ANTHOCYANIN DEGRADATION IN OXIDIZING GRAPE MUSTS

White musts with added grape anthocyanis were prepared and oxidised us ing known amounts of oxygen. Although malvidin and peonidin glucosides were degraded at a slower rate than o-diphenolic anthocyanins, import ant losses of all pigments occurred in oxidising grape musts. Degradat ion was inhibited by glutathione in excess, meaning that enzymically g enerated quinones of caffeoyltartaric acid were involved in the degrad ation mechanisms. Addition of anthocyanins hardly modified the kinetic s of caffeoyltartaric acid oxidation and conversion to 2-S-glutathiony l caffeoyltartaric acid (grape reaction product). All musts browned co nsiderably during oxidation. Browning of white musts was measured as a n increase of redness (a) and a decrease of lightness (L*) and yellow ness (b and hue angle) whereas browning in anthocyanin added musts ap peared essentially as a loss of red colour (a).