Ascorbic acid degradation in orange, grape and pomegranate juices, and sour cherry nectar was studied at 20, 30 and 40 degreesC, with or without the addition of hydrogen peroxide (H2O2). Analysis of kinetic data suggested that the degradation fitted better to a zero-order model than a first-order model. Rate constants increased slightly in the presence of 0.5 pprn H2O2. However, increasing H2O2 concentration from 0.5 to 5 ppm caused a substantial increase in the degradation rates of ascorbic acid. Anthocyanins markedly accelerated the degradation of ascorbic acid in sour cherry nectar and pomegranate juice, especially at 5 ppm H2O2 concentration. Degradation was slowest in orange juice, with or without the addition of H2O2. Activation energies were lowest for grape juice (26.2 U mol(-1)) and highest for pomegranate juice (71.0 kJ mol(-1)) in the presence of 0.5 ppm H2O2. (C) 2004 Elsevier Ltd. All rights reserved.