Effect of covalent modification by (-)-epigallocatechin-3-gallate on physicochemical and functional properties of whey protein isolate

The physicochemical and functional properties of covalently modified whey protein isolate (WPI) by (-)-epigallocatechin-3-gallate (EGCG) were investigated. WPI was chemically modified by EGCG under alkaline conditions. The effect of modification on foaming and emulsifying properties was evaluated. The results of SDS-PAGE and size exclusion chromatography indicated that modification by EGCG induced cross-linking on proteins of WPI. Fourier transform infrared spectroscopy (FT-IR) analysis illustrated the incorporation of phenolic groups into the modified WPI and the changes in protein secondary structure. Intrinsic fluorescence spectra revealed that modified WPI had a more compact tertiary structure compared to unmodified WPI. The modified WPI exhibited better foaming and emulsifying properties than unmodified WPI. These results suggest that EGCG modification is a potential method for improving the functional properties of WPI. (C) 2015 Elsevier Ltd. All rights reserved.