A dual-pH-responsive smart starch film with antibacterial and controlled-release functions constructed from tannic acid‑copper nanoparticles for strawberry preservation.

Polysaccharide-based films offer considerable potential for food shelf life, but are still limited by their antibacterial activity and poor physical properties. However, current improvement approaches often struggle to achieve a balance among multiple physical properties of films and the controlled release of antibacterial agents, and may also introduce potential biotoxicity. Herein, we developed a biocompatible controlled-release system by incorporating copper-tannic acid nanoparticles (Cu@TA NPs) into starch films. The Cu@TA NPs exhibited excellent compatibility and could be uniformly dispersed in the starch matrix. Compared with the pure starch films, composite films obviously improved mechanical strength (9.40 MPa), hydrophobicity, and water vapor barrier performance (2.22 × 10-12 g·cm·cm-2·s-1·Pa-1). Meanwhile, they exhibit excellent UV resistance and antioxidant properties, with DPPH radical scavenging capacity and total antioxidant capacity values that are 10.12- and 9.02-fold higher than those of pure starch films, respectively. More importantly, the pH-responsive release mechanism enables starch films to sense changes in the microenvironment, thereby achieving targeted antibacterial effects and markedly prolonging the shelf life of strawberries. Moreover, composite films exhibit high biocompatibility and environmental friendliness. Overall, this study provides a promising approach for developing smart, efficient, and low-toxicity packaging materials with controlled-release and antibacterial functions, offering significant potential for food preservation applications.