Characterization and distribution of soluble and insoluble carbohydrates in lupin seeds.

White, blue and yellow lupin seeds were analyzed for their soluble and insoluble carbohydrate contents. The seeds contained only traces of starch. Their furfural generator contents were fairly constant (9.3--10.5%) and their soluble sugar contents were in the range of 11.8 to 14.1%. Thin-layer and column chromatography of the ethanol-soluble sugars showed the presence of varying amounts of ajugose, verbascose, stachyose, raffinose and sucrose. Quantitative analysis revealed an average of 25% sucrose in the total sugars, the major part of which is composed of alpha-galactosides. Separate analysis of the cotyledons (including the germ) showed that the latter contain 80% total carbohydrates, most of which were structural polysaccharides. The composition of the cell-wall constituents was examined after acid hydrolysis. Monosaccharides resulting after acid hydrolysis of the hemicelluloses were predominantly xylose and arabinose. Smaller quantities of galactose and glucose, and traces of rhamnose were also present. The cotyledons contain a considerable amount of soluble sugars (19.0%). Small amounts of glucose-containing polymers, soluble in water and dilute acid, were present in the cotyledons (1.0%); they increased to 2.4% in the hulls.