Synergistic antifungal and barrier performance of potassium sorbate-loaded agar–chitosan bilayer coatings for postharvest preservation of mango

Mango ( Mangifera indica L.) is highly susceptible to rapid postharvest deterioration and fungal infection, particularly anthracnose caused by Colletotrichum spp . This study developed multifunctional agar–chitosan bilayer coatings incorporating potassium sorbate (PS) as an active antifungal system for mango preservation. The bilayer architecture integrates the mechanical stability of agar with the antimicrobial functionality of chitosan, while PS enhances antifungal efficacy and barrier performance. Incorporation of PS significantly reduced water vapor transmission rate from 1.35 to 0.73 g.h −1 .cm −2 and improved UV-shielding properties, while slightly decreasing puncture resistance. The films exhibited strong, concentration-dependent antifungal activity, effectively inhibiting fungal growth. When applied to mango, PS-loaded coatings reduced weight loss, maintained firmness, delayed ripening, and suppressed anthracnose development during 7 days of ambient storage. Coatings containing 20–25% PS showed the highest preservation efficiency, resulting in minimal lesion formation and superior visual quality. The enhanced performance is attributed to the synergistic effects of chitosan-induced membrane disruption, sorbate-mediated metabolic inhibition, and improved barrier properties of the bilayer matrix. This study provides a promising strategy for designing biodegradable active coatings with enhanced antifungal functionality and highlights the potential of bilayer systems for sustainable postharvest preservation of tropical fruits.