INTERACTIONS BETWEEN CATECHIN AND MALVIDIN-3-MONOGLUCOSIDE IN MODEL SOLUTIONS

The interaction between (+)-catechin and malvidin-3-monoglucoside was studied in model solutions at pH values of 3.2 and 4 over a 30-day per iod at 32 degrees C. With time, a progressive browning, accompanied by a hypsochromic shift in their visible absorption maxima, was observed in the solutions. This was attributed to the formation of yellow pigm ents showing spectra with absorption maxima ranging between 425 nm and 455 nm, as detected by HPLC/DAS. A mechanism is proposed for the form ation of these pigments, according to which the anthocyanin in flavyli um form would bind through its C-4 to C-8 of catechin to give a colour less condensed flavene, which through an oxidative mechanism would lat er become rear-ranged to a xanthylium-like derivative. A degradation p rocess of the anthocyanin was seen to overlap that of condensation. Sy ringic acid was detected as being released from the anthocyanin degrad ation. When the solutions were conserved at 15 degrees C, all the proc esses were reduced and minor modifications occurred during the assay p eriod.