Enhancing the UV-Light Barrier, Thermal Stability, Tensile Strength, and Antimicrobial Properties of Rice Starch-Gelatin Composite Films through the Incorporation of Zinc Oxide Nanoparticles.

The effects of zinc oxide nanoparticles (ZnONPs) on the properties of rice starch-gelatin (RS-G) films were investigated. ZnONPs were synthesized by a green method utilizing Asiatic pennywort ( Centella asiatica L.) extract. The ZnONPs were rod-shaped, with sizes ranging from 100-300 nm. An increase in the concentration of ZnONPs significantly ( p < 0.05) increased the thickness (0.050-0.070 mm), tensile strength (3.49-4.63 MPa), water vapor permeability (5.52-7.45 × 10 -11 g m/m 2 s Pa), and thermal stability of the RS-G-ZnONPs nanocomposite films. On the other hand, elongation at break (92.20-37.68%) and film solubility (67.84-30.36%) were significantly lower ( p < 0.05) than that of the control RS-G film (0% ZnONPs). Moreover, the addition of ZnONPs strongly affected the film appearance, color, transmission, and transparency. The ZnONPs had a profound effect on the UV-light barrier improvement of the RS-G film. The crystalline structure of the ZnONPs was observed in the fabricated nanocomposite films using X-ray diffraction analysis. Furthermore, the RS-G-ZnONPs nanocomposite films exhibited strong antimicrobial activity against all tested bacterial strains ( Staphylococcus aureus TISTR 746, Bacillus cereus TISTR 687, Escherichia coli TISTR 527, Salmonella Typhimurium TISTR 1470) and antifungal activity toward Aspergillus niger . According to these findings, RS-G-ZnONPs nanocomposite film possesses a potential application as an active packaging: antimicrobial or UV protective.