The effect of preheated WPI interaction with AN on its complexes based on protein structure and function

This study investigated the structural and functional changes of the interaction between preheated whey protein isolate (WPI) and anthocyanin (AN) at different temperatures through Fourier transform infrared spectroscopy, endogenous fluorescence spectroscopy, and foaming properties. The results showed that preheat treatment reduced the average particle size of the solution and increased the absolute value of ζ-potential, and the whey protein isolate after heat treatment at 70 °C had the highest binding rate to anthocyanins, which increased from 87.44 to 89.67%. Preheat treatment significantly increased the surface hydrophobicity of WPI, but anthocyanins decreased the surface hydrophobicity of the composites. Fourier transform infrared spectroscopy results indicated that preheat treatment changed the secondary structure of the WPI and WPI-AN complexes, with the α-helix content decreasing and the β-fold content increasing. The endogenous fluorescence spectra analysis illustrated the preheating treatment exposed the internal chromogenic groups of the protein and that anthocyanins increased the polarity of the microenvironment of the protein fluorescent groups and changed the conformation. The foaming properties results revealed that the combination of AN improved the foamability and foam stability of WPI, and the foaming properties of the protein was significantly improved within a certain heat treatment temperature range. In this study, preheat treatment and complexation of anthocyanins were used to improve the structural and functional properties of whey isolate protein in expectation of improving the utilization value of WPI and to provide motivation and data reference for further application of WPI in food industry. Highlights 1. The preheated WPI contributes to the formation of WPI-AN composites. 2. The addition of anthocyanins led to changes in the structure and properties of preheated WPI. 3. The combination of AN improved the foamability and foam stability of WPI, and the foaming properties of the protein was significantly improved within a certain heat treatment temperature range.