used because of the l o s s of the 7-9 day sample. Dry weights were obtained by d r y i n g a l i q u o t s under vacuum at 70°C f o r 16 hours. Hydrolyses were performed f o l l o w i n g the procedures of A l bersheim et a l (15) f o r the c h a r a c t e r i z a t i o n of plant p o l y s a c c h a r i d e s and described by us e a r l i e r f o r the h y d r o l y s i s of dietary fiber samples (16). For these fiber samples 2-6mg were hydrolyzed i n 1ml of 2N TFA at 121°C f o r 1 hour. Fecal samples contained other components i n a d d i t i o n to the p o l y s a c charides or polysaccharide residues from the ingested food f i ber so that a l i q u o t s f o r the hydrolyses were increased to 10-25mg



85% Energy Corn bran

Xylan Cellulose Pectin

Basal Pectin Corn bran 85% Energy Xylan Cellulose

Corn bran Cellulose Pectin Basal 85% Energy Xylan

Pectin 85% Energy Xylan Cellulose Basal Corn bran

Xylan

Basal

Cellulose

Pectin

Corn bran

85% Energy

Cellulose

Xylan

85% Energy

Corn bran

Pectin

Basal

II

III

IV

V

VI

VII

Basal

Basal

Basal

Basal

Basal

Basal

Basal

I

6

_5

_4

3

2

Subject

Diet

DIETARY SCHEME FOR SUBJECTS

J.

Metabolic Period

Table I .



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Cellulose,

Xylan,

Corn Bran, and Pectin

225

(dry weight). TFA was evaporated and the sugars reduced with sodium borohydride. Excess sodium borohydride was destroyed with a c e t i c a c i d and borate was removed with methanol. The a l d i t o l s were converted to the corresponding acetates by adding lml of a 10:1 a c e t i c anhydride/pyridine s o l u t i o n and heating at 121°C f o r 2 hours. The acetates were q u a n t i t a t i v e l y separ ated by i n j e c t i n g Ιμΐ of the r e a c t i o n mixture onto a 1/8" X 6' s t a i n l e s s s t e e l column packed with Supelco 2330 using 25 ml/min He as c a r r i e r gas and a FID d e t e c t o r . The oven was programmed from 200-224°C. The gas chromatograph u n i t was a Hewlett Packard 5880 L e v e l 3. Mixtures of known sugars were reduced and a c e t y l a t e d to serve as standards. Samples were analyzed i n t r i p l i c a t e and the r e s u l t s averaged. Results And D i s c u s s i o n D i e t a r y F i b e r . A c i d s t r e n g t h , temperature, time, and amount of sample per ml of a c i d s o l u t i o n a l l i n f l u e n c e the amounts of monosaccharides produced on h y d r o l y s i s . From the r e s u l t s of pre l i m i n a r y s t u d i e s c o n d i t i o n s were s e l e c t e d f o r these hydrolyses which appeared to produce c l o s e to maximum amounts of each monosaccharide. A l l of the hydrolyses were conducted f o l l o w i n g the same procedure. We have p r e v i o u s l y shown that d i f f e r e n t d i e t a r y f i b e r s are composed of s i g n i f i c a n t l y d i f f e r e n t comple ments of a c i d hydrolyzable n e u t r a l monsaccharides as determined by d i r e c t TFA h y d r o l y s i s (16). Not only d i d d i f f e r e n t d i e t a r y f i b e r s g i v e d i f f e r e n t r e s u l t s but d i f f e r e n t l o t s of the same f i b e r type gave d i f f e r e n t r e s u l t s . TABLE I I COMPOSITION OF DIETARY FIBERS BY TFA HYDROLYSIS AS PERCENT OF ORIGINAL MATERIAL

Fiber

Rham

Arab

Alphacel

0

0

Xylan

0

0.20

Pectin

1.0

1.2

Corn bran

0.1

13

Xyl 4.6 25 0.1 24

Mann

Gal

Glu 6.3

0

0

39

0

13

0

2.0

0

0

3.4

20

The composition of d i e t a r y f i b e r s f e d i n termined by TFA h y d r o l y s i s are shown i n Table contained 11% hydrolyzable sugars, the xylan bran 60%. The small amount of xylose recovered i s most l i k e l y from h e m i c e l l u l o s e present i n

t h i s study as de I I . The A l p h a c e l 77% and the corn from the A l p h a c e l the o r i g i n a l wood


226

UNCONVENTIONAL

SOURCES OF DIETARY

FIBER


from which the A l p h a c e l was prepared. The xylan was r e p o r t e d l y from larchwood. The p r i n c i p l e recovered sugars from the xylan were mannose, xylose and glucose i n that order. The mannose to glucose r a t i o of 3 suggested the presence of a glucomannan, a h e m i c e l l u l o s e found i n wood. The f r e e glucose content of the f i b e r was l e s s than 0.1% ( d r y weight b a s i s ) as determined by water e x t r a c t i o n and Statzyme a n a l y s i s (Worthington Diagnostics) f o r glucose. Eighty percent of the glucose recovered from the corn bran was s t a r c h as determined by amyloglucosidase hydrol y s i s followed by a n a l y s i s f o r glucose. P e c t i n contained small amounts of rhamnose, arabinose and galactose as expected. Subject Responses. E a r l y i n the study subject #4 dropped out and was not replaced. In the f o l l o w i n g presentation and d i s c u s s i o n of data r e s u l t s from subject #6 are sometimes q u i t e d i f f e r e n t from those of the other subjects although i n most cases d i r e c t i o n a l l y c o n s i s t e n t . No explanation for this i s o f f e r e d at t h i s time. E v a l u a t i o n of the 100% and 85% energy d i e t s w i l l be made at a l a t e r time. E x c r e t i o n of breath and f l a t u s gases by the subjects has been reported (14). F e c a l Hydrolyses. The rhamnose, arabinose, xylose, mannose, g a l a c t o s e and glucose from TFA h y d r o l y s i s of a l i q u o t s of the 3-day f e c a l samples f o r each subject on each d i e t sequence are shown i n Figures 1-5. For subject #1 (Figure 1) on the f i b e r f r e e d i e t , small amounts of a l l of the sugars were produced on h y d r o l y s i s of the f e c a l sample. F e c a l m a t e r i a l from t h i s subject on the A l p h a c e l d i e t gave more glucose, on the xylan d i e t more x y l o s e , on the corn bran d i e t more arabinose, xylose, galactose and glucose, and on the p e c t i n d i e t more rhamnose and galactose. S i m i l a r r e s u l t s were observed f o r subjects 2, 3, 5, and 6 (Figures 2-5). For every subject the amounts of the sugars produced on a c i d h y d r o l y s i s of feces were d i f f e r e n t f o r each d i e t f e d and were r e l a t e d to the s p e c i f i c f i b e r f e d . Comparison of r e s u l t s from the s e v e r a l f i b e r - f r e e d i e t s run i n each sequence showed d i r e c t i o n a l increases i n hydrolyzable monosaccharides i n the feces which appear to be r e l a t e d to immediate d i e t h i s t o r y . The amount of hydrolyzable glucose i n feces f o l l o w i n g the A l p h a c e l d i e t s was more than could be accounted f o r i f a l l of the A l p h a c e l had been excreted, assuming the same amount of glucose was produced as that from the o r i g i n a l A l p h a c e l . Further examination of the samples showed that they contained both f r e e glucose and s t a r c h . Free glucose was estimated by analyzing water e x t r a c t s f o r glucose by both the Statzyme procedure (Worthington D i a g n o s t i c s ) and gas chromatography of the a l d i t o l acet a t e s . Starch was estimated by treatment of autoclaved fecal samples with amyloglucosidase f o r 3 hours at 55°C followed by the same analyses f o r glucose. In feces from the A l p h a c e l d i e t s f r e e glucose accounted f o r 5-15% and glucose from s t a r c h ranged from 15-25% of the t o t a l glucose recovered f o l l o w i n g TFA hydro-



>

co

2

FIBER FREE 100% ENERGY ALPHACEL

s

M XYLAN

FIBER FREE 85 % ENGERGY

R IA X M j G a Gl]

CORNBRAN

4&

PECTIN

FIBER FREE 100% ENERGY

Figure 1. Monosaccharides from the hydrolysis of aliquots of 3-day fecal collections for Subject 1 on the indicated diets. Key: R, rhamnose; A, arabinose; X, xylose; M, mannose; Ga, galactose; and Gl, glucose.

1000

2000 Η

3000 Η

4000-1 g

5000 -|

J8

6000-1

7000-1

8000·



Ο

Û

Ο


FIBER FREE REE 100% ENERGY

PECTIN

CORNBRAN COI

xlMio.joil

4

FIBER FREE 8 5 % ENERGY

XYLAN

JJL ALPHACEL

Monosaccharides from the hydrolysis of aliquots of 3-day fecal collections for Subject 5 on the indicated diets. Key is the same as in Figure 1.

FIBER FREE 100% ENERGY

f

t oc u

III

ο

Figure 4.

1000H

2000-1

3000-

4000H

5000-1

6000-1

7000-1

8000-1



FIBER FREE 85 % ENERGY CORNBRAN CORNBRAN

1

0

0

%

F , B E R

J3i E

N

E

R

FREE

O

Y

XYLAN

ALPHACEL

K|A

PECTIN

Χ M [Go Gil

Monosaccharides from the hydrolysis of aliquots of 3-day fecal collections for Subject 6 on the indicated diets. Key is the same as in Figure 1.

NO SAMPLES

Figure 5.

looo H

2000H

3000H

4000H co

S

500θΗ Ο

6000-H

70004

8000



232

UNCONVENTIONAL SOURCES OF DIETARY FIBER

lysis. This p a r t i a l l y accounted f o r the l a r g e amount of glucose recovered from t h i s d i e t . However, s i m i l a r amounts of f r e e g l u cose and s t a r c h were a l s o found i n f e c a l samples from the corn bran d i e t while smaller amounts were found i n the f e c a l samples from the other d i e t s i n c l u d i n g the f i b e r - f r e e d i e t s . While d i f f i c u l t i e s i n these analyses prevented better quantitation, the r e s u l t s suggest that both A l p h a c e l and corn bran may have i n h i b i t e d s t a r c h d i g e s t i o n . This may be p a r t i a l l y due to b u l k i n g e f f e c t and l e s s e f f e c t i v e substrate/enzyme i n t e r a c t i o n . Small amounts of glucose were produced from c e l l u l o s e prep a r a t i o n s by h y d r o l y s i s with TFA as already noted (Table I I ) and reported by others (19). The amount produced probably depends on the p h y s i c a l form of the c e l l u l o s e since d i f f e r e n t amounts were obtained from d i f f e r e n t preparations. Subtracting the amounts of f r e e glucose and that derived from s t a r c h from the t o t a l amount obtained by d i r e c t TFA-hydrolysis of feces from some of the A l p h a c e l d i e t s s t i l l leaves more glucose than can be accounted f o r from unchanged c e l l u l o s e i t s e l f . This suggests that passage through the g a s t r o i n t e s t i n a l t r a c t may have produced changes that made c e l l u l o s e i n recovered feces more s u s c e p t i b l e to TFA h y d r o l y s i s than that which was f e d . Xylan and Corn Bran. The xylan and corn bran f i b e r s were mainly h e m i c e l l u l o s e and contained more complex mixtures of hydrolyzable monosaccharides than the other f i b e r sources. It was of some i n t e r e s t to consider the r e s u l t s from the h y d r o l y s i s of f e c a l samples from these d i e t s i n an a l t e r n a t e manner. The data were r e p l o t t e d to show monosaccharides recovered as percent of the amount f e d f o r each s u b j e c t . ( F i g u r e s 6 and 7 ) . For comp a r i s o n the composition of the o r i g i n a l f i b e r i s shown on the extreme l e f t as percent dry weight of the f i b e r . As already noted the composition of the x y l a n was i n t e r e s t ing because of i t s high mannose and glucose content, suggesting the presence of glucomannan i n the x y l a n . The feces examined f o r hydrolyzable polysaccharides showed that the mannose ( o r mannan) was h i g h l y fermentable s i n c e only 0-3% of i t survived to be excreted. S i m i l a r l y l e s s than 10% of the glucose o r i g i n a l l y present i n the xylan ingested was recoverable by h y d r o l y s i s of f e c a l samples. Over 70% of the xylose i n the xylan a l s o d i s a p peared. Thus, the o r i g i n a l xylan may be composed of at l e a s t two r e a d i l y fermentable p o l y s a c c h a r i d e s , a xylan (31-4 l i n k e d xylose u n i t s ) and a glucomannan (31-4 l i n k e d mannose and g l u cose i n the r a t i o 3:1). Of the two polysaccharides the g l u c o mannan was more r e a d i l y fermentable s i n c e l e s s of i t s u r v i v e d the d i g e s t i v e process. Corn bran has a l a r g e xylose to arabinose r a t i o of 1.8. Recovery of these sugars i n the feces was the highest of any of the f i b e r s f e d . The xylose to arabinose r a t i o was a l s o c l o s e to that i n the bran f e d , ranging from 1.5-1.7. Galactose, while i n q u i t e small amounts, survived i n roughly the same



Figure 6.

5Η

ιοΗ

15Η

20Η

25Η

30-Η

35Η

40%-ι

6

SUBJECT *

1

M GI

2

3

5

6

Recovery of monosaccharides from xylan diets from each subject as percent of amount fed. Composition of fiber fed is shown at left.

= 0

Μ ·


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

1

1.6

X|G»]Cl|

xpJoi

ί αa .

Figure 7. Recovery o/ monosaccharides from corn bran diets from each subject as percent of amount fed. Composition of fiber fed is shown at left.

20·

30Η

40·

50H

60H

70H

80-1


Η

w

ο

ο d ** Ο m

>

δ

Η

8 < w

Κ)


16.

OLSON ET AL.

Cellulose,

Xylan,

Corn Bran, and Pectin

235

proportions. The glucose value of 20% f o r the corn bran i n cludes 16% s t a r c h and, by d i f f e r e n c e , 4% of the glucose is probably t i e d up i n h e m i c e l l u l o s e . Then a c a l c u l a t e d value of hydrolyzable glucose i n the feces based only on glucose i n h e m i c e l l u l o s e i n the o r i g i n a l f i b e r would be 4X that shown i n F i g u r e 7. Comparison of these two sources of hemicellulose i n the d i e t s and t h e i r r e c o v e r i e s i n the feces i n d i c a t e d that t h e i r behavior i n the g a s t r o i n t e s t i n a l t r a c t may depend both on t h e i r composition and p a r t i c l e s i z e . The xylan was a f i n e l y d i v i d e d preparation while the corn bran was composed of much l a r g e r particles. Very l i t t l e of the xylan was recovered i n the feces compared to that recovered from the corn bran. F i b e r Input; F e c a l Output. F e c a l output on a f i b e r - f r e e d i e t may i n c l u d e b a c t e r i a l d e t r i t u s , b i l e s a l t s , mucus, i n t e s t i n a l w a l l c e l l d e b r i s , and perhaps f i b e r type m a t e r i a l i n the " f i b e r - f r e e " d i e t that i s as yet not recognized as such ( e . g . m a t e r i a l added as e m u l s i f i e r s , e t c ) . F e c a l output from a f i b e r supplemented d i e t minus that from the f i b e r - f r e e output should i n d i c a t e the extent of the f i b e r i t s e l f that was excreted plus the i n c r e a s e i n b a c t e r i a l d e t r i t u s , mucus and other m a t e r i a l perhaps rendered l e s s d i g e s t i b l e due to the presence of the fiber. In Figure 8 the amount of each f i b e r consumed i s shown compared to a corrected average (of the f i v e subjects) t o t a l 3-day dry weight of f e c a l output and amounts of TFA hydrolyzable sugars present. The c o r r e c t i o n was made by s u b t r a c t i n g the average f e c a l output and hydrolyzable sugars (shown i n the ex treme r i g h t i n F i g u r e 8) obtained from the f i b e r - f r e e d i e t s from the values obtained on the f i b e r d i e t s . Average f e c a l outputs f o r a l l of the f i b e r d i e t s are l a r g e r than those from f i b e r - f r e e d i e t s . Most of the TFA-hydrolyzable sugars from the p e c t i n and xylan f i b e r s are not recovered i n the feces (9, Γ 7 , 18). Both the A l p h a c e l and corn bran d i e t s produced l a r g e increases i n f e c a l dry weights. For corn bran r e l a t i v e l y s i m i l a r proportions of x y l o s e , arabinose and galactose found i n the bran were found i n the f e c e s . The l a r g e bran p a r t i c l e s and the chemical form of the polysaccharides probably l i m i t s the f e r m e n t a b i l i t y of these hemicelluloses (20, 21). I t was pos s i b l e to v i s u a l l y i d e n t i f y corn bran p a r t i c l e s i n f e c a l m a t e r i a l . S t a t i s t i c a l A n a l y s i s . Means and 95% confidence intervals were c a l c u l a t e d for the recovered monosaccharides (Table I I I ) . Data was t r e a t e d by a n a l y s i s of variance f i t t i n g d i e t s and sub jects. In some cases transformations were needed to s t a b i l i z e the variances between d i e t s . Significant differences i n the composition of feces as a r e s u l t of d i f f e r e n t d i e t s are c l e a r l y i n d i c a t e d and are consistant with the previous d i s c u s s i o n .


^3

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

FECAL OUTPUT

> π

>< > Ζ

Ο

70

Ζ OB 70 >

~Ό m η


.AMOUNT "> FED , FECAL 'OUTPUT

, AMOUNT H FED "TE—I χ 'I

AMOUNT FED

Ο FECAL

1 OUTPUT . AMOUNT ι FED FECAL OUTPUT

FECAL OUTPUT ON FIBER FREE DIET

« a e i a ÀHViaia ao saonnos ivNOiiNaANOONa


0.41

0.77

0.43

0.43

0.72

F i b e r Free

Pectin

Alphacel

Xylan

Corn bran

10.9

0.11

0.12

0.09

0.08

5.1 16.7

0.07 0.16

0.07 0.17

0.04 0.14

0.03 0.13

ARABINOSE Mean 95% C.I.

16.2

4.11

1.13

0.06

0.09

Mean

11.7 22.4

2.97 5.68

0.81 1.57

0.05 0.09

0.07 0.13

XYLOSE 95% C.I.

FECAL HYDROLYSIS RESULTS:

*For Grams Excreted/3 Day Pooled C o l l e c t i o n ; Ν = 5.

0.49 0.95

0.20 0.66

0.20 0.66

0.54 1.00

0.18 0.64

RHAMNOSE Mean 95% C.I

DIET

Table I I I .

0.15

0.32

0.61

0.13

0.07

0.10 0.23

0.21 0.49

0.40 0.92

0.08 0.19

0.05 0.11

MANNOSE Mean 95% C.I.

3.41

0.45

0.49

0.80

0.44

1.61 5.20

0.32 0.58

0.36 0.62

0.67 0.93

0.31 0.57

GALACTOSE Mean 95% C.I.

3.58

1.36

10.1

1.50

1.17

2.67 4.70

0.94 1.92

8.06 12.5

1.04 2.10

0.79 1.67

GLUCOSE Mean 95% C.I.

MEANS AND 95% CONFIDENCE INTERVALS*


238

UNCONVENTIONAL


Summary And

SOURCES

OF

DIETARY

FIBER

Conclusions

Marthinsen and Fleming (14) reported that methane e x c r e t i o n was g r e a t e r while consuming the xylan and p e c t i n d i e t s than while consuming the other d i e t s . Ingestion of these two f i b e r s a l s o caused higher f l a t u s volume and hydrogen and carbon dioxide exc r e t i o n . The A l p h a c e l and corn bran d i e t s r e s u l t e d i n breath and f l a t u s gas e x c r e t i o n at l e v e l s equivalent to the f i b e r - f r e e d i e t s . These observations are c o n s i s t e n t with the high recovery of f i b e r from the A l p h a c e l and corn bran and the i m p l i e d fermentation and hence low recovery of the x y l a n and the p e c t i n . The r e s u l t s from t h i s work show that d i e t a r y f i b e r sources produce d i f f e r e n t patterns of monosaccharides on d i r e c t TFA h y d r o l y s i s . The r e s u l t s a l s o show that i t i s p o s s i b l e to o b t a i n s i g n i f i c a n t information on the f a t e of d i e t a r y f i b e r sources by d i r e c t TFA h y d r o l y s i s of a l i q u o t s of recovered f e c a l m a t e r i a l . D i f f e r e n t d i e t a r y f i b e r sources give d i f f e r e n t amounts and patterns of monosaccharides that were r e l a t a b l e to the f i b e r sources ingested. A d d i t i o n a l experiments are needed to r e l a t e not only the monosaccharide composition of the f i b e r s fed to f e c a l output but a l s o the s t r u c t u r e s of those f i b e r s and how they may have been modified i n the d i g e s t i v e t r a c t even i f not fermented. The e f f e c t of f i b e r p a r t i c l e s i z e and pretreatment should be s t u d i e d . Free sugar, s t a r c h , c e l l u l o s e and u r o n i c a c i d measurements should be made i n order to o b t a i n a more complete p i c t u r e of what s u r v i v e s and what i s metabolized. The e f f e c t of d i e t a r y f i b e r s on the d i g e s t i o n and u t i l i z a t i o n of other polysaccharides and other food components should be s t u d i e d . This information, together with fermentation data, i n c l u d i n g gas and VFA production, w i l l provide a b e t t e r understanding of the r o l e and value of d i f f e r e n t d i e t a r y f i b e r s and t h e i r e f f e c t s on n u t r i e n t b i o a v a i l a b i l i t y . Acknowledgment The authors thank Dr. Bruce Mackey s t a t i s t i c a l p o r t i o n of t h i s work.

for his assistance for

the

Reference to a company and/or product named by the U. S. Department of A g r i c u l t u r e i s only f o r purposes of i n f o r m a t i o n and does not imply approval or recommendation of the product to the e x c l u s i o n of others which may a l s o be s u i t a b l e . Literature Cited 1. 2.

T r o w e l l , H. Lancet 1974, 1, 503. T r o w e l l , J . ; Southgate, D.A.T.; Wolever, T.M.S.; Leeds, A.R.L.; G a s s u l l , M.A.; Jenkins, D.A. Lancet 1974, 1, 967.


16.

3. 4. 5. 6.


7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21.

OLSON ET AL.

Cellulose, Xylan, Corn Bran, and Pectin

239

Southgate, D.A.T. "Current Developments of Importance to Health", Ed. Heaton, K.W. Food and Nutrition Press, 1979; Ρ 9. Cummings, J. H. Br. Med. Bull. 1981, 37, 65. Darvill, Α.; McNeil, M.; Albersheim, P.; Delmer, D.P. "Bio chemistry of Plants, Vol. 1 The Plant Cell", Ed. Tolbert, N.E., Academic Press, 1980; p 91. Aspinall, G.O. "Biochemistry of Plants, Vol. 3 Carbohydrate: Structure and Function", Ed. Tolbert, N.E., Academic Press, 1980; p 473. James, W.P.T.; Theander, O. Ed. "The Analysis of Dietary Fiber in Food", Marcel Dekker, Inc., New York, 1981. Theander, O.; Amin, P. "Dietary Fibers: Chemistry and Nu trition", Ed. Inglett, G.E.; Falkehag, S. I., Academic Press, 1979; p 215. Salyers, Α.; Palmer, J.K.; Balascio, J. ibid., p 193. Spiller, G.A.; Chernoff, M.C.; Hill, R.A.; Gates, J.E.; Nassar, J . J . ; Shipley, E.A. Am. J. Clin. Nutr. 1980, 33, 754. Ehle, F.R.; Robertson, J.B.; van Soest, P.J. J. Nutr. 1982, 112, 158. Calloway, D. "Handbook of Physiology Vol. 6", Ed. Code, C.F., Amer. Physiol. Soc., 1968; p 2839. Bond, J.H.; Levitt, M.D. Am. J. Clin. Nutr. 1978, 31, 169. Marthinsen, D.; Fleming, S.E. J. Nutr. 1982, 112, 1133. Albershiem, P.; Nevins, D.J.; English, P.D.; Karr, A.; Carb. Res. 1967, 5, 340. Olson, A.C.; Gray, G.M.; Chiu, M.C. 182nd meeting American Chemical Society, New York, 1981, AGFD No. 34. Prynne, C.J.; Southgate, D.A.T. Br. J. Nutr. 1979, 41, 495. Cummings, J.H.; Southgate, D.A.T.; Branch, W.J.; Wiggins, H.S.; Houston, H.; Jenkins, D.J.Α.; Jivraj, T.; Hill, M.J. ibid., p 477. Fengel, D.; Wegener, G. "Hydrolysis of Cellulose: Mecha nisms of Enzymatic and Acid Catalysis", Adv. in Chem. Series #181, Am. Chem. Soc., 1979; p 145. Heller, S.N.; Hackler, L.R.; Rivers, J.M.; van Soest, P.J.; Roe, D.A.; Lewis, B.A.; Robertson, J. Am. J. Clin. Nutr. 1980, 33, 1734. Dintzis, F.R.; Legg, L.M.; Deatherage, W.L.; Baker, F.L.; Inglett, G.E.; Jacob, R.A.; Reck, S.J.; Munoz, J.M.; Klevay, L.M.; Sandstead, H.H.; Shuey, W.C. Cereal Chem., 1979, 56, 123.

RECEIVED October 29, 1982


Unconventional Sources of Dietary Fiber - American Chemical Society

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