Effect of High Intensity Ultrasound on the Conformational and Physicochemical Properties of Soy 7S and 11S Globulin

The effects of high intensity ultrasound treatment (150, 450, 1350 W) on the conformational and physicochemical properties of soy 7S and 11S globulin for different durations (15, 30 min) were investigated. The results showed that ultrasound treatment did not change the primary structures of 7S and 11S, but were able to change the content of the components in the secondary structure. Ultrasound treatment resulted varying degrees of reduction in fluorescence intensity and a significant increase (P<0.05) in surface hydrophobicity (H₀) for 7S and 11S. Particle size distribution measurements showed that the droplets of 7S and 11S were more uniformly distributed after ultrasound treatment and that the stability of the protein solutions was improved. Differential scanning calorimetry (DSC) results showed that the enthalpy (ΔH) decreased from 1.22 J/g to 0.17 J/g for 7S and from 1.41 J/g to 0.53 J/g for 11S after sonication, requiring less energy to unfold the protein structure. In terms of physicochemical properties, the emulsification activity and emulsion stability of 7S and 11S increased significantly (P<0.05) after sonication, and the solubility increased by up to 12.85% and 10.57%, respectively. In addition, cryo-scanning electron microscopy (Cryo-SEM) observations revealed that the microstructure of 7S and 11S changed after sonication from a more ordered reticular aggregated state to a disordered state. Thus, high intensity ultrasound treatment can obviously affect the structure and physicochemical properties of 7S and 11S.