Anthocyanins: Colour augmentation with catechin and acetaldehyde

Solutions of anthocyanins became more violet and greatly increased in colour in the presence of catechin and acetaldehyde at pH 3.5. The colour changes were attributed to the formation of a range of highly coloured new compounds, some detectable by chromatography and believed to be formed by Baeyer‐type condensations. The reaction rates increased with increasing concentration ratio of catechin to anthocyanin. Anthocyanidin 3,5‐diglucosides reacted more slowly than 3‐glucosides, gave smaller violet shifts and their augmented colours were more stable. A small amount of a new anthocyanin derived from delphinidin 3‐glucoside was isolated and its properties examined.