Effect of ozone on oxidative stress defense enzymes and quality changes in tangerine (Citrus reticulata blanco cv. Sai Nam Pung) fruit

Abstract

The effect of ozone on oxidative stress defense enzymes and quality changes in tangerine (Citrus reticulata Blanco cv. Sai Nam Pung) fruit were studied. The fruits were either not wounded and non-inoculated or wounded and inoculated with Penicillium digitatum (1.04×105 spores ml-1) and then fumigated with ozone (200 ppm) for 0, 0.5, 1, 2, 4 or 6 hours and stored at 25±2°C for 7 days. Samples were taken everyday for investigation on oxidative stress defense enzymes activity (superoxide dismutase, peroxidase and catalase), some physical qualities (fruit firmness, weight loss and peel color) and chemical qualities (total soluble solids, titratable acidity and ascorbic acid content) changes. The results showed that exposing fruit to ozone for 4 and 6 hours delayed the disease incidence in inoculated fruit. One day after ozone fumigation, the activities of superoxide dismutase, peroxidase and catalase in the fruit peel were increased, especially in the 4 and 6 hour treatments. Throughout the 7 days of the experiment, the physical and chemical qualities of tangerine fruit in all treatments were not affected by ozone exposure. The results suggest that exposing fruit to ozone was effective in controlling postharvest disease and can increase superoxide dismutase, peroxidase and catalase activities.