Intelligent bilayer films based on polyvinyl alcohol/carboxymethyl cellulose-chitosan for efficient preservation and...

This study developed a bilayer film integrating preservation and freshness-indicating capabilities to address the quality deterioration of beef during storage and transportation. The inner protective layer was fabricated using polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), and a Pickering emulsion (PE) loaded with oregano essential oil (OEO). This layer conferred the film with predominant antioxidant activity (ABTS radical scavenging rate > 89%) and potent antibacterial activity (inhibition rates of 96.91% against Escherichia coli and 91.23% against Staphylococcus aureus), thus achieving effective preservation. The outer indicator layer consisted of chitosan (CS) and alizarin (AL), which endowed the film with high sensitivity to pH and ammonia, thereby providing real-time visual indication of beef freshness through distinct color transitions. Structural analysis indicated that the film was stabilized through synergistic interactions of ester bonds, amide bonds, and hydrogen bonds. These interactions not only consumed the hydrophilic groups within the backbone but also facilitated the formation of a dense crosslinked network, significantly enhancing the barrier properties and mechanical strength of the film. Beef preservation tests confirmed that the film prolonged the shelf life of beef to 15 days while enabling visual freshness indication. Furthermore, a GhostNet model was employed to correlate the freshness status of beef with the color of the film, achieving an accuracy of 97.08% in identifying beef quality. Overall, this study provides a feasible strategy for developing intelligent packaging systems that combine efficient preservation with real-time freshness indication for meat products.