Preparation and characterization of whey protein isolate-dextran-proanthocyanidins ternary complexes: Formation mechanism, physicochemical stability

The present study aimed to improve the stability and antioxidant properties of whey protein isolate (WPI) in food emulsion systems. A whey protein isolate-dextran (D) binary complex (GF) was prepared using wet Melad reaction. Based on this, a ternary complex (GF-PC) system of whey protein isolate-dextran-proanthocyanidins (PC) was constructed. The interaction mechanism and functional properties of this ternary system were investigated by turbidity, Fourier infrared, and fluorescence spectroscopy, as well as DPPH radical scavenging ability. Results showed that a novel ternary composite system was successfully constructed. The maximum encapsulation efficiency of PC was 93.09% when using the GF-0.4 PC complex (the mass ratio of GF to PC was 1:0.4). Turbidity, fluorescence spectroscopy, and FTIR spectroscopy analyses showed that PC was successfully encapsulated by GF and formed the ternary complex. SDS-PAGE and interaction forces showed that the noncovalent contacts increased significantly, while covalent interactions remained the main interaction between WPI, D, and PC. The GF-PC ternary complexes significantly improved emulsification properties and free radical scavenging ability compared to single WPI and GF conjugates. This study suggested that GF-PC could be used as a delivery system for functional active ingredients with enhanced emulsifying activity and antioxidant capacity.