Effects of different tea polyphenols conjugated with β-lactoglobulin on antioxidant capacity and structural properties

In this study, we systematically compared the covalent effects of chlorogenic acid (CA), epigallocatechin gallate (EGCG) and gallic acid (GA) with β-lactoglobulin (βLG) under alkaline conditions. Based on the measurement of polyphenol binding equivalent, it was concluded that the binding ability of EGCG was strongest. Structural changes of βLG after covalent interaction with GA, CA and EGCG were investigated using fourier transform infrared spectroscopy, fluorescence spectroscopy analysis and dynamic light scattering, scanning electron microscopy. These results will help to elucidate the mechanism of covalent interaction of GA, CA and EGCG with βLG. Antioxidant activity test showed that polyphenols could significantly improve the antioxidant activity of βLG, indeed, βLG-EGCG had the strongest antioxidant properties. The DPPH radical scavenging ability of βLG-EGCG was increased by approximately 26%, and the ABTS radical scavenging ability of βLG-EGCG increased by 18%. These results may provide a theoretical foundation for the design functional products based on natural active ingredients.