Ascorbic acid-induced browning of (+)-catechin in a model wine system

The ability of ascorbic acid to induce browning of (+)-catechin in a model wine system has been studied. A significant increase in absorbance at 440 n m was observed over 14 days when ascorbic acid was incubated at 45 degreesC with (+)-catechin in a model wine base. The onset of browning was delayed for about 2 days, although the length of the lag period was dependent on th e amount of molecular oxygen in the headspace of the reaction system. The l ag period was not observed when a preoxidized solution of ascorbic acid was used, suggesting that a product of ascorbic acid oxidation is responsible for the onset of browning. Hydrogen peroxide, when added directly to (+)-ca techin in the model system, was not capable of producing the same degree of browning as that generated by ascorbic acid. Liquid chromotography evidenc e is presented to show that different reaction products are produced by asc orbic acid and hydrogen peroxide.