Effects of high hydrostatic pressure on the functional properties of soy protein isolate

In this study, functional properties of high hydrostatic pressure (HHP)-treated soy protein isolate (SPI) samples including protein solubility, emulsification activity (EA), and water holding capacity (WHC) were studied. Fourier transform infrared spectroscopy (FTIR), viscosity, and nuclear magnetic resonance (NMR) relaxometry experiments were performed. Three pressure (300, 400, and 500 MPa), two pH (5.0 and 7.0), and two temperature levels (25 and 40(degrees)C) were used to prepare SPI samples. Solubility of SPI was more pH-dependent than HHP-dependent, whereas WHC was more sensitive to pressure. Samples processed at 300 MPa, pH 5.0, and 40(degrees)C demonstrated higher EA (p < .05) than the untreated samples. Pressure application significantly reduced the viscosity of SPI dispersions (p < .05). Samples processed at 300 MPa, pH 5.0, and 40(degrees)C and at 400 MPa, pH 5.0, and 40(degrees)C attained the longest transverse relaxation time (T2) values reflecting their low solubility profiles. Thus, results indicated that HHP was able to modify the functional properties of SPI at different temperature and pH conditions.