Changes of Solubility and Rheological Property of the Isolated Soybean Protein after High Pressure Treatment and Its Mechanism

The changes as well as its mechanism of solubility and rheological property of the isolated soybean protein (ISP) in water solution after high pressure treatment were studied. The solubility of ISP was improved after high pressure treatment, which had the highest increment after pressurization at 400 MPa for 15 min, for the low concentration (4.0%～6.6%) of protein solution. The apparent viscosity of the ISP solution also increased after high pressure treatment. The storage modulus G' and the loss modulus G'' were increased as the treating pressure increasing. Results of the scanning electron microscope and polyacrylamide gel electrophoresis showed that the molecular of ISP in solution had some depolymerization and unfolding after the treatment at high pressures below 400 MPa. Meanwhile, the particles of the protein decreased and the fraction of protein particles in total volume increased. The infrared spectrum analysis of the pressurized ISP solution showed an increase of charge distribution of protein. It is suggested that the changes of physical and chemical properties of the pressurized ISP solution are due to the structural changes of ISP molecule.