Effects of high-pressure treatment on some physicochemical and functional properties of soy protein isolates

The effects of high-pressure (HP) treatment on some physicochemical and functional properties of soy protein isolates (SPI) were investigated. Surface hydrophobicity (Ho), free sulfhydryl (SH) content, differential scanning calorimetry characteristics, protein solubility, emulsifying activities, and heat-induced gelling property were evaluated. HP treatment at 200–600 MPa resulted in a slight but gradual decline in solubility, and a significant (P<0.05) increase in Ho. Free SH content of SPI was significantly (P<0.05) increased after HP treatment at 200 MPa, but was gradually decreased with further increase in pressure. HP treatment at 200–600 MPa significantly (P<0.05) increased emulsification activity index, but decreased emulsion stability index. The heat-induced gelling property of SPI was also decreased by HP treatment. The influence of HP treatment on these properties was closely dependent on the protein concentration at which the SPI solutions were HP-treated. These results suggest that HP treatment could be used to modify the properties of soy proteins by appropriate selection of pressure level and protein concentration.