Soy protein isolate with higher solubility and improved gel properties when co-assembled with walnut protein

Phytoproteins have been widely implemented in the food industry benefiting from their good functionalities, vast reserves and relatively low cost. However, phytoproteins frequently experience poor solubility, which limits their applications. In our study, the solubility of soy protein isolate (SPI) treated with pH-shifting increased over 1.8 times; however, the transglutaminase-induced gel properties were sacrificed. To solve this problem, walnut protein (WP) was used to co-assemble with SPI during the treatment. The co-assembly hybrid protein shows significantly better solubility, meanwhile, maintaining the transglutaminase-induced gel properties and improving the cohesiveness and resilience properties compared with untreated SPI, which behaved an improved water holding capacity during storage. The detailed mechanisms were investigated with rheological analysis, SEM, textural analysis and Fourier transform infrared spectroscopy (FTIR). Overall, our study provided a promising strategy to develop SPI/WP hybrid composites with high solubility and improved gel properties to extend the application of SPI in the food industry. The pH-shifting treatment of co-assembly hybrid SPI and WP not only enhanced the solubility of SPI and solved the dilemma of its low solubility, but also improved the gel properties of SPI, which led to a wider range of applications in gel compounded food products. image