Concentration Optimized Fish Gelatin/Metal-Phenolic Network Coatings With Enhanced Interfacial Adhesion and Barrier Properties for Mango Preservation

Mango, as a highly perishable climacteric fruit, incurs significant postharvest losses due to rapid ripening and spoilage. To address this challenge, environmentally friendly bioactive coating technology has emerged as a promising preservation strategy. This study developed a novel coating based on fish gelatin (FG), enhanced by a metal-phenolic network (MPN) formed through the coordination between tannic acid (TA) and Fe 3+ ions. By systematically optimizing the molar ratio of TA to Fe 3+ , the formulation with a 0.2% Fe 3+ concentration (FG/MPN 2 ) was identified as optimal, exhibiting the best system stability (zeta potential: +16.32 ± 1.21 mV) and micro-uniformity (PDI < 0.3). Structural analyses via Fourier-transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy confirmed the formation of a stable composite structure within the FG matrix. Benefiting from this, the FG/MPN 2 coating demonstrated significantly enhanced barrier properties, interfacial adhesion, and excellent antioxidant activity. Finally, the coating was applied to mango preservation (25°C, 60% RH). The preservation results indicated that the coating could significantly inhibit weight loss, maintain higher fruit firmness (17.92 ± 0.50 N) on the 12th day, effectively delay color yellowing, and reduce lipid peroxidation damage, thereby extending the shelf life.