Species/variety differences in biochemical composition and nutritional value of Indian tribal legumes of the genus Canavalia.

Seeds of the Indian tribal pulses Canavalia gladiata (red and brown varieties), C. ensiformis and C. virosa were analysed for their physical characters, proximate composition, minerals, amino acid composition, dietary fibre constituents, starch fractions, fatty acid profiles and various antinutritional and/or toxic factors. Among the different species/varieties of Canavalia, the brown variety of C. gladiata was found to have the highest amount of protein (35.0%). The essential amino acid profile of total seed proteins compared favourably with the FAO/WHO reference pattern established for pre-school children, except for a deficiency of sulphur containing amino acids in both varieties of C. gladiata and C. ensiformis, whereas high concentrations of cystine and methionine were detected in C. virosa. However, tryptophan in the red variety and lysine in the brown variety of C. gladiata seemed to be the second most limiting amino acids. Generally, these Canavalia seeds appear to be a good source of potassium, phosphorus and calcium. They contain low levels of sodium. Even though the samples contained a high proportion of total starch (31.8-36.9%), the percentage of digestible starch appeared to be much higher in C. ensiformis (70.6%) and C. virosa (71.8%) than in C. gladiata. The seed lipids of all the Canavalia samples investigated had a large proportion of unsaturated fatty acids (71-78%) with oleic acid as the major one (38.6-47.4%). All samples were rich in dietary fibre (17.5-23.6%), most of which was insoluble dietary fibre. The level of the toxic amino acid, canavanine, was found to be relatively low (27-42%) in C. gladiata and C. ensiformis compared to previous literature reports for the same species. The other antinutrients such as phenolics, tannins, condensed tannins, saponins, protease inhibitors, alpha-amylase inhibitor and haemagglutinating activity were also analysed and reported here. C. ensiformis seeds exhibited a relatively high level (69.0%) of in vitro protein digestibility compared to the red (67.2%) and brown (65.4%) varieties of C. gladiata and C. virosa (62.5%).