Improving the Solubility of Soybean Protein Isolate by High-Intensity Ultrasound
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Abstract:
In this study, the effect of high-intensity ultrasonic treatment on the solubility of the 3% (W/V) and 5% (W/V) commercial soy protein isolate (SPI) was investigated. The effects of high-intensity ultrasonic treatment on the surface hydrophobicity, particle size and electrophoretic mobility of SPI were examined to analyze the mechanism underlying the influence of SPI’s structural changes on its solubility. Results showed that the high-intensity ultrasonic treatment (200~800 W) could improve significantly the solubilities of the commercial SPI products at two mass concentrations. With the increase in ultrasonic power, SPI solubility increased first and then decreased. The ultrasonic treatment at 400 W could lead to the maximum solubility (47.86%), which increased by 87.4% compared to the control. After each of the ultrasonic treatments (except for that at 800 W), the solubility of 3% (W/V) SPI was higher than that of 5% (W/V) SPI. The results of surface hydrophobicity and particle size showed that the low-power ultrasonic treatment could induce partial depolymerization of SPI aggregates, reduce protein’s surface hydrophobicity and particle size thereby increasing solubility of SPI. However, high-power ultrasonic treatment could induce the re-formation of insoluble aggregates, leading to the decrease of SPI solubility. Results of SDS-PAGE showed that the ultrasonic treatment did not destroy the structure of protein subunits. The results showed the optimal improvement of the solubility of the 3% (W/V) SPI obtained by the ultrasonic treatment at 400 W. This work provides guidance for improving the solubility of commercial SPI.
