Effects of microbial fermentation and microwave treatment on the composition, structural characteristics, and functional properties of modified okara dietary fiber

Abstract The effects of mixed fermentation by lactic acid bacteria and Neurospora crassa, and microwave treatment on the composition, structure, and functional properties of okara DF were studied. The results of SEM and EDX showed that the honeycomb structure was more obvious and the content of elemental components was changed after fermentation and microwave treatment. The result of TGA-DSC showed that the thermal stability of the sample improved following microwave treatment. The FT-IR results showed that fermentation and microwave treatment have an effect on the functional groups of cellulose and hemicellulose consistent with the composition of the samples, and the crystal structure of samples was slightly damaged after modification. After mixed fermentation and microwave treatment, the adsorption effect of cholesterol and sodium cholate was not obviously changed. However, the α-Amylase activity inhibition ratio of fermented DF increased from 9.55% to 15.04% and 20.92% respectively. The glucose dialysis retardation of fermented DF doubled at 30 min. Overall, both methods improve the availability of DF in okara. Modified DF from soybean residue can be used as a functional ingredient in diverse food products.