Development and characterization of multifunctional fish gelatin composite films reinforced with ε-polylysine and zinc oxide nanoparticles

Active compounds were usually incorporated into biopolymer films to enhance their properties. The tensile strength (TS) and elongation at break (EAB) of the gelatin composite films increased along with the addition of ε-polylysine (ε-PL) and zinc oxide nanoparticles (nano-ZnO). When the concentrations of ε-PL and nano-ZnO were 4% and 0.5%, TS and EAB reached to the maximum which were 53.98 ± 2.61 MPa and 16.05 ± 1.76%. The water vapor permeability, water solubility, and water content of the composite films decreased from 2.01 ± 0.04 10⁻¹⁰ g m⁻¹Pa⁻¹ s⁻¹ to 1.56 ± 0.07 × 10⁻¹⁰g m⁻¹ Pa⁻¹ s⁻¹, from 45.23 ± 1.54% to 31.39 ± 1.24% and from 23.89 ± 1.41% to 17.34 ± 2.61%, respectively, compared with gelatin film. The light barrier capacity of the composite film was improved. The surface of the film was relatively smooth, and the cross-section was overall flat. FTIR results indicated that no chemical reaction occurred among ε-PL, nano-ZnO and gelatin. The chemical structure of the films remained unchanged throughout the heat-sealing process. Moreover, the gelatin films containing ε-PL and nano-ZnO showed excellent antibacterial activity. Our findings suggest that the gelatin composite films with antibacterial property hold promise for the application in food packaging materials.