Reactions Involved in Sulfite Bleaching of Anthocyanins

SUMMARY The bleaching of anthocyanins by sulfur dioxide is a reversible process that does not involve hydrolysis of the 3‐glycosidic group, reduction of the pigment, or addition of bisulfite to a ketonie, chalcone derivative. In sulfite decoloration the reactive species is the anthocyanin carbonium ion (R + ). The experimental evidence indicates that this simply reacts with a bisulfite ion to form a colorless chromen‐2 (or 4)‐sulfonic acid (R‐SO 3 H), similar in structure and properties to an anthocyanin carbinol base (R‐OH).