Effect of soya oil and glycerol on physical properties of composite WPI films Original Research Article

The water vapour permeability (WVP), mechanical strength, equilibrium moisture content (MC), glass transition temperature and opacity of whey protein isolate films plasticised with different levels of glycerol (Gly) (glycerol:protein (Gly:Pr)=0.5, 0.6 and 0.7) and containing different levels of added soya oil (oil:protein (Oil:Pr) ratio=0.0, 0.2, 0.3 and 0.4) were measured. Increasing oil concentration led to increases in percent elongation (EL), glass transition (Tg) temperature, and decreases in MC, tensile strength (TS), and elastic modulus (EM), but did not affect the WVP of films. Increasing levels of Gly led to increases in percent EL, MC and decreases in TS, EM, Tg and film opacity.