Effect of transglutaminase on properties of tilapia scale gelatin films incorporated with soy protein isolate

The effect of transglutaminase (TGase) on the properties of tilapia scale gelatin films in the presence of soy protein isolate (SPI) was investigated. When 3% TGase was added into gelatin films, the total soluble matter and protein solubility of films were decreased from 89.36% and 92.78% to 35.83% and 40.05%, respectively, and the decline was promoted by adding 5% SPI. The strength of the films was increased by adding 1% TGase irrespective of SPI addition, but decreased when the TGase concentration was further raised. No obvious colour change was observed in the films with or without TGase and SPI. Based on the results of SDS–PAGE, DSC and SEM, it was revealed that the movement of low molecular weight hydrophilic protein was depressed by the cross-linking network structure induced by TGase and SPI during film drying, indicating that adding SPI is essential to improve the thermal stability and water resistance properties of TGase-induced gelatin films.