Effect of Methyl Jasmonate Treatment on Postharvest Pericarp Browning of Longan Fruit

In this research, we investigated the effects of treatment with different concentrations (10, 50 and 100 μmol/L) of methyl jasmonate (MeJA) on postharvest browning of ‘Chuliang’ longan fruit (Dimocarpus longan Lour.) during storage at (20 ± 1) ℃ and 85% relative humidity. The results showed that compared with the control fruit, MeJA treatment effectively reduced pericarp browning index, pericarp cell membrane permeability and pulp breakdown index in a concentration-dependent manner. In addition, 100 μmol/L MeJA maintained higher contents of total phenols and flavonoids, reduced the activity of polyphenol oxidase (PPO), and increased the activity of peroxidase (POD) and phenylalanine ammonialyase (PAL) in the pericarp. MeJA treatment could effectively reduce the rate of superoxide anion production and H₂O₂ content, enhance the activity of antioxidant enzymes (superoxide dismutase (SOD) and catalase (CAT)) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity, and improve antioxidant capacity. Therefore, it is concluded that 100 μmol/L MeJA treatment can inhibit postharvest phenolic metabolism and increase antioxidant capacity in longan fruit, thus delaying pericarp browning and prolonging its storage.