Fabrication and Characterization of Anthocyanin/ε-Polylysine Composite Films and Their Application for Freshness Preservation of Simmered Chinese pork meatballs

This study developed active and intelligent composite packaging films using carrageenan, polyvinyl alcohol (PVA), and Rhododendron pulchrum Sweet anthocyanins (RA) as base materials, incorporating varying amounts of ε-polylysine (ε-PL) to enhance the films' antibacterial and freshness-indicating properties. This study adopted a dual-functional design strategy by integrating the antimicrobial activity of ε-PL with the intelligent pH-responsive freshness indication of anthocyanins. The physicochemical properties of the films, along with their ability to preserve stewed Chinese pork meatballs (a traditional Chinese pork dish), were extensively evaluated using techniques such as Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). A major strength of this work lies in the validation of film performance in a real cooked meat product rather than only under model conditions. The results showed that increasing ε-PL content (3 g/dL, 6 g/dL, and 9 g/dL) significantly improved the films’ elongation at break, thermal stability, hydrophobicity, UV-shielding capacity, and antibacterial activity. Meanwhile, water vapor permeability (WVP) decreased at first, then increased with higher ε-PL concentrations. Among the tested formulations, CP-RA-6 g/dL ε-PL was identified as the optimized formulation. In storage trials, this film effectively slowed weight loss, pH increase, and lipid oxidation, while also delaying microbial growth. It maintained the color and texture integrity of the meatballs and outperformed the control film in terms of TVB-N reduction. Electronic tongue and sensory evaluations confirmed that the film preserved the umami taste and overall flavor profile of the meatballs. However, further studies are needed to address the film’s stability at higher temperatures and its scalability for industrial applications. Overall, these results underscore the potential of CP-RA-6 g/dL ε-PL films for use in active and intelligent food packaging, with promising applications in extending shelf life and enhancing food quality retention.