Comparison of nano-zinc oxide or calcium chloride incorporated polyvinyl alcohol/chitosan/anthocyanin films for active and intelligent packaging

Polyvinyl alcohol (PVA) and chitosan (CS) were mixed with purple tomato anthocyanins (PTA), and then nano zinc oxide (nano-ZnO) or calcium chloride (CaCl₂) were added to prepare PVA/CS/PTA/ nano-ZnO (PCP-ZnO) or PVA/CS/PTA/CaCl₂ (PCP-CaCl₂) films. The effects of nano-ZnO and CaCl₂ on the morphology, pH response, color stability, color reversibility, antibacterial activity, antioxidant activity, mechanical properties, water vapor permeability and UV absorption characteristics of films were studied. In addition, its application in intelligent packaging to monitor the freshness of pork was also studied. It was found that both nano-ZnO and CaCl₂ can reduce the transmittance of the film in the visible light region, and the film with addition of nano-ZnO was more sensitive to pH. During the 14 day storage period, the film modified with CaCl₂ exhibited better color stability. SEM images indicate that the addition of nano-ZnO or CaCl₂ alters the microstructure of the film. The mechanical, antibacterial and antioxidant properties and also the application as freshness indicator of PCP-CaCl₂ film were superior to those of PCP-ZnO film. Those indicated that the prepared PCP-CaCl₂ film is a potential candidate for active and intelligent packaging applications.

Graphical abstract