Development and characterization of potato starch/sodium alginate active composite films incorporated with theabrownin and their application in fresh Auricularia auricula-judae preservation

Bioactive films based on polysaccharides incorporated with theabrownin were developed. • Theabrownin improved UV barrier and antioxidant activity of films. • The addition of theabrownin significantly enhanced the mechanical properties of films. • The films can effectively extend the shelf life of fresh Auricularia auricula-judae . In this study, theabrownin (TB) was extracted from Tibetan tea and characterized using active functional groups including hydroxyl and carboxyl groups, exhibits a porous and wrinkled surface morphology, displays a characteristic absorption peak around 200 nm, and demonstrates significant antioxidant capacity. Based on these findings, composite films of potato starch (PS)/ sodium alginate (SA) with varying TB content were prepared by solution casting. When the TB content was 7.5%, the composite film exhibited optimal overall performance: the water vapor transmission rate decreased to 173.87 g/(m 2 ·24 h), the oxygen transmission rate was as low as 0.33 cm 3 /(m 2 ·24 h·0.1 MPa), the tensile strength increased to 16.89 MPa, and the specimen demonstrated substantial radical-scavenging capacity, DPPH and ABTS radical scavenging rate recorded at 61.26% and 64.38%, respectively. Furthermore, when applied to the preservation of fresh Auricularia auricula-judae , the composite film effectively inhibited weight loss, enzymatic browning, and overall quality deterioration after 13 days preserved at 4 °C, demonstrating favorable preservation effects. This study provides an effective strategy for the design of high-performance polysaccharide-based packaging materials, and broadens the approaches for the high-value utilization of tea extracts in the field of green packaging.