Edible Fe2ZnO4 nanocomposites prolong shelf life and control black mold rot in table grapes: Enzymatic mechanisms

The perishable nature of grapes leads to significant pre- and postharvest losses from fungal infections and the decay accelerated by ethylene, enzymatic browning, senescence, and microbial growth. Herein, a Fe₂ZnO₄ nanocomposite (70.22 nm) was developed with defence-related enzyme activities to suppress black mold decay in postharvest table grapes. The edible Fe₂ZnO₄ coating delayed in vitro mold growth and reduced infections by Aspergillus carbonarius in table grapes stored at room temperature. The effects of the coatings on antioxidant enzyme activities of A. carbonarius, as well as physicochemical and defence-related enzyme activities of table grapes, were assessed. The activities of defence-related enzymes, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and enzymes of the alkaline phosphatase (APX), phenylalanine ammonia (PAL) and polyphenol oxidase (PPO), were significantly higher in table grapes coated with Fe₂ZnO₄ nanocomposite compared to the control, individual FeO or ZnO treatments by day 5. Natural decay analysis and quality parameters showed that the Fe₂ZnO₄ nanocomposite coating effectively maintained fruit quality during storage. Its inhibitory mechanism of Fe₂ZnO₄ nanocomposite on black mold decay in table grape fruit may be associated with the direct fungi toxic property against the A. carbonarius. These findings indicate that Fe₂ZnO₄ nanocomposite directly inhibited A. carbonarius via fungicidal effects while simultaneously disrupting fungal anti-ROS mechanisms and activating grape defence systems, subsequently controlling black mold.