Relationship of Superficial Scald in 'Fuji' Apples to Changes of Reactive Oxygen Species Metabolism in Response to Ventilation Treatment

'Fuji' apples stored at 0 degrees C under non-ventilated or ventilated air after harvest were used to investigate the responses of superficial scald susceptibility to reactive oxygen species (ROS) metabolism. Ventilation decreased the concentrations of a-farnesene and conjugated trienol in apples in comparison with static storage and conjugated trienols were correlated with scald development. In both treatments, the levels of O-2(-) and H2O2 increased during storage, whereas, ventilated apples kept higher Of but lower H2O2 contents than non-ventilated ones, which resulted in a positive relationship between O-2(-) and H2O2. The activities of antioxidant enzymes all peaked before/when scald appeared and decreased while scald sustainably developed. Superoxide dismutase and catalase activities were higher in non-ventilated than ventilated apples early in storage, but no significant difference was observed between two treatments during scald symptom expression. Difference of guaiacol peroxidase activities was only observed after 15 weeks. These results indicated that conjugated trienols and reactive oxygen species producedduring a-farnesene oxidation were related with scald development. It can be concluded that scald development is a long-term event induced by reactive oxygen species metabolism and could probably be aggravated by increased generation of reactive oxygen species, which attributes to the break of the balance between a-farnesene production and oxidation and antioxidative defense system during cold storage.