Solid-state fermentation of soybean okara: Isoflavones biotransformation, antioxidant activity and enhancement of nutritional quality

Okara Is a by-product of soybean processing produced in large quantities, but under-used by the food industry. Strategies to increase its nutritional quality could contribute to the usage of this biomass. Fresh and heat-treated okara were subjected to solid-state fermentation (SSF) using S. cerevisiae and physicochemical parameters of quality, total phenolics, beta-glucosidase activity, antioxidant activity and the biotransformation of isoflavone were evaluated. Fermentation contributed to the improvement of nutritional quality, promoting an increase in protein content, and increases in total phenolics, and antioxidant activity. SSF also promoted the bioconversion of isoflavone beta-D-glucosides to aglycone forms through the action of beta-glucosidases. Furthermore, SSF led to the reduction of raw fiber content with a potential improvement in digestibility. SSF was demonstrated to be a valuable tool in improving quality and functional attributes, and in adding value to okara, thus contributing to its better usage in the development of food products and supplements.