Influence of structure on colour stability of anthocyanins and flavylium salts with ascorbic acid

Ascorbic acid (330 mg/l) was added to buffered solutions (pH 2.35) of malvidin 3-glucoside, malvidin 3,5-diglucoside and flavylium salts with differing 4-substituents, viz.: 5,7-dihydroxy-4′-methoxyflavylium chloride, 5,7-dihydroxy-4-methyl-4′-methoxyflavylium chloride and 5,7-dihydroxy-4-phenyl-4′-methoxyflavylium chloride. Malvidin 3,5-diglucoside lost colour slower than malvidin 3-glucoside and flavylium colour stability was in the order 4-phenyl>4-methyl>4-H. The results demonstrate that anthocyanin reactivity and the status of the flavylium 4-substituent play an important role in colour stability under these conditions.