Biodegradable Tea Saponin/Xylan/PVA Composite Films with Antibacterial and Antioxidant Properties for Strawberry Preservation

Conventional non-degradable plastic films used in postharvest packaging cause environmental pollution and offer limited functionality for extending shelf life. The booming Camellia oleifera oil industry generates massive tea shell waste, whose improper disposal is both a resource loss and an opportunity for developing biodegradable active packaging. Here, alkali-extracted xylan (AX) and tea saponin (TS) were blended with PVA to prepare TS/AX/PVA composite films. The optimized films exhibited low moisture content (10.39%), reduced water solubility (0.35%), enhanced UV-blocking and water vapor-barrier properties, near-complete visual disintegration within 30 days of soil burial (visual soil-burial assessment only), and elongation at break up to 330.81%. The incorporation of AX improved the mechanical strength and degradability of the PVA matrix, while TS imparted antioxidant and antibacterial activities, yielding better hydrophobicity, higher tensile strength, and enhanced antibacterial performance than neat PVA. In fresh strawberry preservation, the 6% TS/AX/PVA film retarded quality deterioration, maintaining 18.43% lower relative conductivity than the control, 0.51% titratable acidity, and 26.64 mg/100 g vitamin C (71.21% higher than the PE group) on day 10. This study converts agricultural by-products into biodegradable functional films and suggests a plausible, but not directly measured, preservation mechanism that requires verification, offering a promising substitute for conventional packaging plastics.