Static and dynamic properties of a whey protein isolate and monoglyceride mixed films at the air-water interface

The static and dilatational properties of mixed emulsifiers are of interest due to their importance in relation to dispersion formation and stability. In this work, we have used different and complementary interfacial techniques (surface film balance, Brewster angle microscopy, and interfacial dilatational rheology), to analyze the static (structure, morphology, reflectivity, and miscibility) and dynamic (surface dilatational properties) characteristics of whey protein isolate (WPI) and monoglyceride (monopalmitin or monoolein) mixed films spread on the air-water interface. The static and dynamic characteristics of the mixed films depend on monolayer composition and the surface pressure. At higher surface pressures, collapsed WPI residues may be displaced from the interface by monoglyceride molecules with important repercussions on the interfacial characteristics of the mixed films. A close relationship between interfacial dilatational rheology and changes in molecular structure interactions miscibility and relaxation phenomena has been established from the frequency dependence of the surface dilatational properties.