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

•Development of a new UV-shielded films based on nanorod zinc oxide and gelatin.•Nanorod zinc oxide increased viscosity of gelatin solutions.•5% of nanorod zinc oxide decreased permeability to water by one fifth.•Nanorod zinc oxide decreased hydrophobicity and moisture contents of 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.