Chitosan-polyvinyl alcohol hydrogel films containing polyphenols-encapsulated ZIF-8 for pH-responsive freshness monitoring and preservation of pork.

Abstract

We developed a biodegradable hydrogel-based packaging film from chitosan and polyvinyl alcohol. The film was integrated with epigallocatechin gallate, curcumin, or anthocyanins encapsulated in zeolitic imidazolate framework-8. Due to the synergistic effects between ZIF-8 and polyphenols, the films had enhanced mechanical strength, thermal stability, and barrier properties against water vapor and oxygen. The films also exhibited antibacterial and antioxidant activities and could inhibit microbial growth and lipid/protein oxidation in fresh pork during 9-day storage at 4 °C. Moreover, the incorporated polyphenols confer pH-responsive yellow and purple-red color change and controlled release, enabling real-time visual monitoring of pork freshness. Among all film variants, the PVA-CS-Cur@ZIF-8 had the best preservation performance. It could extend the shelf life of pork by 2-4 days and had superior biocompatibility (>85%) and soil degradability (80%). Overall, this work presents a sustainable and intelligent packaging hydrogel film that can act as a preservative material and freshness indicator.