Development and evaluation of soybean protein isolate–based antibacterial nanocomposite films containing nano-TiO2

Designing soy protein isolate (SPI)-based composite films with great antibacterial properties and high ultraviolet (UV)-shielding remains an intractable challenge. This study aimed to blend nano-TiO2 particles (1%−4% w/w SPI) with soybean protein isolate (SPI) to form a composite film using the casting method to improve the properties of the SPI-based film. Dynamic light scattering showed that nano-TiO2 was well-embedded in the SPI in the film solution. Scanning electron microscopy, x-ray diffraction and fourier-transform infrared spectroscopy also revealed a strong intermolecular interaction between nano-TiO2 and SPI. Further, nano-TiO2 (3% w/w SPI) composite had obviously enhanced color and ultraviolet-shielding properties compared with the SPI film. Is hydrophobicity contact angle was two times that of SPI film, the tensile strength increased twofold, and the water vapor permeability was one-third of the SPI film. Additionally, the bacteriostatic effects of nano-TiO2 on Escherichia coli (E. coli) and Bacillus cereus (B. cereus) were concentration- and time-dependent. Collectively, an appropriate increase in the nano-TiO2 content (3%) significantly improved the properties and promisingly extended the shelf life of SPI-based films prone to microbial spoilage, suggesting its potential application in the packaging industry.