The Antibacterial and pH Responsive Dual-Function (Sc2O3-MgO)/Alizarin/Polycaprolactone/Polyvinylpyrrolidone Nanofiber Membranes for Fresh Shrimp Packaging

The aim of our research reported in this paper was to develop electrospun (Sc2O3-MgO)/alizarin/polycaprolactone/polyvinylpyrrolidone nanofiber membranes with pH-responsive and antibacterial properties. Scanning electron microscopy results showed that alizarin (ALI) was uniformly distributed in the polycaprolactone/polyvinylpyrrolidone (PCL/PVP) matrix, forming pH-responsive membranes. The X-ray diffractometer (XRD), attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) and thermal analysis results demonstrated that both ALI and Sc2O3-MgO loadings were effective. Moreover, the addition of 0.16 wt% ALI induced distinct color changes (from pale yellow to purple, pH = 2-12) in the ALI/PCL/PVP nanofiber membranes. This behavior stemmed from the hydroxyl group in ALI forming an intramolecular hydrogen bond with the carbonyl oxygen, enabling proton transfer. Furthermore, the ALI/PCL/PVP membranes containing 2.00 wt% Sc2O3-MgO showed good antibacterial effect against Escherichia coli (E. coli) within 24 h, of what indicating its strong antibacterial activity. In addition, a comprehensive 8-day analysis was conducted on the pH, total volatile basic nitrogen (TVB-N) and total number of live bacteria colonies of the shrimp, as well as the color changes in the film. The experiment proved that the shrimp not covered by the film became highly spoiled on the 4th day, while the shrimp covered with the SAPP-2-3 nanofiber membranes only reached a state of high spoilage on the 6th day. Therefore, the SAPP-2-3 nanofiber membranes can effectively extend the shelf life of the shrimp by 2 days. We believe this study provides a new strategy for the research of multifunctional smart food packaging films.