Postharvest salicylic acid and melatonin dipping delay ripening and improve quality of 'Sensation' mangoes

Freshly harvested mature-green 'Sensation' mangoes were dipped for 10 min in 2 mM salicylic acid (SA) and 0.2 mM melatonin (MT) alone or in combination and stored at 23+-1deg C and 60–70%RH. SA or MT delayed ripening measured as higher green peel color (lower a* values), firmness, titratable acidity (TA) and membrane stability index (MSI) and lower weight loss, total soluble solids (TSS), TSS/TA ratio and hydrolytic enzyme activities (polygalacturonase, xylanase and alpha-amylase) compared to that of untreated fruit. Total phenolic content (TPC) in peel of treated fruit increased with fluctuations during ripening and was higher than the control. In pulp, TPC decreased up to 6 days but increased thereafter, and was higher in treated fruit than the control. Total flavonoid content (TFC) in the peel decreased while that in the pulp increased with fluctuations during ripening and was higher in treated fruit than the control. Vitamin C content decreased during ripening and was not affected by the treatments. DPPH radical scavenging capacity (RSC) in peel decreased during ripening and was higher in treated fruit than the control. However, RSC in pulp increased during ripening and was not affected by treatments, except for SA plus MT treatment that gave higher RSC than the control after 6 and 10 days. Polyphenoloxidase (PPO) activity increased during ripening and was lower in treated fruit than the control. Peroxidase (POD) activity increased during ripening and was higher in treated fruit than the control. SA and MT combination treatment provided no additional positive effects on most parameters. It is concluded that postharvest dipping in 2 mM SA or 0.2 mM MT delayed ripening and improved quality of 'Sensation' mangoes via inhibiting hydrolytic enzymes and enhancing antioxidant system of fruit and are suggested as natural alternative to synthetic chemicals.