Zinc Oxide Nanoparticle Synthesis, Characterization, and Their Effect on Mechanical, Barrier, and Optical Properties of HPMC-Based Edible Film

Abstract

Zinc oxide nanoparticles (ZnO NPs) have been explored for controlling food spoilage microorganism. ZnO NPs were prepared by wet chemical synthesis using zinc nitrate as a precursor and sodium hydroxide as reducing agent. Nanorods and hexagonal plate shape ZnO NPs were obtained for different reaction time of 2 h and 24 h, respectively. Effect of hydroxypropyl methylcellulose (HPMC) as capping material on the morphology, size distribution, and optical properties of ZnO nanoparticles was studied by FESEM, TEM, DLS, UV-visible spectroscopy, and XRD analyses. Results showed that HPMC as capping material prevent the agglomeration of nanoparticles during synthesis and maintained uniformity in ZnO NPs size. Strong antimicrobial activity of prepared ZnO NPs was observed and minimum inhibitory concentration (MIC) for food application was determined. MIC for Staphylococcus aureus was 0.5 mg/ml. For Penicillium expansum 1 mg/ml showed approximately 80% inhibition and 2 mg/ml concentration showed 95% inhibition at the twelfth day for all ZnO NPs. HPMC-ZnO bio-nanocomposite films, prepared by incorporating capped ZnO NPs in HPMC biopolymer, showed improved mechanical and barrier properties and decreased transparency of film. Results showed that capped ZnO NPs obtained from 24 h reaction time were more effective in improving the barrier properties of HPMC film.