Hydroxypropyl methylcellulose-TiO₂ and gelatin-TiO₂ nanocomposite films: Physicochemical and structural properties

Photocatalytic properties of titanium dioxide (TiO₂) 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 TiO₂ (0-2 wt%) incorporated in the hydroxypropyl methylcellulose (HPMC-TiO₂) and gelatin (gelatin-TiO₂) film forming solutions. Particle size and zeta potential of TiO₂ 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). TiO₂ nanoparticles showed better dispersion in acid medium than water. Moisture content, water solubility and WVP of the gelatin-TiO₂ films were influenced by the incorporation of TiO₂, while HPMC-TiO₂ films were not. The increase of relative opacity of the films as TiO₂ was more attenuated for the gelatin-TiO₂ films due to lower TiO₂ aggregation in gelatin. Morphology, chemical composition, crystallinity and thermal properties of the films evidenced that TiO₂ was better dispersed in both matrices at 1 wt%. It was also concluded that TiO₂ aggregation generated more biphasic regions in HPMC than generated in gelatin, which caused a microstructural reorganization in the matrices.