Effect of TiO2 nanoparticles on the physico-mechanical and ultraviolet light barrier properties of fish gelatin/agar bilayer film

• Bilayer fish gelatin/agar nanocomposite film containing nano-TiO2 was developed.
• TiO2 decreased water vapor permeability of the bilayers more than 30%.
• The tensile strength of the bilayer films improved with 0.5 g/100 g nano-TiO2 addition.
• Nano-TiO2 improved the barrier properties of the films against UV light at low concentration.
• Swelling ratio and moisture content increased with the increase in the nano-TiO2 content.

Bilayer gelatin/agar films containing different concentrations of TiO2 (0.5, 1, and 2 g/100 g) were prepared by incorporation of anatase titanium dioxide nanoparticles in the fish gelatin layer of the bilayers. Gelatin/agar bilayer film was produced from the monolayers using the casting method in two steps and their microstructural, physical, mechanical and optical characteristics were studied. Results showed that the addition of TiO2 decreased water vapor permeability of the bilayers more than 30%, upon increasing TiO2 content to 2 (g/100 g). However, swelling ratio and moisture content increased with the increase in the nano-TiO2 content, probably due to the hydrophilic nature of the TiO2 nanoparticles. The tensile strength of the bilayer films increased from 10.80 to 13.91 MPa upon increasing nano-TiO2 content from 0 to 0.5 (g/100 g); however, tensile strength decreased with further increase of the nanoparticle concentration. In addition, the metallic nature of nano-TiO2 considerably improved the barrier properties of the bilayer films against UV light at low concentration, while it increased their opacity. This property might help in the preservation of light-sensitive foods, but more studies on real food systems are required.