Oxidative stress and antioxidant systems in tomato fruits stored under normal and hypoxic conditions

Tomato varieties ARTH-3 (long shelf life; 14-15 days) and Sel-7 (short shelf life; 5-7 days), harvested at colour turning stage, were stored in open trays, cardboard boxes and polyethylene bags at 25°C and sampled at two day intervals until complete deterioration. Polyethylene bags were sealed and so are expected to have low O₂ atmosphere as compared to open trays and cardboard boxes. Variety ARTH-3 could be stored for ten days while Sel-7 could not be stored longer than six days. In both the varieties, lipoxygenase (LOX) activity, malondialdehyde (MDA) value and H₂O₂ content increased during storage. Fruits stored in polyethylene bags displayed minimum increase in these indices of reactive oxygen species (ROS) followed by open trays and cardboard boxes. Activities of enzymes responsible for scavenging ROS viz., superoxide dismutase (SOD), peroxidase (POX), ascorbate peroxidase (APX), catalase (CAT) and glutathione reductase (GR) decreased continuosly during storage. Tomatoes stored in polyethylene bags exhibited maximum activities of these enzymes thus neutralizing the deleterious effect of ROS. Although in general, the fruits got deteriorated during storage, the overall physical appearance of the fruits stored in polyethylene bags was acceptable. These results suggest that fruits stored in polyethylene bags could tolerate oxidative stress and prevent the membrane damage and loss of tissue structure to a higher degree than the fruits stored in open trays and cardboard boxes.