Cereal non-cellulosic polysaccharides: structure and function relationship - an overview

The non-cellulosic polysaccharides present in cereals (2-8%) are mostly arabinoxylans, (1 --> 3),(1 --> 4)-beta -glucans, pectins and arabinogalactans. Of these, the arabinoxylans are known to absorb large amounts of water and influence significantly the water balance, rheological properties of dough, and the retrogradation of starch and bread quality. (1 --> 3),(1 --> 4)-beta -glucans are known as biological response modifiers (BMS) as they are believed to modulate the immune response. Cereal Pectins and arabinogalactans form a very small amount and do not contribute substantially to the functionality of noncellulosic polysaccharides. Detailed structural investigations on cereal hetero xylans using modern techniques were initiated in the 1990s and still pose a challenge to carbohydrate chemists because of their structural complexity. Nutritionally, they are classified under "unavailable carbohydrates" (dietary fiber) along with lignin and cellulose and are known to have beneficial effects in alleviating disease symptoms such as diabetes, atherosclerosis, and colon cancer. In this review isolation, purification, characterization, structural elucidation, functional, and nutritional attributes of cereal heteroxylans are covered with particular emphasis on recently characterized finger millet arabinoxylans.