Development of carboxymethyl cellulose/starch films enriched with ZnO-NPs and anthocyanins for antimicrobial and pH-indicating food packaging

Active packaging, which can monitor food freshness and extend the shelf life, has gained significant attention in recent years. This study aims to develop a novel carboxymethyl cellulose (CMC)/starch/anthocyanins/ZnO active films with enhanced properties and specific functionalities. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) revealed that the addition of anthocyanins and nano-ZnO particles (ZnO-NPs) led to heterogeneous microstructures and a slight decrease in the crystallinity. Fourier transform infrared spectroscopy (FTIR) indicated that there were no chemical interactions among film components. Active films containing ZnO-NPs exhibited improved ductility, as well as enhanced light barrier and water resistance properties. Notably, a shift from hydrophilic to hydrophobic behavior of the films was observed with high ZnO-NP content, as evidenced by a significant increase in the water contact angle (from 63.44° to 114.22°). Furthermore, the presence of only 1 % ZnO-NPs resulted in efficient inhibition of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) growth. Moreover, active films containing both anthocyanins and ZnO-NPs were highly sensitive to pH changes in buffer solutions (pH 2-11). Based on the results, a recommended film formulation for future active packaging applications is a 80:20 CMC/starch blend with 3 % ZnO-NPs and 0.1 g anthocyanins.