Dietary fiber components

Molecular Interactions. Various polysaccharides readily associate with other substances, including bile acids and cholesterol, proteins, small organic molecules, inorganic salts, and ions. Anionic polysaccharides form salts and chelate complexes with cations some neutral polysaccharides form complexes with inorganic salts and some interactions are stmcture specific. Starch amylose and the linear branches of amylopectin form inclusion complexes with several classes of polar molecules, including fatty acids, glycerides, alcohols, esters, ketones, and iodine/iodide. The absorbed molecule occupies the cavity of the amylose helix, which has the capacity to expand somewhat to accommodate larger molecules. The starch—Hpid complex is important in food systems. Whether similar inclusion complexes can form with any of the dietary fiber components is not known. 

Little agreement has been reached as to which dietary components or which food processes physiologially affect mineral availability. Many plant foods contain phytic acid, oxalic acid or other dietary fiber components that can be shown to chelate minerals. The effect of these dietary substances upon the final bioavailability of the mineral in question will depend upon the digestibility of the chelate (106). 

R.G. Fulcher and S.S. Miller, Structure of Oat Bran and Distribution of Dietary Fiber Components. In P.J. Wood, (Ed.), Oat Bran, American Association of Cereal Chemists, St. Paul, MN (1993), ppl-24. 

K. M. Barford, R. A. McDonald, G. G. "Molecular Interactions of Dietary Fiber Components" presented at 179th ACS National Meeting, Houston, TX, 1980. 

Jeltema, M. A., Zabic, M. E., and Thiel, L. J. (1983). Prediction of cookie quality from dietary fiber components. Cereal Chem. 60 227-230. 

Theander, O. (1987). Chemistry of dietary fiber components. Scand. J. GasSroenSeroi., Suppl. 22(129), 21-28,... 

Shah, N., Atallah, M.T., Mahoney, R.R. and Pellett, P. 1982. Effect of dietary fiber components on fecal nitrogen excretion and protein utilization in growing rats, J. Nutr., 112 658-666. 

Because of the variety of polysaccharides which can be fermented by some Bacteroides species, it is difficult to predict with certainty which polysaccharides in the complex mixture of dietary and host-produced carbohydrates that enter the colon will be degraded most rapidly and most extensively. Further information about how these organisms make choices between different polysaccharides i vitro may help to clarify this issue. However, nutritionists who are interested in catabolism of dietary fiber components iji vivo should be aware that the bacteria may prefer other sources of carbohydrate, such as mucopolysaccharides from host secretions or even Maillard products, to the dietary polysaccharide under study, and that this preference may influence catabolism of a particular polysaccharide in ways which we cannot at present predict. Effects of this sort may be responsible for some of the individual-to-individual variation which is encountered in nutritional studies of dietary fiber utilization. 

Data have been presented emphasizing the variability of dietary fiber sources. Water holding capacity estimates differed by technique as well as source. The most Important advantage of the osmotic suction technique is that the measurement Includes the water soluble dietary fiber components. This is a more realistic model of the digestive tract. The human fecal batch in... 

The wheat bran is an attractive raw material for arabinoxylan production. The arabi-noxylan is the major dietary fiber component of wheat bran. Its extraction from the wheat bran by the ultrasound-assisted enzymatic treatment has been reported by Wang et al. The wheat bran is also an interesting source of glucose, xylose, and arabinose for bioconversion into ethanol. This low-cost residue is efficiently pretreated and hydrolyzed through the combination of nuld physicochemical methods and appropriated enzyme dosages. Thus, glucose to ethanol conversion of 95% was obtained by using Saccharomyces cerevisiae si. ... 

Yapo, B.M Koffi, K. L. Dietary fiber components in yellow passion fruit rind e a potential... 

Nystrom L., Lampi A.-M., Andersson AA.M., Kamal-Eldin A., Gebruers K., Courtin C.M., Delcour J. A., li L., Ward J.L., Fras A., Boros D., Rakszegi M., Bedo Z., Shewry P.R., Piironen V. Phytochemicals and dietary fiber components in rye varieties in the healthgrain diversity screen. Journal of Agricultural and Food Chemistry, 56 9758 9766 (2008). 

FIGURE 3.4 Chemical structure of the main insoluble and soluble dietary fiber components generally associated with cell walls, (a) Cellulose, (b) Hemicellulose. (c) Arabinoxylans. (d) p-Glucans. (e) Lignin. 

FIGURE 3.4 Chemical structure of the main insoluble and soluble dietary fiber components generally associated with cell walls.91... 

Dietary fiber is a mixture of simple and complex polysaccharides and lignin. In intact plant tissue these components are organized into a complex matrix, which is not completely understood. The physical and chemical interactions that sustain this matrix affect its physicochemical properties and probably its physiological effects. Several of the polysaccharides classified as soluble fiber are soluble only after they have been extracted under fairly rigorous conditions. 

Fiber components are the principal energy source for colonic bacteria with a further contribution from digestive tract mucosal polysaccharides. Rate of fermentation varies with the chemical nature of the fiber components. Short-chain fatty acids generated by bacterial action are partiaUy absorbed through the colon waU and provide a supplementary energy source to the host. Therefore, dietary fiber is partiaUy caloric. The short-chain fatty acids also promote reabsorption of sodium and water from the colon and stimulate colonic blood flow and pancreatic secretions. Butyrate has added health benefits. Butyric acid is the preferred energy source for the colonocytes and has been shown to promote normal colonic epitheUal ceU differentiation. Butyric acid may inhibit colonic polyps and tumors. The relationships of intestinal microflora to health and disease have been reviewed (10). 

Several physicochemical properties of dietary fiber contribute to its physiological role. Water-holding capacity, ion-exchange capacity, solution viscosity, density, and molecular kiteractions are characteristics determined by the chemical stmcture of the component polysaccharides, thek crystallinity, and surface area. 

However, fine grinding of iasoluble dietary fiber such as bran reduces WHC. In general, branched polysaccharides are more soluble than are linear polysaccharides because close packing of molecular chains is precluded. WHC is strongly kifluenced by the pentosan components of cell-waU dietary fiber and varies with the stmcture and source of these hemiceUuloses. 

Dietary fiber and fiber-rich food fractions bind bile acids and bile salts in vitro. This interaction is more pronounced for the lignin component. 

Table 8.4. Components of beverage dietary fiber (g/liter mean values SD n > 4)...

The mechanisms by which various forms of dietary fiber influence calcium bioavailability apparently also differ. In some cases, apparent dietary fiber effects on calcium bioavailability may be secondary to effects on bile acid and salt secretion and reabsorption or to other dietary components. 

In view of the practical importance of these grains, for example in dietary fibers, it is useful to study the cell wall polymers of their tissues during differentiation. In the present work, we used rice grains (brown rice without husk) as a starting material. They were fractionated into several distinct histological components, and the composition and detailed structure of cell wall polymers was compared. 

The bulk of potato tubers is made up of parenchyma cells that have thin, non-lignified, primary cell walls (Reeve et al., 1971 Bush et al, 1999, 2001 Parker et al., 2001). Unless stated to the contrary, potato cell walls refers to parenchyma cell walls. These walls and their component polysaccharides are important for a number of reasons they form part of the total intake of dietary fiber, influence the texture of cooked potato tubers and form much of the waste pulp that is produced in large amounts by the potato starch industry when starch is isolated. The pulp is usually used as cattle feed, but potentially could be processed in a variety of ways to increase its value (Mayer, 1998). For example, the whole cell-wall residues could be used as afood ingredient to alter food texture and to increase its dietary-fiber content, or cell-wall polysaccharides could be extracted and used in a similar way or for various industrial applications (Turquois et al., 1999 Dufresne et al, 2000 Harris and Smith, 2006 Kaack et al., 2006). 

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