Novel edible composite films fabricated with whey protein isolate and zein: Preparation and physicochemical property evaluation

The present study developed a novel approach by using a common solvent to fabricate edible composite films made of whey protein isolate (WPI) and zein. Three types of spray-dried powder with WPI and zein at the ratios of 2:1, 1:1 and 1:2 (w/w, denoted as WPI/zein-2/1, WPI/zein-1/1 and WPI/zein-1/2, respectively) were obtained. With few exceptions, composite films were successfully prepared by using deionized water and 25%, 50%, 75% or 95% ethanol as film forming solvents for the spray-dried powders. Physicochemical properties including thickness, moisture content, color parameters, transparency, mechanical properties, heat sealing properties, and water solubility were determined. Solvent types did not significantly affect the moisture content of composite films. For all three types WPI/zein powder, lower water vapor permeability was detected in films prepared with 75% and 25% ethanol. Composite films prepared with deionized water showed higher transparency. Brightness and white index of films decreased as the ethanol concentration in film forming solution increased. Maximum elongation and break elongation of films increased as the WPI content increased, while higher ethanol concentration exerted lower elongation. All composite films could be heat-sealed and had good hot water solubility.