Hydroxypropyl methylcellulose-TiO 2 and gelatin-TiO 2 nanocomposite films: Physicochemical and structural properties.

Photocatalytic properties of titanium dioxide (TiO) have been widely studied. However, its tendency to aggregation in biopolymer-based nanocomposites limits its application for food packaging and has been few studied. The aim of this work was to study the dispersion of TiO (0-2 wt%) incorporated in the hydroxypropyl methylcellulose (HPMC-TiO) and gelatin (gelatin-TiO) film forming solutions. Particle size and zeta potential of TiO nanoparticles were investigated. Nanocomposite films were characterized as to the thickness, moisture content, solubility, color, absorption to the light, relative opacity, morphology, chemical composition, crystallinity, thermal and mechanical properties and water vapor permeability (WVP). TiO nanoparticles showed better dispersion in acid medium than water. Moisture content, water solubility and WVP of the gelatin-TiO films were influenced by the incorporation of TiO, while HPMC-TiO films were not. The increase of relative opacity of the films as TiO was more attenuated for the gelatin-TiO films due to lower TiO aggregation in gelatin. Morphology, chemical composition, crystallinity and thermal properties of the films evidenced that TiO was better dispersed in both matrices at 1 wt%. It was also concluded that TiO aggregation generated more biphasic regions in HPMC than generated in gelatin, which caused a microstructural reorganization in the matrices.