Grape anthocyanin oligomerization: A putative mechanism for red color stabilization?

The equilibrium forms of malvidin-3-O-glucoside trimer were studied in aqueous solution at different pH values through UV-Visible spectroscopy. The reactivity of this compound is strongly dominated by acid-base chemistry, with the reaction sequence hydration-tautomerization-isomerization accounting less than 10% of the overall reactivity.