Fabrication of ZnO Nanoparticles Using the Top‐Down Method and Its Effect on the Rheological Properties of Gelatin‐Based Bionanocomposite Solutions and Films

ABSTRACT Gelatin is a thermoplastic biopolymer with excellent film‐forming properties that make it suitable for food packaging applications. However, gelatin films still have limitations owing to their high water vapor transmission rate (WVTR) and limited flexibility. Incorporating ZnO nanoparticles (ZnO‐NPs) into gelatin films is expected to improve the water vapor barrier and enhance the flexibility without significantly changing the rheological properties of the composite solution. This study aimed to determine the impact of adding ZnO‐NPs on the rheological properties of a nanocomposite solution and the mechanical properties of the resulting gelatin film. ZnO‐NPs were successfully fabricated using a top‐down approach, with the smallest particle size achieved through a combination of calcination at 100°C for 3 h, ultrasonication at 70% power for 1 h, and the addition of 0.1% w/v gelatin as a capping agent. Gelatin‐based composite solutions containing the smallest particle size of ZnO‐NPs at concentrations of 0%, 1.25%, and 2.50% w/w were prepared and cast into films. Rheological analysis showed dilatant (shear‐thickening) behavior, and the addition of ZnO‐NPs had no significant effects on the rheological parameters, indicating that the addition of ZnO‐NPs at concentrations of up to 2.50% w/w did not alter the flow properties of the composite solutions. The gelatin films were rigid and slightly yellow. Increasing the amount of ZnO‐NPs reduced the tensile strength and Young's modulus, while the elongation at break peaked at 1.25% w/w. A reduction in the WVTR was observed, which is advantageous because it improves the moisture barrier properties of bioplastics, thereby enhancing food preservation.