Optimized UV-barrier carboxymethyl cellulose-based edible coatings reinforced with green synthesized ZnO-NPs for food packaging applications

Abstract

The widespread use of sodium carboxymethyl cellulose (CMC) in the production of edible coatings is returned to its biodegradable, biocompatible, and non-toxic nature. However, neat CMC edible coatings lack UV-shielding activity and have poor antimicrobial properties. This study aimed to develop a CMC-based coating with optimal UV-barrier properties by incorporating aloe vera (AV) and green synthesized zinc oxide nanoparticles (ZnO-NPs). The composition and synergistic effects of CMC, AV, and ZnO-NPs were optimized using central composite design to achieve the best UV-barrier properties. When using the optimized compositions of CMC (1.0 g), AV (3.0 g), and ZnO-NPs (5.0 wt%), the minimum UV-transmittance achieved was 4.75%. Fourier transform infra-red and wide-angle X-ray diffraction were used to confirm the interactions between the coating components. The incorporation of ZnO-NPs into CMC/AV was validated through surface morphology analysis via scanning electron microscopy and by examining the distribution of ZnO-NPs using transmission electron microscopy. CMC/AV/ZnO-NPs coatings showed excellent water barrier, mechanical, thermal, and antimicrobial properties when compared with the neat carboxymethyl cellulose coating. In addition, CMC/AV/ZnO-NPs coatings significantly resisted both mass loss and spoilage of green capsicum for a 15-day storage period. These results proved that the optimized coating could replace the plastic packaging candidates and be used potentially to preserve food products.