Products Formed in Model Wine Solutions Involving Anthocyanins, Procyanidin B₂, and Acetaldehyde

Interaction between anthocyanins (3-glucosides of cyanidin, peonidin and malvidin), procyanidin B2 (B2), and acetaldehyde and the formation of new colored compounds was studied in model wine solutions. The anthocyanin−procyanidin B2 condensation reaction showed first-order kinetics with or without the presence of acetaldehyde, and the reaction rates were calculated. In all the model solutions containing anthocyanins, procyanidin B2, and acetaldehyde, rapid color augmentation with shifts toward violet were observed. Two principal new compounds (thought to be trimers, linked at different positions) were detectable by HPLC, and their spectral properties were studied by diode-array spectroscopy. Malvidin 3-glucoside reacts more slowly than cyanidin 3-glucoside and peonidin-3 glucoside. Similar color changes were observed in model solutions containing anthocyanins alone with acetaldehyde. Finally, we observed that the degradation constant rates for each anthocyanin increased in the following order: anthocyanins alone < anthocyanins + B2 < anthocyanins + acetaldehyde < anthocyanins + B2 + acetaldehyde. Similar increasing order of the reaction rates of procyanidin B2 was observed. In both cases, the presence of acetaldehyde was of major importance in accelerating the chemical transformation of phenolic compounds, inducing the formation of new products. Keywords: Anthocyanins; procyanidin B2; acetaldehyde; condensation reaction