Thermo-mechanical, rheological, structural and antimicrobial properties of bionanocomposite films based on fish skin gelatin and silver-copper nanoparticles

Abstract

The paper focuses on the development and characterization of bionanocomposite films based on fish skin gelatin (FSG) and bimetallic Ag-Cu nanoparticles (Ag-Cu NPs). Effects of Ag-Cu NPs loadings on the thermal, mechanical, rheological, structural, and antibacterial properties of the gelatin-based films were investigated. An increase in tensile strength (TS), and a decrease in elongation at break (EAB) recorded while nanocomposite (NC) films were loaded with 2% (w/w) NPs. Nevertheless, both parameters (TS and EAB) dropped drastically with further addition of NPs (p < 0.05). Oscillatory rheological data also established that 2% NPs loading improved the mechanical property of the FSG/Ag-Cu nanocomposites. The NC films showed lower transparency, yellowness, and the total color difference over the control FSG film (p < 0.05), whereas the UV barrier property improved substantially. An interaction between NPs and gelatin matrix in the film was evidenced through Fourier transform infrared (FTIR) spectroscopy. Both differential scanning calorimetric (DSC) and thermogravimetric (TGA) analyses confirmed the incorporation of NPs significantly improved the glass transition temperature (Tg), and thermal stability of the NC films. X-ray diffraction (XRD) demonstrated a change in the crystallinity of FSG films with incorporation of NPs. However, the NC films became coarse with added NPs as indicated by scanning electron microscopy (SEM) micrographs. The NC films exhibited a strong antibacterial activity against both Gram-positive and Gram-negative bacteria. Overall, the NC films could be used as an active food packaging materials for food preservation by controlling foodborne pathogens and spoilage bacteria.