Effects of Xanthan Gum on Rheological Properties and Microstructure of Soy Protein Isolate Gel

Xanthan gum (XG) and soybean protein isolate (SPI) were used as raw materials to prepare XG-SPI mixed gel by ultrasonic pretreatment and glucolactone induction. Rheological tests and scanning electron microscopy were used to study the effects of different concentrations of XG on viscoelasticity, self-healing ability, thermal stability and microstructure of SPI gel. Results showed that SPI gel was a typical viscoelastic material with strong frequency dependence. With the increasing of XG concentration (1%~5%), the elastic modulus and viscous modulus of the mixed gel increased, and the loss tangent decreased, and the gel strength increased. The addition of XG affected the self-healing ability of SPI gel, although the healing time was prolonged, the recovery rate increased. The SPI single gel which was heated (25~100 ℃) occurred a transition of gel-sol state and it structure was extremely damaged. Comparatively, the thermal stability of XG-SPI mix gel increased significantly. The microstructural changes of SPI single gel and XG-SPI mixed gel were not observed under electron microscope. The results of this study could provide important information for developing new soy protein isolate gels with improved quality.