Complex enzyme hydrolysis of okara to enrich soluble dietary fiber and peptides and insights into the dietary fiber–protein interaction mechanism

The interaction between dietary fiber and protein inhibits the conversion of insoluble dietary fiber (IDF) into soluble dietary fiber (SDF) and the hydrolysis of okara protein. Viscozyme® L and pepsin were used for sequential enrichment SDF and peptides, and the interaction mechanisms between the fiber and protein were investigated by analyzing the structures of IDF, SDF, peptides, and their mixed systems. After complex enzyme hydrolysis, the SDF/IDF ratio and peptide content of okara reached 0.48 and 54.38%, respectively. Compared with hydrolysis using Viscozyme® L or pepsin alone, complex enzyme hydrolysis effectively degraded IDF and protein, disrupted hydrogen bonds in SDF–peptide, and hydrolyzed the amorphous regions of IDF. The hydrolysis of the amorphous regions of IDF and the disruption of hydrogen bonds between SDF and peptide enhanced the enrichment of SDF and peptides. Overall, this study provides a practical framework for the development and utilization of okara.