Effects of nanorod-rich ZnO on rheological,sorption isotherm,and physicochemical properties of bovine gelatin films

The effects of nanorod-rich zinc oxide (ZnO–nr) on the flow properties of bovine gelatin solution and on the sorption isotherm, antimicrobial, and physchochemical properties of gelatin films were investigated. ZnO–nr was incorporated into gelatin solutions at different concentrations (0.01, 0.02, 0.03, and 0.05 g/g dried gelatin). The introduction of low ZnO–nr concentrations (0.05 g/g dried gelatin) to gelatin solutions significantly increased the viscosity of the solution from 9 to 11.9 mPa s and decreased the permeability of the films to water vapor from 8.9 × 10⁻¹¹ to 1.78 × 10⁻¹¹ (g m⁻¹ s⁻¹ Pa⁻¹). Solubility in water decreased from 30% to 20%, and monolayer water content of the films decreased from 0.13 to 0.10 (g water/g dried solid), whereas their contact angle increased from 45° to 85° with increasing ZnO–nr concentration from 0 to 0.05 g/g dried gelatin. The ZnO–nr gelatin films had very low UV transmittance and were able to absorb more than 50% of the near-infrared spectra. These films showed excellent antimicrobial activity against Staphylococcus aureus. These properties suggest that ZnO–nr can be potentially used as fillers in gelatin-based films for active packaging materials in the pharmaceutical and food packaging industries.