Interaction of mulberry anthocyanins with soybean protein isolate: effect on the stability of anthocyanins and protein in vitro digestion characteristics.

The interactions of anthocyanins and proteins might mutually influence each other on the physicochemical and functional properties. In this study, the interaction mechanism of soybean protein isolate (SPI) with mulberry anthocyanins (MA), and its effect on the thermal stability of anthocyanins and protein subunits' digestibility were investigated through multiple spectroscopies and in vitro gastrointestinal models. Results showed that cyanidin-3-O-glucoside (C3G), the main anthocyanin monomer in MA, could bind to SPI through hydrophobic interactions, resulting in static fluorescence quenching of SPI. The secondary structure of SPI changed by binding to C3G, with an increase of β-sheet and a decrease of α-helix and random coil. The formation of the SPI-MA complexes improved the thermal stability of MA at 353K, while, no significant protection occurred during heating at 368K. Complexation with MA promoted the digestibility of SPI by pepsin, especially the α′ and α subunits of β-conglycinin and the basic subunit...