Effects of ultrasonic/microwave-assisted treatment on the properties of corn distarch phosphate/corn straw cellulose films and structure characterization.

Edible films were casted using aqueous solutions of corn distarch phosphate (CDP, 3 wt%) and corn straw cellulose (CSC, 0.5 wt%). The effects of ultrasonic, microwave and ultrasonic/microwave-assisted treatment on mechanical properties and light transmittance, as well as the water vapour permeability (WVP) of edible films, were evaluated. It was found that corn distarch phosphate/corn straw cellulose (CDP/CSC) films treated using ultrasonic waves/microwaves for a certain condition has a distinct increase in tensile strength, elongation at break and light transmittance and a drastic decrease in WVP. Moreover, scanning electron microscopy demonstrated that the surface and cross-section morphology of CDP/CSC films after ultrasonic/microwave-assisted treatment were smoother, denser and without a notable phase separation compared with control films. The results of mechanical properties and barrier properties were in agreement with the changes in molecular interactions detected by Fourier transform infrared spectroscopy and X-ray diffraction analysis. These findings indicate that ultrasonic/microwave-assisted treatment can improve the application of biodegradable films.