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 β-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 (KS), binding force and effect of the interaction on the β-lactoglobulin conformation and GSAE stability were investigated. The results indicated that β-lactoglobulin complexed with MG mainly via hydrophobic interaction with KS of 0.67×10(3)M(-)(1) at 297K. The secondary structure of β-lactoglobulin was changed by MG binding, with a decrease in α-helix, turn and random coil and an increase in β-sheet. Bovine whey protein effectively prevented the color fading and degradation of anthocyanin in the GSAE solution during the thermal treatment (80°C/2h), H2O2 oxidation (0.005% H2O2/1h) and photo illumination (5000lx/5d). The whey protein-anthocyanin complexation appeared to have a positive effect on the thermal, oxidation and photo stability of GSAE.