White mulberry (Morus alba L.) fruit is a rich source of bioactive compounds, but it is highly perishable and vulnerable to browning. In the current study, melatonin at concentrations of 0, 125, 250, 500, and 1000 µM was sprayed on mulberry fruit and stored at 1 °C for 12 d. Melatonin treatment yielded the lowest browning index during storage time. This reduction was accompanied by a significant decrease in malondialdehyde, H2O2 and polyphenol oxidase enzyme activity. The results showed that melatonin reduced weight loss and maintained pH, as well as total soluble solids. Furthermore, the total phenol, total flavonoids and ascorbic acid contents in treated fruit were significantly higher than in an untreated fruit, which was accompanied by an increase in antioxidant capacity. With assuming 40% browning would render the fruit unmarketable, melatonin treatments could extend mulberry storage life beyond 8 days. The 500 and 1000 μM melatonin treatments showed the most effective results. In conclusion, exogenous melatonin application can be considered a safe and promising procedure to maintain the quality of mulberry fruit during low-temperature storage.
