Preparation and characterization of biodegradable films based on chitosan/poly(vinyl alcohol) incorporating selenium-immobilized graphene oxide for fruit preservation

Postharvest microbial contamination and moisture loss significantly shorten the shelf life of fresh produce, creating demand for biodegradable films with integrated antibacterial function. In this study, a three-component film composed of chitosan (CTS), poly(vinyl alcohol) (PVA), and graphene oxide-based selenium (SeGO) was fabricated via solution casting. Selenium microparticles were synthesized using Psidium guajava leaf extract and anchored onto graphene oxide sheets through ex situ ultrasonication. The combined effects of CTS, PVA, and SeGO on antibacterial activity against Escherichia coli were optimized using Response Surface Methodology based on a Box–Behnken design. The optimal ratio (CTS:PVA:SeGO = 2:4:2) achieved 99.99% inhibition, consistent with the predicted value (p < 0.05). Structural and physicochemical properties were characterized by FTIR, SEM-EDS, XRD, mechanical testing, swelling, and water vapor permeability analyses. The optimized film exhibited superior antibacterial performance compared with CTS, CTS-PVA, and CTS-SeGO films. In postharvest evaluation, Manilkara zapota coated with the optimized film showed reduced weight loss and no fungal growth after 6 days of storage. These findings demonstrate the potential of CTS/PVA/SeGO films for sustainable food packaging applications.