Curcumin-based antibacterial waterborne polyurethane/gelatin composite film for pork preservation and freshness indication

Gelatin possesses excellent film-forming ability, biodegradability, and biocompatibility, which makes it a promising alternative to petroleum-based plastics. However, its application in food packaging is limited by its brittleness, high water sensitivity, and insufficient microbial protection. In this study, curcumin was introduced as a chain extender into castor oil-based waterborne polyurethane (CWU), which was then blended with gelatin as a functional material to create reactive food composite films (CWGL). The effects of varying CWU concentrations on the microstructure and properties of the films were thoroughly investigated. The incorporation of CWU enhanced the mechanical properties, water solubility, water vapor barrier, oxygen barrier, and UV shielding capabilities of the gelatin-based composite films. Additionally, CWU imparted antioxidant, antibacterial, and pH-responsive properties to the CWGL. Packaging application tests demonstrated that CWGL could extend the shelf life of fresh pork up to 10 days under refrigeration. Furthermore, CWGL exhibited a visible color change (∆E > 5) during pork storage, suggesting its potential use as a freshness-indicating innovative packaging. This study presents a novel strategy to advance the application of gelatin in innovative food packaging.