Effect of exogenous melatonin on postharvest storage quality of passion fruit through antioxidant metabolism

This study investigated the effect of melatonin (MT) on postharvest storage quality of passion fruit. Passion fruits were treated with four different concentrations of MT solutions (100, 200, 300 and 400 μmol/L) for 30 min and stored for 8 days. Compared with the control, the optimal MT concentration (200 μmol/L) treatment significantly reduced the shrinkage index, browning index, weight loss, ethylene production, and respiration rate, and delayed the decline of firmness, total soluble solids (TSS), and color, thus maintaining the quality of postharvest fruits. Exogenous MT enhances antioxidant activity and reduces fruit oxidative damage by inhibiting the increase in pericarp cell membrane permeability, malondialdehyde (MDA) content, maintaining high ascorbic acid (AsA), total phenolics, and flavonoids content, and increasing superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and polyphenol oxidase (PPO) activities. These findings suggest that postharvest exogenous application of MT is effective in maintaining passion fruit quality and delaying senescence.