Complexation of bovine β-lactoglobulin with malvidin-3-O-glucoside and its effect on the stability of grape skin anthocyanin extracts

The binding interaction between bovine beta-lactoglobulin and malvidin-3-O-glucoside (MG), the major anthocyanin in grape skin anthocyanin extracts (GSAE), was studied at pH 6.3 using fluorescence, Fourier transform infrared and circular dichroism spectroscopy. The binding constant (K-S), binding force and effect of the interaction on the beta-lactoglobulin conformation and GSAE stability were investigated. The results indicated that beta-lactoglobulin complexed with MG mainly via hydrophobic interaction with K-S of 0.67 x 10(3) M-1 at 297 K. The secondary structure of beta-lactoglobulin was changed by MG binding, with a decrease in a-helix, turn and random coil and an increase in beta-sheet. Bovine whey protein effectively prevented the color fading and degradation of anthocyanin in the GSAE solution during the thermal treatment (80 degrees C/2 h), H2O2 oxidation (0.005% H2O2/1 h) and photo illumination (5000 lx/5 d). The whey protein-anthocyanin complexation appeared to have a positive effect on the thermal, oxidation and photo stability of GSAE. (C) 2016 Elsevier Ltd. All rights reserved.