pH-responsive controlled-release antimicrobial active film based on gelatin/chitosan incorporated with HNT nanocomposite

Stimuli-responsive active packaging materials represent a promising frontier in food preservation by combining controlled-release functionality with environmental adaptability. Herein, a novel pH-responsive antibacterial bioactive packaging film based on a chitosan/gelatin (CS/GA) composite was developed by incorporating nanocomposites (NP) prepared through layer-by-layer assembly of natural polyelectrolytes onto modified halloysite nanotube (HNT), with carvacrol (Car) as the encapsulated active agent. The results showed that the developed composite films exhibited pH-responsive behavior under different pH conditions (4.0, 7.0, and 9.0), with a preferential release under alkaline conditions. The release rate was governed by the synergistic effects of carrier structural relaxation/dissolution within the NP, film diffusion, and structural relaxation/dissolution. In addition, hydrogen bonding and electrostatic interactions among CS, GA, and the NP improved the dispersion of the NP within the film matrix, thereby enhancing the film's mechanical strength, gas barrier performance, and thermal stability. The resulting active film effectively inhibited the growth of E. coli and S. aureus , and markedly prolonged the shelf life of pork. Overall, the developed pH-responsive active packaging films have great potential for application in future smart food preservation systems and lay a foundation for designing stimuli-responsive materials for different food environments.