Flavanol-anthocyanin adduct
Flavanol-anthocyanin adducts are formed during wine ageing through reactions between anthocyanins and tannins present in grape, with yeast metabolites such as acetaldehyde. Acetaldehyde-induced reactions yield ethyl-linked species such as malvidin glucoside-ethyl-catechin.
This type of compound has a better color stability at pH 5.5 than normal anthocyanins. When the pH was increased from 2.2 to 5.5, the solution of the pigment became progressively more violet, whereas similar solutions of the anthocyanin were almost colorless at pH 4.0.
