Physical and structural characterization of edible bilayer films made with zein and corn-wheat starch

Edible bilayer films prepared using an additional of zein (Z) layer casted on the corn-wheat (CW) starch films were prepared and characterized in terms of colour, thickness, water content, optical, water vapour permeability (WVP), mechanical properties and antioxidative capacity. Results showed that the colour, thickness, water content, elongation at break (E), and antioxidative capacity increased with the increasing of zein addition, but WVP and tensile strength (TS) decreased. In comparison with biaxially oriented polypropylene polyethylene composite films (BOPP-PE), CW10/Z3 and CW8/Z3 even showed better antioxidative capacity and elongation at break (E). The surface and cross-section micrographs were imaged by scanning electron microscopy (SEM) and atomic force microscopy (AFM). On both of SEM and AFM images, CW10/Z1 and CW10/Z2 films exhibited smoother surface and more compacted structure than other films. Besides, CW10/Z3 and CW8/Z3 of SEM images showed the better cross-section. Therefore, CW/Z edible bilayer films could be potentially used as a new inner package material for oil bag in instant food to improve the development of food industry. Keywords: Bilayer films, Corn-wheat starch, Zein, Antioxidative capacity, Surface and cross-sectional morphology