Effects of Ultrasonication or Photocatalytic Pretreatment on Antibacterial Properties of Soy Protein/Nano-titanium dioxide Composite Films
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Abstract:
Biodegradable soy protein (BSP)-titanium dioxide nanocomposite films were fabricated using a combination of ultrasonication or photocatalytic pretreatment and a solution-casting method, and the effects of ultrasonication, photocatalytic pretreatment, and titanium dioxide content of the film on properties of the composite film were analyzed. At a low titanium dioxide concentration (<2%), the scanning electron microscopy (SEM) results showed that the titanium dioxide nanoparticles were evenly dispersed in the protein matrix, so that the swelling-induced deformation of the film was reduced, and the mechanical properties, thermal stability, and antibacterial activity of the composite film were improved. The data on intrinsic fluorescence spectra, Fourier transform infrared spectra (FT-IR), and X-ray diffraction (XRD) confirmed that the interaction between protein and nanoparticles was mainly mediated by hydrogen bonding, and that the photocatalytic pretreatment further strengthened the cross-linking between protein molecules and nanoparticles, thus the mechanical properties, thermal stability, and antibacterial activity of the composite films prepared by photocatalytic pretreatment were improved as compared with those of the films prepared by ultrasonication. Nevertheless, a high titanium dioxide concentration (>2%) promoted self-assembly of titanium dioxide-titanium dioxide nanoparticles, leading to fluorescence quenching, worsening of mechanical properties, and an increase in swelling-induced deformation. Soy protein/nano- titanium dioxide composite films prepared by photocatalytic pretreatment may potentially become new green packaging materials with antibacterial properties.
