Improvement of CaSO₄-Induced Gelation Properties of Soybean Protein Isolate by Pre-crosslinking with Transglutaminase

Enzymatic modification can effectively improve the gel property of soybean protein. In order to study the effect of transglutaminase (TGase) pre-crosslinking on the properties of salt induced soy protein isolate (SPI) gel, SPI dispersions with different crosslinking degree were prepared by controlling the enzyme concentration and the pre-crosslinking time, and their gelation properties under the action of CaSO₄ were studied. The results showed that compared with SPI without TGase treatment, appropriate pre-crosslinking of protein could significantly improve the quality of SPI gels. After 3~5 U/g TGase crosslinking for 20 min or 3 U/g TGase crosslinking for 20~30 min, the properties of SPI gel were improved to different degrees, among which the elastic modulus, yield stress, yield strain and water holding capacity were increased by 124.6%, 269.0%, 135.0% and 53.0%, respectively. However, excessive crosslinking produced protein aggregates with too large size, resulting in coarse and porous gel structure and significantly decreased (P<0.05) in gel strength and water holding capacity. It can be seen that proper utilization of TGase can improve the quality of SPI gel products, which has important guiding significance for the application of TGase in food industry and the improvement of texture of traditional soybean products.