Gradient curdlan@Zn/chitosan@curcumin composite films by interfacial co-precipitation for enhanced fruit preservation

This study introduces a novel interfacial co-precipitation method for fabricating gradient-structured composite films from chitosan (CS) and curdlan (CDL). This technique spatially separates curcumin (CUR) from the alkaline CDL phase, preserving its vibrant yellow color and maintaining its antioxidant and antimicrobial efficacy. The developed CDL@Zn/CS@CUR films were systematically characterized, with the optimal 1:3 CS:CDL ratio yielding superior mechanical properties (tensile strength: 55.14 ± 0.92 MPa; elongation at break: 2.90 ± 0.20 %), enhanced thermal stability, and improved water repellency (swelling ratio: 253.24 ± 41.21 %; contact angle: 68.37 ± 1.12°). CUR incorporation significantly improved film elasticity and enhanced antioxidant and antimicrobial activities. Furthermore, these films effectively protected blueberries with reduced weight loss (up to 27.21 ± 3.86 %) and decay rate (up to 5.56 ± 2.27 %) during 14 days of storage at room temperature, thereby extending shelf-life and maintaining fruit quality. This research establishes a robust platform for creating advanced sustainable bioactive packaging materials, with broad implications for reducing food waste and environmental impact.