Application of Cu2+-chelated curcumin/chitosan coating in maintaining the storage quality of harvested passion fruit.

Passion fruit is susceptible to postharvest spoilage, requiring innovative preservation strategies. This study developed a novel Cu2+-chelated curcumin/chitosan composite coating (CuCur-CS) via self-assembly. Under ambient temperature, CuCur-CS treatment was the most effective, exhibiting the lowest weight loss rate (only 5.6% on day 18), along with superior fruit shape and surface color retention. The coating stabilized sugar-acid balance by suppressing respiration and alleviating oxidative stress. By day 18, H2O2 and MDA contents in the control increased by 53% and 28%, respectively, versus only 11% and 12% in CuCur-CS. Metabolomics revealed that CuCur-CS attenuated energy metabolism by stabilizing TCA cycle intermediates, while modulating phenylpropanoid and fatty acid pathways to suppress volatile alcohols, esters, and excessive phenolics and flavonoids. These actions delay aroma degradation and prevent antioxidant overactivation. Overall, CuCur-CS effectively retards senescence and postharvest losses, offering a promising preservation solution for passion fruit.