Reactivity of (+)-catechin in wine-like hydroalcoholic solution in the presence of free and sulfite-bound aldehydes.

Aldehydes are generated during wine fermentation and oxidation and react with flavonoids under these conditions. These reactions affect wine quality by forming bridged oligomers and stable pigments that influence color and mouthfeel. Aldehydes also react with sulfites to form α-hydroxysulfonates under wine-like, hydroalcoholic conditions. This study examined the reactivity of formaldehyde, acetaldehyde, propionaldehyde, isobutyraldehyde, and benzaldehyde with (+)-catechin in hydroalcoholic solution under acidic (pH 2) conditions to accelerate reaction rates. The corresponding bisulfite adducts (α-hydroxyalkylsulfonates) were synthesized and similarly studied to reflect possible aldehyde speciation under wine conditions. (+)-Catechin consumption in treatments containing aldehyde-bisulfite adducts correlated with previously reported dissociation constants, suggesting that adduct stability influences aldehyde availability. In separate product mapping experiments (no bisulfite; aldehyde 5 mM), MALDI-TOF MS of catechin reaction mixtures tentatively identified bridged oligomers (DP 2-9).