Additive enhancement of biodegradability and antibacterial performance in thermoplastic starch/chitosan films incorporating oregano essential oil and silver-zinc oxide nanoparticles

This study presents a novel thermoplastic starch-chitosan composite film, enhanced with oregano essential oil and silver-zinc oxide (Ag-ZnO: 1%) nanoparticles, designed to overcome the limitations of conventional biopolymer packaging. The synergistic combination of these additives significantly improved mechanical strength (tensile strength: 72.86 to 98.72 MPa), stiffness (Young's modulus), and reduced water uptake by up to 25% compared to unmodified controls. Rigorous biodegradation tests under UV, soil, and aqueous conditions demonstrated accelerated environmental breakdown, with up to 39.53% weight loss after one month under UV exposure. Antimicrobial assays showed inhibitory activity against the tested microorganisms, with inhibition zones of 42 mm against Staphylococcus aureus and 33 mm against Escherichia coli. These results highlight the multifunctional advantages of integrating biopolymers, essential oils, and nanometallic agents, and support a rational strategy for developing sustainable food-packaging materials with improved physical, degradative, and antimicrobial performance.