Properties of active starch-based films incorporating a combination of Ag, ZnO and CuO nanoparticles for potential use in food packaging applications

Starch (St)-based nanocomposite films containing single or a combination of Ag, ZnO and CuO nanoparticles (NPs) were prepared by the solution casting method. Physico-mechanical and antibacterial properties of the obtained films were investigated. The results indicated that St-ZnO film had higher tensile strength than those of St/Ag and St/CuO films at 2 wt.% of each NPs. Moreover, the film containing a combination of Ag-ZnO-Cuo NPs showed a higher tensile strength and Young's modulus than those of St/Ag film. Elongation at break % of the control (pure starch) film was the highest followed by St-Ag, St-CuO, St-ZnO, and St-Ag-ZnO-CuO nanocomposite films. The results showed that St-ZnO-CuO-Ag film with 0.667 wt.% of each NPs as well as St-ZnO (3%) film had the lowest solubility in water. The ultraviolet spectroscopy revealed that the St-ZnO film had the highest UV absorbance. Microbial tests showed that St-Ag and St-CuO films had the highest antibacterial activity against E. coli and S. aureus, respectively. With increasing NPs concentration from 1 to 3 wt.% this effect was more enhanced. We found that combinatorial use of Ag/ZnO/CuO NPs in the formulation of starch-based films exhibit synergistic effect in enhancing the antimicrobial and mechanical properties of the resulting films. This would have an important impact in the development of antimicrobial films aiming to reduce the required does of individual metallic NPs.