Functional properties and sensitization of β-lactoglobulin were improved by covalent binding with exopolysaccharides and (−)-epigallocatechin gallate

Β-lactoglobulin (β-LG) was a major allergen in cow's milk and its sensitization has severely limited the dairy consumption. In this study, a ternary complex was prepared by covalent binding β-LG to exopolysaccharides (EPS) derived from Lactiplantibacillus plantarum A81 and (−)-epigallocatechin gallate (EGCG), i.e. β-LG-EPS-EGCG. In order to minimize protein oxidation and prevented polyphenol aggregation, the EPS-EGCG complex was firstly synthesized by a free radical method, followed by covalent binding to β-LG via Maillard reaction. The structural features of β-LG-EPS-EGCG were analyzed using SDS-PAGE, FT-IR, UV and fluorescence spectroscopy, SEM and DSC. The results indicated that the secondary structure of ternary complex was obviously altered in comparison with that of native β-LG, accompanied by decreased α-helix content (from 20.19 % to 11.33 %), increased random coil and β-sheet contents (from 20.09 % to 24.16 % and from 29.90 % to 32.21 %, respectively). Meanwhile, the intrinsic fluorescence was quenched in β-LG-EPS-EGCG complex, thermal stability and emulsibility were significantly enhanced. Additionally, the β-LG-EPS-EGCG complex showed enhanced antioxidant activity. Notably, β-LG specific IgE binding capacity was significantly reduced for β-LG-EPS-EGCG complex compared to that of native β-LG, implying a decreased allergenicity. This study confirms that the binding among polyphenols, proteins and EPS can effectively reduce the sensitization of β-LG and enhance its functional properties, which provides a new idea for the development of hypoallergenic dairy products