Effect of processing on antinutrients and in vitro protein digestibility of the underutilized legume, Vigna unguiculata (L.) Walp subsp. unguiculata

The effects of hydration, cooking, autoclaving, germination and their combination on the reduction/elimination of antinutrients and the improvement of in vitro protein digestibility of the tribal pulse, Vigna unguiculata subsp. unguiculata were investigated. Hydration and germination processes were less effective in reducing l-Dopa and trypsin inhibitor activity. Cooking and autoclaving of presoaked seeds drastically reduced the content of total free phenolics, tannins, phytic acid, hydrogen cyanide, trypsin inhibitors and oligosaccharides. Germination (96 h) process reduced the total free phenolics, tannins, hydrogen cyanide and phytic acid. The combination of germination followed by autoclaving completely eliminated the total free phenolics, tannins, hydrogen cyanide, phytic acid, trypsin inhibitor, oligosaccharides and phytoheamagglutinating activity. The combination process (germination 96 h + autoclaving) improved the in vitro protein digestibility. We concluded that, a prolonged period of germination followed by autoclaving completely destroyed some of the antinutritional factors.

► Vigna unguiculata subsp. unguiculata is a valuable source of essential nutrients.
► Germination significantly reduced certain heat stable antinutritional factors such as phytic acid, tannins and oligosaccharides.
► Germination of presoaked seeds and autoclaving can be used to obtain enhanced protein quality of seed flour.