The effects of ultrasonic/microwave assisted treatment on the properties of soy protein isolate/titanium dioxide films

- Soy protein isolate/titanium dioxide (SPI/TiO2) films were prepared.
- TiO2 nanoparticles improved SPI-based films' properties.
- Ultrasonic/microwave assisted treatment improved films' properties.
- GAB and Henderson models fit best with films sorption isotherms.

Soy protein isolate (SPI, 5.0 g/100 mL,) films embedded with nano-TiO2 (0, 0.5, 1.0, 1.5 and 2.0 g/100 mL) were prepared by solution casting and modified by ultrasonic/microwave assisted treatment (UMAT). The effects of nano-TiO2 content and UMAT time on the films' physical properties and structure were investigated. Incorporation of nano-TiO2 significantly enhanced films' mechanical properties and barrier properties, because of the intermolecular force between nano-TiO2 and SPI. UMAT time ≤20 min obviously improved films' tensile strength values (15.77 MPa, 245% higher than the control), and reduced water vapor permeability (1.8457 × 10−11 g cm−1 s−1 Pa−1, 72.11% lower than the control) and oxygen permeability values (0.8897 × 10−5 cm3 m−2 d−1 Pa−1, 57.66% lower than the control). SEM images also revealed a more compact and dense structure of films when UMAT time ≤20 min. Films' water adsorption properties were evaluated. GAB and Henderson models exhibited the best to fit experimental data, thus it was predicted that films (1.5 g nano-TiO2/100 ml) could be stable at low moisture content (0.27 kg of water/kg dry mass).