Effects of UV-A irradiation and microbial fermentation on the physicochemical, microstructure and functional properties of okara.

Whole utilization of okara has important economic value, but there are two technical barriers: coarse mouthfeel caused by insoluble dietary fiber (IDF) and undesirable "beany" off-odors. UV-A irradiation and/or microbial fermentation were used to modify okara. The results indicated that single and combined treatments increased the soluble dietary fiber (SDF) content. Saccharomyces cerevisiae fermentation (YUO), Lactiplantibacillus plantarum fermentation (LUO), and mixed fermentation (MUO) followed by UV-A irradiation of okara significantly reduced the IDF/SDF ratio to 2.48, 1.86 and 2.25, respectively. The modifications significantly reduced the lipid and total nitrogen contents and decreased the E-nose sensor values associated with beany odors. The combined treatment of microbial fermentation and UV-A irradiation partially destroyed the crystalline, resulting in a loose and porous surface, further enhanced the functional properties of water holding capacity, water solubility, antioxidant properties and cation exchange capacity. In particular, the DPPH and ABTS scavenging abilities of okara subject to microbial fermentation followed by UV-A irradiation were greater than that of other samples. These results indicate that the treatment sequence is very important for the functional properties of okara and microbial fermentation followed by UV-A irradiation is most conducive to improve the physicochemical properties and functionalities of okara.