Abstract: In this experiment, antimicrobial composite films were prepared from soy protein isolate (SPI) surface-modified nano-TiO2. The formulation was optimized using one-factor-at-a-time and orthogonal array design methods. Tensile strength (TS), breaking at break (EAB), water vapor permeability (WVP), light permeability, oxygen permeability and carbon dioxide permeability were used as response variables. Results showed that the optimum combination was determined as 4.5 g/100 mL of SPI, 2.0 g/100 mL of modified nano-TiO2 and 1.5 g/100 mL of glycerol. The contact angle of the formed film was 115.3°. Fourier transform infrared spectroscopy (FTIR) revealed that the spectral patterns of modified nano-TiO2/SPI composite films, nano-TiO2/SPI composite films and ordinary SPI films were similar in the range of 4 000-600 cm-1. The results of scanning electron microscope (SEM) and atomic force microscope (AFM) consistently showed that compared with nano-TiO2/SPI composite films and ordinary SPI films, the surfaces of modified nano-TiO2/SPI composite films were more compact and flatter and the surface performance was better; furthermore, the structural property was also improved. After being exposed to UV light at 365 nm for 6 h, the strongest bacteriostatic activity of the films containing 2 g/100 mL of modified nano-TiO2 against Escherichia coli and Listeria monocytogenes were observed with 91.14% and 92.81% inhibition, respectively. Owing to its good mechanical properties and antibacterial activity, nano-TiO2/SPI antimicrobial film has huge potential for application in food packaging.

Key words: nano-TiO2, surface modification, soy protein isolate, antimicrobial film, photocatalysis