Soybean okara: Effect of ultrasound on compositional and emulsifying properties

Abstract

High-intensity ultrasound is widely used to modify the functional properties of macromolecules (proteins, polysaccharides, etc.) and to expand their range of potential applications. This work is aimed at studying the effects of ultrasound treatments on the composition of different soybean okara samples and their potential as an emulsifying agent. Defatted solvent-free soybean flour (DSF) was extracted by adjusting dispersion to pH 9.0. Insoluble residues obtained after centrifugation were dried, and an unsonicated okara sample (UOK) was obtained. Furthermore, the soybean flour dispersion was subjected to treatment in a probe-type ultrasonic homogeniser before or after the alkaline extraction process, thus producing SOK and OKS samples, respectively. The sonication process generated compositional and structural changes in okara soybeans. SOK had higher yield and protein content than UOK and OKS due to the insolubilisation of the glycinin (11S) fraction of soybean storage proteins. Due to these characteristics, the SOK sample showed the best emulsifying activity.