Effects of Rice, soy, and whey protein additions on quality characteristics and in vitro digestibility of Rice cakes

Current studies on in vitro starch digestion have focused on naturally occurring starch-protein interactions in plant seeds, whereas the effect of exogenous protein-starch interactions as well as the effect of adding endogenous proteins on starch-protein interactions remains unclear. In this study, rice cake was employed as a case study to investigate the effects of rice protein (RP), soy protein isolate (SPI), and whey protein isolate (WPI) at varying concentrations on physicochemical properties and in vitro digestibility. RP decreased water absorption, while SPI and WPI increased it. RP and WPI significantly increased the double-helical content of starch molecules in rice cakes, whereas SPI showed no significant effect on the DD values. Protein addition enhances the thermal stability of rice cakes. Notably, the digestion data demonstrated that protein addition enhanced rice cake digestibility. Meanwhile, starch composition analysis revealed that protein addition had less impact on rapidly digestible starch (RDS), it increased the content of slowly digestible starch (SDS) but decreased resistant starch (RS).