A pH-responsive bilayer film based on PHBV/ZnO and polyvinyl alcohol/carboxymethyl konjac glucomannan/alizarin was developed for monitoring and maintaining pork freshness.

A PAC@PHZ-II bilayer film composed of polyvinyl alcohol/carboxymethyl konjac glucomannan/alizarin as the sensor layer and poly(3-hydroxybutyrate-co-3-hydroxyvaleric acid)/nano-ZnO as the antibacterial layer was developed using electrospinning technology for meat preservation and freshness perception. Structure analyses revealed that there are interactions between the sensor layer and antibacterial layer. The bilayer film has a lowest water vapor transmission rate of 26.03 ± 0.21 g·m-2·h-1, and the tensile strength and elongation at break are approximately 150% and 290% higher than those of single-layer films, respectively. The bilayer film is sensitive to pH and ammonia, exhibiting visible color changes from yellow to purple. Antibacterial test indicated the dual functional film had strong antibacterial activity against Staphylococcus aureus, Escherichia coli and Listeria monocytogenes. Pork packaged with the film exhibits a 3 days shelf-life extension, and the color changed when meat freshness decreases, suggesting a potential use in preserving and monitoring pork freshness.