Effect of nano-TiO2 particle size on the performance of chitosan/zein/red radish anthocyanin composite film for visual monitoring of mushroom freshness

The effect of nanoscale titanium dioxide (nano-TiO2) particle size on the performance of chitosan/zein (C/Z) film loaded with red radish anthocyanin (RRA) was studied. The microstructure and spectral characteristic of films were evaluated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). Results demonstrated that the smaller the size of nano-TiO2, the stronger the interaction with the film matrix, the tighter the network structure formed, and the smaller the existing aggregates. Incorporation of nano-TiO2 improved the thermal stability, photostability, hydrophobicity and UV-Vis light barrier properties of films. However, the mechanical properties and swelling degree of films had been reduced to a noticeable extent. Moreover, the nanocomposite films exhibited excellent sensitivity to pH, and the color values of C/Z/R-25 nm and C/Z/R-100 nm films displayed a high correlation with the freshness of mushroom. These results were significant to enhance the stability of anthocyanin and prepare high-performance bio-based composite films for visual monitoring of food.