Combination of pulsed electric field and pH shifting improves the solubility, emulsifying, foaming of commercial soy protein isolate

In this study, the effects of a new dual modification method, pulsed electric field (PEF) and pH shifting treatment, on the solubility, emulsifying and foaming properties of commercial soy protein isolate (SPI) were investigated. Results showed that the combination of PEF and pH shifting treatment, particularly at moderate PEF strength (10 kV/cm) and alkaline conditions (pH 11), facilitated protein structure unfolding and formation of smaller aggregates, substantially enhancing the solubility of SPI from 26.06% to 70.34%. Higher flexibility, surface hydrophobicity, and free sulfhydryl content were also found in the modified SPI, which boosted interfacial activity and significantly enhanced emulsifying and foaming properties. In alkaline environments, the enhanced functional properties of SPI at moderate PEF strength may be attributed to the appropriate oxidation of proteins by free radicals produced by electrochemical processes and the additional unfolding of protein conformations by polarization. The functional characteristics of SPI were decreased by an increase in PEF strength (20 kV/cm), which may be due to the tendency of the protein to aggregate and undergo excessive oxidation. This work may provide an effective methodological and theoretical basis for the modification of SPI by combining PEF and pH shifting treatment.