A CMCS/TA-Fe hydrogel film based on metal-phenolic network coordination for intelligent preservation of cooked meat

Ready-to-eat cooked meat products contain high levels of moisture and nutrients, making them highly vulnerable to microbial contamination and subsequent quality degradation during storage. Therefore, the development of green packaging materials that integrate active preservation functions with freshness indication is of great significance. In this work, a carboxymethyl chitosan (CMCS)/tannic acid (TA)-Fe 3+ coordination hydrogel (CMCS/TA-Fe) film with favorable biocompatibility and degradability was fabricated through a facile coordination-driven self-assembly strategy, leveraging the multiple interactions among CMCS, TA, and ferric ions (Fe 3+ ). The introduction of the TA-Fe 3+ metal-polyphenol markedly enhanced the mechanical performance of the film, increasing its storage modulus (G′) to approximately 2.4 × 10 4  Pa, and endowed it with efficient photothermal conversion capability. Under near-infrared irradiation at 808 nm, the film surface temperature rapidly increased to 103 °C within 15 min, enabling complete inactivation of Escherichia coli and Staphylococcus aureus . In addition, the dynamic coordination structure of TA-Fe 3+ exhibited pH-responsive chromatic behavior in a model system, resulting in distinct and reversible color changes under different pH conditions. These color variations suggest the potential of the CMCS/TA-Fe film as a visual indicator for freshness-related pH changes. When applied to the refrigerated preservation of cooked chicken breast, the CMCS/TA-Fe film combined with near-infrared irradiation effectively inhibited microbial proliferation, delayed pH increase, reduced moisture loss, and preserved textural and sensory quality. Overall, this study demonstrates a multifunctional and environmentally friendly hydrogel film that integrates photothermal antibacterial activity with a pH-responsive color indication function, offering a promising strategy for intelligent food packaging applications.