Chemical Composition and Biosynthesis of Dietary Fiber Components

Abstract

Plant cell walls are constituted by lignin and several homo- and heteropolysaccharides which include cellulose, hemicelluloses and pectins. Cellulose is a linear polymer constituted of D-glucopyranosyl residues joint by β-glycosidic bonds and constitutes the major building block of the wall structure. Soluble and insoluble hemicelluloses are classified into xylans, xyloglucan, arabynoxlans, mannans, glucomannans, and β-glucans. Pectins are covalently bound galacturonic acid-rich polysaccharides divided into galacturonans, or rhamnogalacturonan. Both types of pectins form gels and find widespread use in the food industry. β-glucans are inherent to cell walls of cereals, bacteria, algae and yeast and usually form a linear backbone primarily with 1–3 or 1–4 β-glycosidic linkages varying in molecular weight and branching. Fructans are polyfructosylfructose of four to several hundred residues that possess a sucrose core. Fructans are categorized into inulins, levans or phleins and gramminans. And lignin, considered as the second most abundant cell wall component, is synthesized to form the plant vascular system and to impart strength and structural support.