Reactions of Monomeric and Polymeric Flavan-3-ols with Monomeric Pigment in Model Wine Solutions

Pinot noir seeds contain a greater proportion of monomeric flavan-3-ols (catechins) to polymeric flavan-3-ols (tannin) than do Cabernet Sauvignon seeds. As Pinot noir wines are typically less tannic than Cabernet wines, it was hypothesized that the "excess" catechins were preferentially reacting with monomeric anthocyanins, preventing the formation of the anthocyanin-tannin adduct which serves to solubilize tannin. Competition studies in model wine solutions, however, showed that for monoglucosidic anthocyanins the catechins were not competing with tannin in the formation of an anthocyanin adduct, but rather that the catechins and tannin were preferentially reacting with each other in a dynamic process of interflavan bond formation and breakage. However, for diglucosidic anthocyanin the catechins did react preferentially to the tannin in the formation of the adduct. The putative stabilizing mechanism of monoglucosidic anthocyanin and tannin condensation never occurred during the course of the experiment, supporting the contention that the time-course of this reaction is slow.