Study on effect of papin hydrolysis and TGase cross-linking on emulsifying properties of soy protein isolate

The effect of papain hydrolysis and TGase cross-linking on emulsifying properties of soy protein isolate (SPI) was investigated. The effect of the cross-linking with samples on different degrees of hydrolysis on the particle size distribution, the mean diameter per particle surface area and the centrifugal creaming rate of the emulsions were analyzed. The effect of different store conditions, such as room temperature storage, cold storage and freeze storage, on the flocculation stability and coalescence stability of samples were also studied. The result showed that:in the range of degree of hydrolysis (DH 2%¹0%) , the emulsifying activity of papain hydrolyzed SPI improved with the increase of DH. TGase cross-linking improved the emulsifying stability effectively, especially the cross-linked hydrolyzed SPI with lower DH. The optimum emulsifying stability was obtained when cross-linked the hydrolyzed SPI in DH 10%. During room temperature, the flocculation stability could improve effectively by TGase cross-linking of papain hydrolyzed SPI (DH 6%¹0%) . Freeze-thaw process would decrease the coalescence stability of emulsion stabilized with SPI, and the emulsions stabilized with cross-linking of the hydrolyzed SPI (DH 6%¹0%) could improve the coalescence stability. Thus, these modified samples could be used in some frozen food.