Effect of Ultrasonic Treatment Combined with pH Shift on Functional and Structural Properties of Potato Proteins and Correlation Analysis between Them

To enhance the functional properties of potato proteins (PP), this study investigated the effect of different ultrasonic treatments (at 0, 200, 300, 400, 500, and 600 W for 20 min) combined with pH shift on modifying the functional and structural properties of PP. Changes in the functional and structural properties of PP after modification were examined in terms of solubility, emulsifying and foaming properties, particle size, ζ-potential, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) patterns, Fourier transform infrared spectra (FTIR), fluorescence spectra, free sulfhydryl content, and surface hydrophobicity, and the correlation between functional and structural properties was analyzed. The results showed that the solubility of PP increased from 24.84% to 90.74% after pH shift to pH 12 in combination with 500 W ultrasonic treatment. Moreover, the emulsifying activity index (EAI) was enhanced by 86.37%, and the foaming capacity (FA) by 31.24%. Additionally, notable alterations in the molecular structure were observed accompanied by a decrease in the average particle size from 452.05 to 89.63 nm and a reduction in the ζ-potential value from −24.64 to −32.57 mV. The secondary structure analysis showed that the α-helix content decreased while the β-sheet content increased. The free sulfhydryl content and surface hydrophobicity significantly rose (P < 0.05). The results of correlation analysis showed that the solubility, emulsifying and foaming properties were negatively correlated with the particle size, turbidity and ζ-potential but positively correlated with the free sulfhydryl content and surface hydrophobicity. In conclusion, ultrasonic treatment combined with pH shift can improve the functional properties of PP, thereby expanding its score of application in the food industry.