A novel pH-responsive corn starch/polylactic acid bilayer film: Application for the freshness preservation of hairtail (Trichiurus haumela)

Food packaging is essential for preventing contamination, but traditional plastics contribute significantly to pollution, highlighting the need for sustainable alternatives. Intelligent packaging can extend food shelf life by monitoring factors like pH, temperature, and humidity. Hairtail ( Trichiurus haumela ) is highly perishable, necessitating advanced preservation technologies. A bilayer composite film (ZnO-MAE/CS/PLA) was developed using corn starch (CS) and polylactic acid (PLA) via casting. The CS inner layer is hydrophilic, and the PLA outer layer is hydrophobic. Mulberry anthocyanin extract (MAE) and zinc oxide nanoparticles (ZnO NPs) provide antioxidant, antimicrobial, and pH-responsive properties. Unlike petroleum-based dyes, MAE is non-toxic and eco-friendly. SEM analysis showed uniform ZnO NP dispersion at 2-4%, improving tensile strength (8.08 to 9.58 MPa) and elongation (24.71% to 25.56%). Higher concentrations led to aggregation and slight reductions in mechanical properties. Optimal performance, with balanced mechanical strength, antimicrobial activity against Escherichia coli and Staphylococcus aureus , and pH sensitivity, was observed at 6% ZnO NPs. The film also inhibited microbial growth and nutrient oxidation, significantly extending the shelf life of hairtail. Thus, ZnO-MAE/CS/PLA films hold great potential as intelligent, eco-friendly packaging for hairtail preservation.