Abstract: The thermal properties and microstructure of five edible composite films (CW10/Z0, CW10/Z1, CW10/Z2, CW10/Z3 and CW8/Z3) consisting of two layers: corn and wheat starch layer and zein layer were evaluated by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), different scanning calorimetry (DSC), X-ray diffraction (X-RD) and Fourier transform infrared (FTIR) spectroscopy and the differences in the physicochemical properties of these composite films were also studied. The results showed that after adding a layer of zein, the water resistance was enhanced and the mechanical properties were improved. Meanwhile, tightly coupled bilayer films were observed by SEM. TG and DSC analysis showed that the thermal stability of the bilayer films was improved. X-RD indicated good compatibility between the biological macromolecules, and FTIR spectroscopy revealed that new hydrogen bonds were formed between the two film layers. The results of this study can provide an important basis for the application of corn and wheat starch/zein bilayer films in food packaging.

Key words: bilayer films, corn and wheat starch, zein, thermal properties, microscopic properties