Surface properties and structure characteristics of soybean protein isolate by limited hydrolysis

The surface adsorption properties of soy protein isolated (SPI) were obviously improved after limited hydrolysis by trypsin. When the hydrolyzing degree (DH) of SPI was controlled from 2% to 6%, the surface tension behavior of modified SPI was decreased with the hydrolyzing degree increasing. Compared to the natural soy protein, the values of surface tension of modified SPI which DH was 4% decreased by 19.35% and the foamability increased by 22.03%. The variations of surface properties of modified SPI were related to its structural change, it presented better surface hydrophobic properties, lower electric surface charge, and the increased viscosity which was apt to adsorb at interface of two phase region as compared to the natural soy protein which had poor behaviors of foams and emulsions.