Supramolecular interaction-enhanced green active packaging films: Design and performance of Ca²⁺-crosslinked...

Given the environmental challenges caused by petroleum-based plastics, this study developed a novel green carboxymethyl chitosan (CMCS)-based active packaging composite film (CP) through a synergistic strategy of precise Ca²⁺ coordination cross-linking and small-molecule plasticizing. Based on this strategy, the CP-4.5 film (CaCl₂: 7 wt%, DL-3-phenyllactic acid (3-PLA): 4.5 wt%) exhibited exceptional mechanical properties, including high flexibility (Young's modulus: 0.747 GPa; elongation at break: 65.2 %) and high toughness (18.4 MJ m^-3). The incorporation of CaCl₂ not only occupied voids within the CP film but also increased the physical cross-linking strength and density of the polymer network. This structural reorganization impeded the diffusion of O₂ and H₂O molecules, reducing oxygen permeability by 85.9 % and water vapor permeability by 57.6 %. Additionally, 3-PLA, functioning as a broad-spectrum antibacterial agent, imparted the CP film with superior antibacterial activity. The CP film exhibited recyclability and repairability, and underwent complete biodegradation within 56 days. Overall, the synergistic effect of CaCl₂ and 3-PLA endowed the CP film with superior mechanical properties, barrier properties, antimicrobial activity, and environmental sustainability, effectively mitigating the quality deterioration of refrigerated grass carp fillets during storage, demonstrating the promising potential of the CP film for food packaging applications.