Effects of postharvest hot air treatments on the quality and antioxidant levels in tomato fruit

'Rhapsody' tomatoes heated for 24 h in air at 34 or 38 °C were compared to fruit heated in 5% O2 at 38 °C in order to determine if heat treatment applied in reduced O2 pressure might reduce stress-related oxidative changes that sometimes accompany heat injury. Fruit were subsequently stored at 4 or 10 °C for up to 30 d. Unheated fruit and those heated in air at 34 °C for 24 h developed the best colour during storage at 10 °C. Storage at 4 °C inhibited carotenoid development in all treatments. Fruit heated in air or in 5% O2 lost the most ascorbic acid and isoascorbic acid. Glutathione reductase activity at the end of storage was similar in all fruit, while glutathione S-transferase activity was higher in fruit that had initially been heated in 5% O2. Heating of 'Rhapsody' tomato fruit in air at 34 °C for 24 h prior to storage at 10 °C for up to 30 d resulted in the least losses in antioxidant content, and fruit colour developed adequately. Reduced O2 neither improved the efficacy of the heat treatment in reducing chilling injury nor protected tomato fruit from the negative effects of heat treatment.