The effect of nanoreinforcement geometry on the physical and structural properties of whey protein concentrate/omega-3 rich oil/TiO2 nanocomposite films†

Abstract

Whey protein concentrate (WPC)/omega-3 rich oil/TiO₂ nanocomposite films were prepared by casting as a bio-based alternative to petroleum-based plastics. The effect of adding Tween 20 and/or TiO₂ nanoreinforcement in two geometries, spheres or nanotubes (NTs), on the physical properties and structure was investigated. The initial emulsions were monomodal systems, where the maximum value of the main peak decreased with the addition of Tween 20. The addition of Tween 20 also increased the transparency of the films, while the presence of TiO₂ reinforcement helped block light, with nanotubes having less effect in the visible range compared to nanospheres. In comparison to the control, the Young's modulus (E) increased with the addition of spherical TiO₂ nanoparticles at a concentration of 0.2% when the formulation included Tween 20. The addition of nanotubes at 0.1% and 0.2% also enhanced the tensile and mechanical properties. The film containing 0.2% nanotubes exhibited the highest E, storage (E′), and loss (E′′) moduli, along with the shortest elongation at break (ε_b) among all the films. Structural analyses using SEM, EDS, and SAXS revealed that TiO₂ nanospheres were prominent on the surface, particularly at the bottom of the film, while nanotubes were integrated into the bulk region of the film, forming part of the matrix. The structural description provided in this manuscript allows for the conclusion that the enhanced physical properties of nanotube-reinforced films were due to their distribution within the film matrix, which was dependent on geometry. The film reinforced with 0.2% nanotubes demonstrated potential for food packaging.