Melatonin treatment reduces qualitative decay and improves antioxidant system in highbush blueberry fruit during cold storage

BACKGROUND: Blueberry is considered as a 'functional food' because it contains bioactive compounds such as flavonoids, phenolic acids, tannins and anthocyanins. The blueberry is one of the most consumed berries in the world and is highly appreciated by consumers because of its unique taste and sensory properties. Fresh blueberries decay rapidly because of mould and water loss. To preserve the qualitative and nutraceutical traits of fresh highbush blueberries during storage, the efficacy of 1 mm melatonin treatment was investigated at 5 °C for 3 weeks. RESULTS: The results demonstrated that melatonin treatment reduced weight loss and delayed postharvest ripening. Compared to the control, melatonin treatment induced an overproduction of polyphenols, flavonoids, anthocyanins and ascorbic acid, consequently increasing antioxidant activity. The enzymatic antioxidant system was also affected by the treatment. An increase in the activity of catalase, superoxide dismutase and ascorbate peroxidase was observed in treated fruit compared to that in control fruit. Enzymatic browning, controlled by assaying the content of malondialdehyde and hydrogen peroxide, polyphenol oxidase, guaiacol peroxidase and lipoxygenase activities, appeared to slow down under melatonin treatment. CONCLUSION: Melatonin coating is a valid tool for delaying the perishability and qualitative decay of highbush blueberry fruit during cold storage. Furthermore, this treatment increases the production of secondary metabolites such as polyphenols, flavonoids, anthocyanins and ascorbic acid, improving the nutraceutical traits of this fruit during storage. Melatonin treatment can be considered as an environmentally sustainable, non-harmful-to-human-health alternative for the postharvest preservation of highbush blueberry fruit. © 2022 Society of Chemical Industry.