Effects of melatonin treatment on maintenance of the quality of fresh-cut pitaya fruit

The present work investigated the effects of different concentrations of melatonin (0, 50, 100, and 200 μmol L-1) on the quality and antioxidant activity of fresh-cut pitaya (Hylocereus undatus) fruits. Results revealed that melatonin treatments significantly increased the firmness, total soluble solids, and titratable acidity of post-harvest fruits, and inhibited the rate of weight loss. When compared with the control treatment, the application of melatonin maintained higher contents of vitamin C and total phenolics in fresh-cut pitaya fruits during storage. Melatonin also decreased cell membrane electrolyte leakage and polyphenol oxidase activity, with 100 μmol L-1 melatonin treatment showing the best effects. In addition, 100 μmol L-1 melatonin significantly increased the activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and peroxidase (APX), thus decreasing the accumulation of H2O2 and O2- during storage. Collectively, these findings indicate that melatonin treatment could contribute to delaying the ripening and senescence of fresh-cut pitaya fruits, and has potential application in the preservation of fresh-cut pitaya fruits during storage.