Kinetic analysis of anthocyanin degradation and polymeric colour formation in grape juice during heating

The degradation of total monomeric anthocyanins and changes in the proportion of polymeric colour (% PC) as well as antioxidant capacity of grape juice were studied during heating at 70-90°C. Anthocyanin degradation fitted to a first order reaction model, while the formation of % PC followed zero order reaction kinetics. High correlations (r = 0.989-0.997) were found between anthocyanin degradation and % PC formation during heating. The activation energies for the degradation of anthocyanins and formation of % PC were 64.89 and 50.42 kJ/mol, respectively. Trolox equivalents antioxidant capacity (TEAC) values of grape juice slightly changed during heating.