Influence of Chilling and Heating Stress On Oxidative Parameters and Antioxidant Systems in Tomato

‘Tasti-Lee’ and ‘Sanibel’ tomatoes were chilled at 5 °C air for 4 day or heated at 52 °C water for 15 min. Oxidative parameters, antioxidant compounds and antioxidant-related enzymes in the tomatoes were measured immediately after treatment and four days after transfer to 20 °C. For ‘Tasti-Lee’, heating did not affect content of malondialdehyde (MDA), an indicator of lipid peroxidation, or hydrogen peroxide (H₂O₂). Ascorbic acid (ASA), dehydroascorbate (DHA), glutathione (GSH) and oxidized GSH (GSH disulfide, GSSG) remained unchanged or slightly decreased. The activities of enzymes, related to scavenging of reactive oxygen species (ROS), such as superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase (POD) and catalase (CAT), and related to ASA-GSH cycle, such as monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR), were induced by heating treatment. However, chilling increased MDA content, and decreased content of ASA, DHA and GSH. Chilling also induced the ROS scavenging-related enzyme activities, but did not affect or slightly inhibited ASA-GSH cycle-related enzymes. For ‘Sanibel’, chilling also increased MDA content. Heat treatment reduced ASA and DHA levels, although it induced the activities of POD, CAT, DHAR and GR. The results indicate that both heating and chilling induced ROS scavenging-related enzymes, and protected the tissue from ROS. Heating also induced the activities of ASA-GSH cycle-related enzymes, thus maintaining ASA, DHA and GSH contents and the antioxidant capacity of tissue to counteract oxidative stress. This is also why heating often is used as a pre-treatment before storage to improve the storability of fruits and vegetables and protect against chilling injury. On the other hand, chilling caused loss of antioxidant capacity by inhibiting ASA-GSH cycle related enzymes, and decreasing ASA, DHA and GSH contents.