Electrospun polyvinyl alcohol/chitosan-ZIF-8@cyanidin cation-gallic acid multifunctional nanofilm for real-time visual monitoring of beef freshness

Abstract

In complex food systems, single-functional films often struggle to simultaneously achieve effective freshness indication and preservation. This study developed a pH-responsive multifunctional film using an integrated “stable indicator–antibacterial–antioxidant–indication” strategy. First, unstable cyanidin cation (CC) was loaded into zeolitic imidazolate framework-8 (ZIF-8). Then, ZIF-8-loaded CC (ZIF-8@CC) was combined with gallic acid (GA) and incorporated into a polyvinyl alcohol (PVA) and chitosan (CS) matrix via electrospinning. The multifunctional film was characterized for its morphology, pH response, antibacterial and antioxidant properties, and biocompatibility, then applied in beef preservation. The results showed that the incorporation of CS and ZIF-8@CC significantly improved the hydrophobicity and mechanical strength of the film. The film exhibited broad-spectrum pH-responsive behavior, with color gradually changing from pink to brown within the pH range of 1–12, and high sensitivity toward NH₃·H₂O, along with good color stability. Antibacterial tests demonstrated an inhibition rate of over 95% against common foodborne pathogens, and whole-genome transcriptome analysis revealed the synergistic antibacterial mechanism among ZIF-8/Zn²⁺, CS, and GA. Meanwhile, the film also exhibited excellent antioxidant performance, with a free radical scavenging rate exceeding 86%. When applied in beef preservation, the film not only visually indicated the spoilage process through color changes but also extended the shelf life by 3–4 days. Furthermore, by integrating smartphone RGB analysis technology, real-time and quantitative monitoring of beef freshness was achieved. This study provides a new strategy for developing multifunctional films for intelligent packaging, with potential applications in quality monitoring of fresh foods.