Tissue Localization Effect on Antioxidant Metabolism of 1-MCP Treated Flesh Browning of ‘Empire' Apples

During CA storage, flesh browning is sporadically detected in ‘Empire’ apples and also, it is much frequently occurred at the shoulder of stem-end localized tissues. The objective of this study was to investigate the tissue localization effect of 1-MCP treated flesh browning on antioxidant scavenging systems of ‘Empire’ apple fruit stored at 2 kPa O₂/2 kPa CO₂ at 3.3 °C for up to 40 weeks. 1-MCP did not affect the incidence of flesh browning but reduced lightness values (L*) and hue angle (h°) at the end of storage. The decrease of these values was more significant at the stem-end localized tissues than at the calyx-end ones. 1-MCP reduced nitroblue tetrazolium (NBT) reducing activity but increased H₂O₂ concentration. Although 1-MCP did not affect malondialdehyde (MDA) level, MDA concentration was lower at calyx-end tissue than at stem-end one. The concentrations of ascorbic acid (AsA) and glutathione (GSH) were reduced over storage regardless of 1-MCP treatment and also, calyx-end localized tissue had a much higher concentration of AsA and GSH than stem-end tissue. While ascorbic peroxidase (APX) activity was not affected by 1-MCP treatment, its activity in untreated one was significantly lower at stem-end tissue than at calyx-end localized tissue. The activities of superoxide dismutase (SOD) and copper/zinc-superoxide dismutase (Cu/Zn-SOD) were increased as the NBT reducing activity increased. The activities of catalase (CAT) and peroxidase (POX) were reduced by 1-MCP treatment but the other enzyme activities were inconsistent. Therefore, the results indicated that there was no strong evidence to support that 1-MCP might cause to develop the flesh browning but the stem-end localized tissue could be more susceptible to the flesh browning due to the lower concentrations of AsA and GSH.