Physico-Mechanical Characterization and Antimicrobial Properties of Fish Protein Isolate/Fish Skin Gelatin-Zinc Oxide (ZnO) Nanocomposite Films

Antimicrobial nanocomposite films based on fish protein isolate (FPI)/fish skin gelatin (FSG) (1/1 w/w) prepared at pH 3 and 11 containing zinc oxide nanoparticles (ZnONP) at different levels (0–4 % w/w of protein) were characterised. At both pH 3 and pH 11, tensile strength (TS) increased, whilst elongation at break (EAB) and water vapour permeability (WVP) decreased as ZnONP content increased (p < 0.05). FPI/FSG-ZnO nanocomposite films had lower transparency, b*-values (yellowness), and ∆E*-values (total colour difference) than the control FPI/FSG film (p < 0.05). Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopic analysis revealed that there was interaction between ZnONP and protein in the film matrix. Based on thermogravimetric analysis, ZnONP could improve the thermal stability of the nanocomposite films. X-ray diffraction (XRD) analysis confirmed the crystalline structure of the ZnONP in the nanocomposite films. FPI/FSG-ZnO nanocomposite films, especially those prepared at pH 3, exhibited strong antibacterial activity and thus could be used as an active food packaging material.