Covalent complexation and functional evaluation of (-)-epigallocatechin gallate and α-lactalbumin

The covalent complexation between (-)-epigallocatechin gallate (EGCG) and a-lactalbumin (alpha-La), and the effect of EGCG on the antioxidative activity and emulsifying properties of alpha-La were investigated. The turbidity of a solution of 1% alpha-La and 0.2% EGCG decreased after 24 h reaction at pH 8.0 and 60 degrees C, less than the value of C alpha-La alone. The interaction between alpha-La and EGCG at pH 8.0 was more pronounced than that at pH 6.0 or 7.0, as evidenced by the reduced amplitude of amide A, and I, and II bands of alpha-La by FT-IR and the increase in the total phenolic content and denaturation temperature. These results implied that EGCG was covalently linked to alpha-La at pH 8.0. In addition, compared with the control of alpha-La, alpha-La-EGCG complexes had significantly increased antioxidative activity. The emulsions stabilized by alpha-La-EGCG complexes, compared with that by alpha-La alone, had much smaller droplet sizes, which indicated the emulsifying property of alpha-La was improved. (C) 2013 Elsevier Ltd. All rights reserved.