Kinetic analysis of the stability of antioxidants in blackberry (Rubus fruticosus L.) liquor

The kinetic analysis of the stability of monomeric anthocyanins, ascorbic acid and antioxidant capacity of blackberry (Rubus fruticosus L.) liquor was performed as well as physicochemical evaluation of fresh fruit and liquor. °Brix, pH, titrable acidity, density and moisture content were evaluated for fresh fruit and results were similar to reported ones. Liquor was characterized during 180 days of aging in term of its physicochemical properties. Contents of monomeric anthocyanins (ACyMon) and ascorbic acid in backberry liquor agreed with reported data but kinetics of their change during aging has not yet been published. A first order kinetics described (R² >90%) decrements of anthocyanins, ascorbic acid and antioxidant capacity. ACyMon, polymeric colour, total phenols, antioxidant capacity and ascorbic acid correlated well (R >0.7) with each other. Rate constants and half-life time for anthocyanins showed that they were more prone to degradation than ascorbic acid and antioxidant capacity which decreased slower than anthocyanins and ascorbic acid, having a half-life time of 630.13 days. It was noteworthy that the relative rate of loss of ascorbic acid and total anthocyanins in relation to antioxidant capacity are both higher than 1 (4.54 and 5.09 respectively), due to the existence of other reactive species such as phenols that contributed to antioxidant capacity.