ABSTRACT
Polysaccharides can be, and are, classified in several ways. Primarily because most food polysaccharides are polymolecular and, therefore, only statistical, rather than exact, structures can be written, and because even statistical structures are uncertain in some cases, classification by structure can be problematic. Polysaccharides that are basically insoluble at human-body temperature are classified as insoluble fiber; those that are basically soluble at human-body temperature constitute soluble fiber. Naturally occurring on food polysaccharides are ester groups, ether groups, and cyclic acetal groups. Carboxyl groups most often occur in food polysaccharides as part of the structure of a uronic acid unit. Polysaccharides can also be classified as to whether they are neutral, acidic, or basic, on the basis of three-dimensional structures, by solubility, and by general applications. Bacterial polysaccharides often contain regular repeating units, although postpolymerization modifications can result in variability in the repeating-unit structure.
