Interactions between anthocyanins and aroma substances in a model system. Effect on the flavor of grape-derived beverages

Evaluation of the sensory quality of wine or grape-derived beverages led us to study the interactions between flavors and anthocyanins, the colored family of polyphenols. The flavylium cation-ligand complexation, resulting in copigmentation (rise in pigment visible absorption with a concomitant bathochromic shift), was investigated using visible absorption spectroscopy. Sole volatile phenols were found to markedly interact with malvidin-3,5-O-diglucoside. With series of guaiacyl-derived aroma substances, acyl-substituted ligands proved to be better copigments than alkyl-substituted ones. Association constants and 1:1 complex stoichiometry were further determined for several substrates. Decreasing binding to malvin was observed for acetosyringone, syringaldehyde, acetovanillone, vanillin, 3,5-dimethoxyphenol, and 4-ethylguaiacol. Addition of 10% ethanol lowered by one-third the association constants for malvin-ligand couples and for malvidin-3-O-glucoside with acetosyringone and syringaldehyde. The main driving force was ascribed to hydrophobicity, although this study evidenced an influence of the ligand substitution pattern on copigmentation.