Effects of Exogenous Melatonin Treatment on the Storage Quality and Antioxidant Capacity of Spaghetti Squash

In order to explore the effects of postharvest exogenous melatonin (MT) treatment on the storage quality of spaghetti squash, squash was treated with 0.2 mmol/L MT solution to investigate the changes in fruit quality and antioxidant capacity during storage at (9±1) ℃ with relative humidity of 65%~70%. The results showed that MT treatment delayed the occurrence of decay of spaghetti squash by 40 days during storage compared with the control group. At 160 d of storage, the decay rate of MT-treated fruit was only 15.56%, which was significantly lower than that of the control fruit (34.07%). At the end of storage, compared with the control group, MT treatment reduced the weight loss rate and respiration rate of fruits by 29.68% and 18.02%, respectively, and delayed the degradation of hardness, brittleness and color. In addition, MT treatment increased the peak activity of superoxide dismutase in fruits by 14.18% and effectively enhanced the activities of catalase, peroxidase and ascorbate peroxidase, reduced O₂⁻· production rate, significantly inhibited the accumulation of H₂O₂ and malondialdehyde. MT treatment also significantly enhanced total phenolics and ascorbic acid contents, enhanced the scavenging capacity of DPPH·, ABTS⁺· and ·OH. Comprehensive analysis indicated that postharvest MT treatment could effectively enhance the antioxidant capacity and maintain the better quality of spaghetti squash during storage.