Fabrication of a waterproof multilayer film with enhanced antioxidant and antimicrobial properties for food packaging applications

In this work, multifunctional multilayer films consisting of a corn starch/chitosan-cinnamaldehyde-zinc oxide (CST/CS-CIN-ZnO) center-layer sandwiched between polyvinyl butyral/ethyl cellulose (PVB/EC) outer layers was produced for food packaging applications. Fourier transform infrared (FT-IR) spectroscopy confirmed that ZnO and CIN were successfully introduced into the core layer of the multilayer films. ZnO nanoparticles improved the UV resistance, barrier, antioxidant and mechanical properties of the films, while CIN and ZnO imparted synergistic antimicrobial activity against Staphylococcus aureus and Escherichia coli. Scanning electron microscopy (SEM) images indicated that the PVB/EC/CST/CS-CIN-ZnO films possessed a well-defined tri-layer structure. Compared with monolayer CST/CS-CIN-ZnO films, the multilayer films not only possessed better water resistance (water contact angle of 87.88°), but also delayed release of ZnO and CIN, thereby prolonging the antibacterial and antioxidant activities of the films. The total colony count of braised pork samples stored in the multilayer films on day 12 was significantly lower than that of the control films, highlighting the potential of multilayer films in extending the shelf life of foods.