Incorporation of High-Speed Shearing in the Fabrication of Whole Soybean Curd: Effects on Aggregation Behaviors and Microstructures

High-speed shearing (HSS) technology was used to mill the okara fibers in raw whole soybean flour (rWSF) suspension for fabrication of whole soybean curd (WSC). By measuring the medium diameter and analyzing the protein subunit composition of rWSF and heated whole soybean flour (hWSF), we found that HSS effectively micronized the insoluble fraction in suspension (especially the component cell layers of seed coat) but destroyed the structure of the native protein and caused the disappearance of specific protein band 7 in sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Further, we made WSC using HSS-treated hWSF suspension and analyzed its characteristics. The relative contents of α-helix, β-sheet, and β-turns all decreased after HSS, but the surface hydrophobicity showed an opposite trend. Additionally, the maximum emission wavelength blue- shifted after HSS. These results indicated that the secondary and tertiary structures of WSC were changed by HSS. Moreover, microstructural analysis based on a field emission scanning electron microscope (FESEM) and texture analyzer suggested that HSS led to the formation of a loose and less connected gel network and weakened the gel strength consequently. In summary, to separate and micronize okara individually and add them back to soymilk for WSC making was a considerable method.