UV-C Irradiation Enhances Antioxidant Capacity and Delays Postharvest Shrinkage of Passion Fruit

In response to the water loss, shrivelling, and oxidative ageing commonly observed in Golden passion fruit after harvest, this study systematically evaluated the regulatory effects of short-wave ultraviolet (UV-C) treatment. The results showed that UV-C treatment at 3.6 kJ m^-2 significantly curtailed the increases in weight loss and shrivelling index during storage. Low-field nuclear magnetic resonance (LF-NMR) analysis revealed that this treatment effectively maintained the stability of water distribution in fruit tissues by delaying the conversion of free water to bound water. Regarding antioxidant regulation, UV-C treatment significantly increased the activities of key antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR), while promoting the accumulation of non-enzymatic antioxidants, such as total phenols, total flavonoids, and ascorbic acid (AsA). These changes synergistically enhanced reactive oxygen species (ROS)-scavenging capacity, leading to significant reductions in H₂O₂ content and malondialdehyde (MDA) levels, thereby alleviating lipid peroxidation damage to cell membranes. Overall, UV-C treatment effectively maintained cell membrane integrity and regulated water migration through the coordinated regulation of enzymatic and non-enzymatic antioxidant defence systems, thereby delaying passion fruit shrivelling and improving postharvest quality and storage stability.