Optimization of fumed silica and melatonin loadings in polyvinyl alcohol-based films for postharvest preservation of rambutan fruit

To address high hydrophilicity of polyvinyl alcohol (PVA) and agglomeration tendency of fumed silica (FS), melatonin (MT)-functionalized PVA/FS composite films were prepared to enhance their performance and applicability. MT (1–3%) mitigated FS aggregation and promoted interfacial adhesion, forming a denser network. The P/S-M2 (2% MT) film exhibited the best performance among all tested films, showing a 17.4% increase in tensile strength, an 88.1% decrease in water vapor permeability, and reductions of 78.8%, 46.0%, and 32.6% in moisture content, water solubility and swelling ratio, respectively, compared to the P/S film. The P/S-M2 film also demonstrated enhanced biodegradability (74.7% degradation after 120 days) and antioxidant activity (85.3% ABTS radical scavenging rate). Packaging application of composite films to rambutan fruit delayed the changes of weight loss, chromaticity L * and soluble solid contents, with the P/S-M2 film demonstrating the optimal effect. Overall, MT-functionalized PVA/FS films offer a promising packaging solution for rambutan preservation. • Melatonin (MT) acted as a novel dispersant in PVA/silica (P/S) composites. • Composite film containing 2% MT (P/S-M2) showed optimal mechanical/barrier traits. • P/S-M2 film demonstrated strong antioxidant activity and improved biodegradability. • P/S-M2 film as a packing agent exerted a good preservation effect on rambutan fruit.