Fermentation of black soybean with Bacillus spp. for the production of kinema: changes in antioxidant potential on fermentation and gastrointestinal digestion.

Black soybean was fermented with four different potential Bacillus spp., including Bacillus licheniformis K1G, Bacillus subtilis K2B, Bacillus amyloliquefaciens K2G and Bacillus subtilis K2M, isolated from kinema, a traditionally fermented soybean product of Sikkim. Enhancement of antioxidant activity was observed with DPPH radical scavenging activity, reducing power potential and total antioxidant activity in methanolic as well as water extracts. Overall antioxidant activities were found to be higher in fermented black soybean in comparison to yellow soybean, showing its potential for production of kinema. Further, black soybean fermented using different starter was subjected to gastrointestinal digestion using pepsin and pancreatin. Upon gastrointestinal digestion of fermented black soybean changes in antioxidant activity was observed that was found to be reliant on the species and strains applied for fermentation as starter culture. Among different starters used for fermentation, black soybean fermented using B. subtilis K2M had higher DPPH radical scavenging and reducing power activity on gastrointestinal digestion. This study concludes that B. subtilis K2M can be applied for fermentation of black soybean for production of kinema as well as bioactive protein hydrolysates. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13197-021-05144-y. © Association of Food Scientists & Technologists (India) 2021.