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-ol s (catechins) to polymeric flavan-3-ols (tannin) than do Cabernet Sauv ignon seeds. As Pinot noir wines are typically less tannic than Cabern et wines, it was hypothesized that the ''excess'' catechins were prefe rentially reacting with monomeric anthocyanins, preventing the formati on 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 tan nin in the formation of an anthocyanin adduct, but rather that the cat echins and tannin were preferentially reacting with each other in a dy namic process of interflavan bond formation and breakage. However, for diglucosidic anthocyanin the catechins did react preferentially to th e tannin in the formation of the adduct. The putative stabilizing mech anism of monoglucosidic anthocyanin and tannin condensation never occu rred during the course of the experiment, supporting the contention th at the time-course of this reaction is slow.