In this work we have used different and complementary interfacial techniques (surface film balance, Brewsterangle microscopy, and interfacial shear rheology), to
analyze the static (structure, topography, reflectivity,miscibility, and interactions) and flow characteristics (surface shear characteristics) of milk protein (
-casein,caseinate, and
-lactoglobulin) and monoglyceride (monopalmitin and monoolein) mixed films spread andadsorbed on the air-water interface. The structural, topographical, and shear characteristics of the mixedfilms depend on the surface pressure and on the composition of the mixed film. The surface shear viscosity(
s) varies greatly with the surface pressure (
). In general, the greater the
values, the greater were thevalues of
s. Moreover, the
s value is also sensitive to the miscibility and/or displacement of film-formingcomponents at the interface. At surface pressures lower than that for protein collapse, protein and monoglyceridecoexist at the air-water interface. At surface pressures higher than that for the protein collapse, a squeezingof collapsed protein domains by monoglycerides was deduced. Near to the collapse point, the mixed film isdominated by the presence of the monoglyceride. Different proteins and monoglycerides show differentinterfacial structure, topography, and shear viscosity values, confirming the importance of protein andmonoglyceride structure in determining the interfacial characteristics (interactions) of mixed films. The valuesof
s are lower for disordered (
-casein or caseinate) than for globular (
-lactoglobulin) proteins and forunsaturated (monoolein) than for saturated (monopalmitin) monoglycerides in the mixed film. The displacementof the protein by the monoglycerides is facilitated under shear conditions.
