Structure, Miscibility, and Rheological Characteristics of ß-Casein-Monoglyceride Mixed Films at the Air-Water Interface

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, miscibility, and interactions) and dynamic characteristics (surface dilatational properties) of β-casein and monoglyceride (monopalmitin and monoolein) mixed films spread on the air-water interface. The static and dynamic characteristics of the mixed films depend on the interfacial composition and the surface pressure. At higher surface pressures, collapsed β-casein residues may be displaced from the interface by monoglyceride molecules with important repercussions on the interfacial characteristics of the mixed films. From the frequency dependence of the surface dilatational properties, we have elucidated the relationships between interfacial dilatational rheology and changes in molecular structure, interactions, miscibility, and relaxation phenomena in protein-monoglyceride mixed films.