Two different fabrication method of high-hydrophobic Bi-layer indicators based on sodium alginate-polyvinyl alcohol/chitosan-zein incorporated with alizarin@ZIF-8 for beef freshness visualization.

Intelligent films are essential for real-time monitoring of food spoilage. However, the application is often limited by challenges such as hydrophilicity and color instability. In this study, two high hydrophobic bilayer indicators based on sodium alginate-polyvinyl alcohol/chitosan-zein with alizarin grafted onto ZIF-8 carrier (AL@ZIF-8) were fabricated using the casting method and electrospinning, respectively. Molecular docking simulations confirmed the successful grafting of AL@ZIF-8 onto the film substrates. The performance of films was compared and the effectiveness in monitoring freshness indicators was evaluated. The cast film had a precisely controlled thickness due to self-assembly performance, resulting in superior mechanical properties (TS = 10.64 MPa, EB = 43.764 %). In comparison, the nanofiber films demonstrated higher UV-blocking ability (ΔE < 4), faster spoilage response, and greater safety (Cell viability >80 %). Importantly, the nanofiber films exhibited higher sensitivity in monitoring beef freshness, with a color change pattern strongly correlating with spoilage (R = 0.8976).