Polysaccharides dietary fiber

CUMMINGS J H (1992) Fecal weight, colon cancer and dietary fiber intake of non-starchy polysaccharide(dietary fiber). Gastroenterology, 103 1783-9. 

Tungland, B.C. and Meyer, D., Nondigestible ofigo- and polysaccharides (dietary fiber) Their physiology and role in human health and food, CompreherL Rev. Food ScL Food Safety, 1, 73, 2002. 

Englyst, H.N. and Cummings, J.H., Non-starch polysaccharides (dietary fiber) and resistant starch. New Developments in Dietary Fiber, Furda, I. and Brine, J. (Eds.), Plenum Press, New York, p. 205, 1990. 

Historically, dietary fiber referred to iasoluble plant cell wall material, primarily polysaccharides, not digested by the endogenous enzymes of the human digestive tract. This definition has been extended to iaclude other nondigestible polysaccharides, from plants and other sources, that are iacorporated iato processed foods. Cellulose [9004-34-6] (qv) is fibrous however, lignin [9005-53-2] (qv) and many other polysaccharides ia food do not have fiberlike stmctures (see also Carbohydrates). 

The variation ia water solubiUty among polysaccharides results ia varied physiological roles. Plant ceU-waH polysaccharides and lignin provide iasoluble dietary fiber (IDF) nondigestible storage polysaccharides, some pectic polysaccharides, and most of the functional additives contribute soluble dietary fiber (SDF). 

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. 

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. 

SRB contains high-quality protein, oil, dietary fiber, polysaccharides, fat-soluble phytochemicals (plant derived bioactive compounds) and other bran nutrients. Rice bran and germ are the richest natural sources of B complex vitamins as well as E vitamins, polyphenols, several antioxidants and minerals. It is now available in the commercial food ingredient market as a safe and effective functional food and dietary supplement. 

Englyst HN and Cummings JH. 1988. Improved method for measurement of dietary fiber as non-starch polysaccharides in plant foods. JAOAC 71 808-814. 

Several other properties of selected dietary fibers may influence the bioavailability of calcium directly or indirectly. Those fibers which have cation exchange capabilities such as acid polysaccharides due to free carboxyl groups on the sugar residues may bind minerals such as calcium (3,17,33,36). Loss of calcium binding protein as a result of mucosa injury caused by the feeding of some kinds of dietary fiber was credited as being the partial cause of decreased calcium absorption in everted, rat gut sac studies by Oku et al. (16). 

Van Soest, P.J., Robertson, J.B. and Lewis, B.A. (1991) Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition. Journal of Dairy Science 74, 3583-3597. 

Carcinogenesis inhibition. Polysaccharide fraction of the dried seed hulls, administered to rats by gastric intubation, was active vs tumor induction with N-ethyl N-nitro-N nitrosoguanidine h Rice bran, administered orally to male rats at a concentration of 4% of the diet, was active. A 1 1 combination of wheat bran and psyllium, at a total level of 8% dietary fiber, offers the highest protection against colon tumor development . 

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). 

In addition to the walls of the parenchyma cells, the walls of the periderm (skin) cork cells form part of the total intake of dietary fiber and a waste product of potato processing for food as well as for starch. Although much is known about the suberin present in these cell walls (Bernards, 2002 Franke and Schreiber, 2007 Grafos and Santos, 2007), little is known about their polysaccharides (Harris et al., 1991). Nonetheless, because of the presence of suberin, these cell walls are able to adsorb hydrophobic dietary carcinogens and their intake may be important in the prevention of colorectal cancer (Harris et al., 1991 Ferguson and Harris, 1998, 2001). 

Definition Mainly cell wall polysaccharides and the principal component of dietary fiber. 

Relevance to potatoes Dietary fiber includes cell wall NSP and RS, as both are digestion-resistant polysaccharides and both enter the colon where they may contribute to colonic health. NSP is low in potatoes but with RS formation NSP + RS (= dietary fiber) in potatoes can reach levels that allow the nutrient claim high in dietary fiber. ... 

Sea animals are rich in soluble dietary fibers, proteins, minerals, vitamins, antioxidants, phytochemicals, and polyunsaturated fatty acids, with low caloric value. Polysaccharides from marine animals have been reported to possess biological activities with potential medicinal values in addition to their current status as a source of dietary fibers and prebiotics. Moreover, they have a lot of dietary fiber, which lowers blood cholesterol, and iodine, which improves metabolism, vascular and cardiac action, body temperature, and perspiration regulation, and are effective in... 

The exoskeletons (protective shells) of insects and some marine organisms, such as crabs and shrimp, are made of chitin, a hard, resilient polysaccharide made of the monosaccharide A acetylglucosamine, as shown in Figure 13.5b. Wood varnish once contained chitin from the exoskeletons of insects. In powdered form, chitin is now finding use as a dietary fiber supplement. 

Carbohydrates generally supply about 45% of our energy requirement. Dietary carbohydrates include monosaccharides (such as glucose and fructose), disaccharides (such as sucrose and lactose), and the longermonosaccharide units arc classed as oligosaccharides.) Dietary polysaccharides include starches, such as amyJose and amylopectin, and some of the dietary fibers. 

FIGURE 3.4 Structures of the dietary fibers pectin and cellulose Also shown ate the sugars that make up the polysaccharide backbone and side chairs of the heterogereoiis compound hemicelluiose... 

Polyps, 882-884, 886 PolysacchaHdaS, 10,12 dietary fibers, 140-147 rumstEuch polysaccharides, 141 Polyunsaturated fatty acids (PtJi- As), 361, 364,366... 

---