Physical and mechanical properties in biodegradable films of whey protein concentrate-pullulan by application of beeswax

Different ratios of whey protein concentrate (WPC):pullulan (PUL) (70:30,50:50, 30:70%w/w) and various rates of beeswax (BW) (0, 10, 20, and 30%W/W-glycerol) were applied to prepare biodegradable WPC-PUL films containing glycerol as a plasticizer, for the first time. Thickness, moisture content, water solubility, water vapour permeability, colour, and mechanical properties of prepared films were measured. Higher ratios of WPC:PUL led to more desirable physical and mechanical properties; in other words, lower rates of thickness, moisture content, water solubility and water vapour permeability, and higher elongations were achieved. Application of BW (especially in higher contents) could successfully improve colour indices, diminish water solubility (nearly 12%) and water vapour permeability (approximately 3 x 10(-11) g m(-1) s(-1) Pa-1) and increase tensile strength (by about 7 MPa) of WPC-PUL blend films. Our edible films enjoyed great whiteness and ignorable yellowness indices, making it a suitable alternative for application in food products. Overall, WPC70-PUL30 containing 30% BW resulted in the best performance of physical and mechanical aspects as an optimum film. (C) 2014 Elsevier Ltd. All rights reserved.