Polysaccharide other than starch, cereal

Cereals also contain polysaccharides other than starch. In endosperm cells their content is much less than that of starch (cf. Table 15.29). They include pentosans, cellulose, 3-glucans and glu-cofructans. These polysaccharides are primarily constituents of cell walls, and are more abundant in the outer portions than the inner portions of the kernel. Therefore, their content in flour increases as the degree of fineness increases (cf. rye as an example in Table 15.36). 

From a nutritional and physiological viewpoint, soluble and insoluble polysaccharides other than starch and lignin (cf. 18.1.2.5.1) are also called dietary fiber. The most important fiber sources are cereals and legumes, while their content in fmits and vegetables is relatively low. 

There has been much debate of the definition of dietary fiber and in particular whether it should include carbohydrates other than nonstarch polysaccharides. Recently, the American Association of Cereal Chemists (AACC) proposed a new definition of dietary fiber, which would include both oligosaccharides and resistant starch as well as associated plant substances. This new definition would also require complete or partial fermentation and demonstration of physiological effects such as laxation, and reduction in blood glucose or blood cholesterol. A similar approach to include beneficial physiological effects is also proposed by the Food and Nutrition Board of the US Institute of Medicine. 

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