Ultrasound-high pressure combined treatment effects on structure and physicochemical properties of soybean protein isolate

Effects of combined ultrasound and high-pressure treatment on the structure and physicochemical properties of soybean protein isolate (SPI) were explored using infrared and fluorescence spectroscopy, an assay kit, and texture profile analysis. The combined treatment of ultrasound and high pressure resulted in the transformation of the secondary structure from order to disorder and a looser tertiary conformation. The ultrasound, followed by high-pressure treatment, resulted in a more significant unfolding of SPI structure, and further increased the thermal stability and surface charges, while reducing the average particle size. The surface hydrophobicity, free sulfhydryl groups, and solubility of SPI treated with 480 W ultrasound followed by high pressure were enhanced by 1.98 times, 47.74% and 1.42 times, respectively. Meanwhile, both emulsification and gelation properties reached the optimal levels. Modified SPI can be used as a processing raw material to apply in the design and development of high-stability emulsions or high-strength gels.