Studies on carbohydrates of red gram (Cajanus cajan) in relation to milling

The nature of carbohydrates in a difficult‐milling and an easy‐milling cultivar of red gram (Cajanus cajan L) was studied. These two cultivars of red gram were milled to obtain cotyledon, intermediate fraction and husk, and various carbohydrate fractions were isolated from them and chemically characterised. The cotyledon was rich in starch and proteins and contained a water soluble polysaccharide mainly of arabinan type. The intermediate fraction had less starch than in the cotyledon and was rich in free sugars. Arabinogalactan‐type polysaccharides were characteristic of the intermediate fraction and were gummy and hygroscopic in nature. The alkali insoluble residue in the intermediate fraction was a complex of cellulose and non‐cellulosic polysaccharides. The content of this fraction and also of the pectin was greater in the difficult‐milling cultivar. The husk was rich in non‐starchy polysaccharides and contained varying amounts of arabinose and xylose in most of the fractions. Both glucuronic acid and galacturonic acid were present in the husk, whereas the cotyledon and intermediate fraction contained galacturonic acid only.