Sodium alginate-green synthetic nano-silica/chitosan-thyme essential oil bilayer film for tomato preservation.

A chitosan (CS)/sodium alginate (SA)-based bilayer composite film (CTSS-40) incorporated with silicon dioxide nanoparticles (SiO₂ NPs) green-synthesized from Rosa roxburghii and thyme essential oil was fabricated to enhance tomato preservation. SiO₂ NPs greatly improved film performance, especially at 0.4 g L-1. CTSS-40 film reduced water-vapor and oxygen permeability by up to 63.39% and 62.37% and increased tensile strength by up to 1.21-fold compared with CS, SA monolayer, and CS/SA bilayer films, respectively. In vitro, CTSS-40 showed enhanced antifungal activity, with inhibition zones against Alternaria alternata and Colletotrichum gloeosporioides increased by 54.11% and 72.78% compared to CS film, respectively. After 20 days of storage, CTSS-40 reduce decay index by 61.88% compared to uncoated fruits. CTSS-40 significantly reduced respiration intensity and ethylene release, retarded quality deterioration, and maintained high activities of antioxidant and defense-related enzymes and free radical scavenging capacity. Collectively, CTSS-40 bilayer film provides an effective and eco-friendly fruit preservation strategy.