REDUCTION OF FREE RADICAL CONTENT AND CHILLING INJURY IN 'NAM DOK MAI NO. 4' MANGO FRUIT WITH METHYL JASMONATE DURING LOW TEMPERATURE STORAGE

Abstract

The effects of methyl jasmonate (MJ) on free radical content, antioxidant capacity and chilling injury (CI) of ‘Nam Dok Mai No. 4’ mango fruit during low temperature storage were investigated. Mango fruits were dipped in 0.1 mM MJ aqueous solution and distilled water (control) for 10 min and stored at 5°C for 42 days. They were sampled every seven days to determine superoxide radical (O2●-), hydrogen peroxide (H2O2) and hydroxyl radical (OH●). Total antioxidant capacities by 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging activity and CI index were also measured. It was shown that low temperature storage promoted free radical accumulation by gradual increase of O2●-, H2O2 and OH● contents with storage time. However, both antioxidant capacities increased and reached the peak on day 21 and decreased thereafter. CI occurred on day 21 and then rapidly increased. CI symptom development appeared slower than free radical accumulation and antioxidant responses. Treatment with MJ significantly lowered free radical accumulation and enhanced antioxidant capacity associated with a reduction in the percentage of surface area affected by browning and pitting on the peel (CI index). Correlations between CI and free radical content and between CI and antioxidant capacity were highly significant. These results indicated that low temperature stress induced free radical accumulation, which resulted in CI development. MJ treatment can reduce CI of mango fruit by activating the fruit defense responses as indicated by the decrease in free radical content and increase in antioxidant capacity.