Unveiling the underlying mechanisms of chitosan-melatonin coating in preserving pomegranate arils-sacs quality

• Chitosan-melatonin (CH-MT) edible coating preserved quality attributes of aril-sacs. • CH–MT coating inhibited the accumulation of off-flavour volatile compounds. • CH–MT coating reduced the loss of desirable flavour volatile compounds. • CH–MT coating upregulated phenolic metabolites with strong antioxidant properties. • CH–MT-coated aril-sacs exhibited significantly higher antioxidant activity. This study evaluated the mechanisms of chitosan-melatonin (CH-MT) edible coating in preserving the postharvest quality of minimally processed pomegranate aril-sacs. Mature pomegranate fruits were harvested, processed into aril-sacs, and treated with a composite coating comprising CH (0.5 %) and MT (0.8 mM), while distilled water served as the control treatment. The aril-sacs were stored at 5 °C and 85 % relative humidity for 21 days. CH-MT-coated aril-sacs showed higher antioxidant capacity, as shown by higher DPPH, ABTS + , and FRAP. This heightened antioxidant potential was associated with elevated activities of phenylalanine ammonia-lyase, peroxidase and catalase, and the suppression of polyphenol oxidase enzyme activity. The CH-MT edible coating also promoted the accumulation of key metabolites such as caffeic acid and quinic acid methyl ester with potent antioxidant properties while inhibiting specific volatile compounds linked to off-flavors. These findings demonstrate the efficacy and mechanisms of CH-MT composite coating in maintaining the quality of pomegranate aril-sacs, thus presenting a robust strategy for enhancing the postharvest storability of fresh-cut produce.