Evaluation of nutritional value and protein quality of raw and differentially processed sword bean [Canavalia gladiata (Jacq.) DC.] seeds.
Conventional legume seeds have been playing a key role as a source of protein in the diets of both human beings and animals, but their production is not sufficient to meet the increasing protein requirements, particularly in a developing country like India. To meet the inadequate supply of proteins in developing countries, where animal protein is grossly insufficient and also relatively expensive, recent research efforts are being geared towards finding out novel and economic sources of food proteins. Among the various alternative protein sources, the under-utilized legume seeds received more attention, whose protein potential remains under-developed. In this present study, the effect of various common processing methods on the nutritional value, antinutritional compounds, biological value and protein quality of seed materials of a South Indian under-utilized food legume, sword bean (SB) (Canavalia gladiata (Jacq.) DC.) was investigated. The mature raw SB seeds contained 28.39% of protein, 7.84% of lipid, 8.23% of fiber, 5.63% of ash and 49.91% of carbohydrates. The autoclaving treatment was more effective in reducing the maximum levels of various antinutritional compounds such as total free phenolics (91%), tannins (85%), L-Dopa (92%), phytic acid (83%), raffinose (84%), stachyose (66%), verbascose (83%), haemagglutinating activity (88%), trypsin inhibitor activity (75%) and á-amylase inhibitor activity (65%) without affecting the nutritional value of SB seeds when compared to soaking, cooking or roasting treatments. The rats fed with the experimental diet containing autoclaved SB seeds as a protein source exhibited better growth performance such as feed intake (219 g) and body weight gain (58 g). Moreover, the protein quality parameters such as true digestibility, biological value, net protein utilization and utilizable proteins were higher in the experimental diet containing autoclaved SB seeds as a protein ingredient. Hence, such autoclaving treatment could be recommended for the utilization of SB seeds as an alternative/additional protein source in the diets of human beings/animals.
Key words: Canavalia gladiata, sword bean, protein