Preparation, characterization, and antimicrobial activity of gelatin/ZnO nanocomposite films

Gelatin-based zinc oxide nanoparticle (ZnO NPs) nanocomposite films were prepared using various types of ZnO NPs, which were synthesized using two different zinc salts (zinc nitrate and zinc acetate) with or without capping agent (carboxymethyl cellulose). The ZnO NPs were in various shapes and sizes ranged from 200 to 400 nm depending on the preparation method. The gelatin/ZnO NPs nanocomposite films were characterized by UV–visible spectroscopy, FE-SEM, FT-IR, thermogravimetric analysis, and XRD. The influence of different types of ZnO NPs on the morphology, crystallization behavior, thermal stability, mechanical, water vapor barrier, water contact angle, and antibacterial properties of the gelatin-based nanocomposite films were investigated. Gelatin/ZnO NPs nanocomposite films exhibited three absorption peaks around 220–230, 270–280, and 360 nm. Apparent surface color and transmittance of gelatin film was greatly influenced by the types of ZnO NPs. FTIR spectra indicated interaction between ZnO NPs and N–H groups of gelatin. XRD data demonstrated the crystalline structure of ZnO NPs with dominant (100) facet in the gelatin/ZnO NPs nanocomposite films. ZnO NPs incorporated nanocomposite films exhibited enhanced thermal stability. Moisture content, water contact angle, water vapor permeability, and elongation at break of ZnO NPs incorporated films increased, while tensile strength and modulus of elasticity decreased compared with the control gelatin film. The gelatin/ZnO NPs nanocomposite films showed profound antibacterial activity against both Gram-positive and Gram-negative foodborne pathogenic bacteria. The nanocomposite film could be applied for the food preservation by controlling foodborne pathogens.