Nano Emulsion of Essential Oils Loaded in Chitosan Coating for Controlling Anthracnose in Tomatoes (Solanum lycopersicum) During Storage

Tomato fruit is susceptible to decay caused by Colletotrichum gloeosporioides. An edible coating derived from essential oils loaded into a chitosan polysaccharide polymer is a sustainable delivery approach to improve coating versatility and stability for reduced reliance on synthetic fungicides to combat anthracnose incidence in tomatoes. The objective of this study was to evaluate the antifungal efficacy of nanostructured thyme essential oil incorporated into chitosan coatings [Nano-(T)-EO-CS] against Colletotrichum gloeosporioides in tomato fruits, and to investigate the underlying mechanisms contributing to its inhibitory effects. Nano-(T)-EO of (1% v/v) showed the greatest antifungal activities while achieving complete inhibition of C. gloeosporioides. At (0.8% w/v) concentration, chitosan inhibited 78% of radial mycelial growth in C. gloeosporioides. Loading Nano-(T)-EO (1% v/v) into chitosan (0.8% w/v) completely inhibited spore germination (100%). The surface electron microscopy revealed that the Nano-(T)-EO-CS coating induced significant deformation and inhibited the growth of C. gloeosporioides. Compared with the control, the Nano-(T)-EO-CS coating reduced disease incidence by 50%, whereas the commercial antifungal agent Sporekill&reg: reduced incidence by 40% in preventively inoculated tomatoes stored at 10 &deg:C and 85% relative humidity (RH) for 14 days after harvest, and at 18 &deg:C for 3 days at the market shelf condition. Despite chitinase activity peaking on day 14 of cold storage, it peaked significantly on day 7 in Nano-(T)-EO-CS and Sporekill&reg:-treated tomatoes. The Nano-(T)-EO-CS coating enhanced ferric-reducing antioxidant power and total phenol content in tomatoes for 7 and 14 d of postharvest storage. The chitosan-based edible coating loaded with thyme essential oil offers a sustainable, eco-friendly alternative to chemical fungicides for improving tomato shelf life and reducing decay.