Chemical composition of three underutilized legume seeds grown in China

Abstract

Proteins of Phaseolus angularis, Phaseolus calcaratus and Dolichos lablab seeds (24.9 to 26.5% dry weight) were mainly contributed by their cotyledons which had a proportion of 82.9 to 90.8% by weight of the whole seeds. The levels of all the essential amino acids of the legume seeds (415 to 443 mg g −1 protein) were above the FAO/WHO, (1990) requirement with the essential amino acid scores of the methionine and cystine being 1.02 to 1.19. Appreciable amounts of oligosaccharides of the raffinose family were found mainly in the cotyledons (3.52 to 4.72% dry weight). The total dietary fibre of the legume seeds (13.5 to 19.3% dry weight) consisted predominantly of insoluble dietary fibre (IDF). The cotyledons contained 45.9 to 51.4% dry weight of starch but had low contents of cellulose and lignin. Hulls were highly lignified and consisted predominantly of IDF, with values ranging from 70.7 to 74.0% dry weight. The principal sugar residue analysis revealed that pectins were the major polysaccharide present in the SDF of both the cotyledons and the hulls. While xylans and cellulose were the major polysaccharides present in the IDF of the hulls, xyloglucans and arabinose-rich pectic substances were the principal non-starch polysaccharides in the IDF of the cotyledons.