Fabrication and characterization of TiO2/whey protein isolate nanocomposite film

Composite films of whey protein isolate and TiO2 are formed through three simultaneous processes, i.e., the self-assembly of protein–protein, TiO2–TiO2, and the association of protein–TiO2. All the processes could be controlled by adjusting TiO2 concentration in the blended system. The self-assembly of protein–protein molecules constituted the main network of the composite film. A low TiO2 concentration (<0.25%) dispersed the TiO2 nanoparticles in the protein matrix, reinforced the association of protein–TiO2, reduced the ability of UVC absorption, and promoted the fluorescence and tensile strength of the composite films. In contrast, a high TiO2 concentration (>0.25%) enhanced the self-assembly of TiO2–TiO2 nanoparticles, brought fluorescent quenching, and produced a decline of the tensile strength and water vapor permeability. The transmittance of the visible, UVA, and UVB lights showed a first order exponential decay relative to the TiO2 concentration.