The rheological properties of other mixed protein films formed at the air-water interface (and in some cases oil-water interfaces) were also shown to be dependent on the composition, protein type and concentration of the constituents in the bulk phase. Indeed, a number of studies examined the co-adsorption of globular/globular or globular/random-coil protein mixtures at air-water or oilwater interfaces, and quantified the interfacial mechanics of resulting protein assemblies using dilatational rheology . Proteins with different structures were proposed to have different abilities to undergo conformational reorganisation at interfaces. The compatibility of two proteins and the mechanical properties of the resulting complex are mainly determined by the molecular weight of the proteins, the conformation state of the proteins at the interface, protein-protein interactions and proteins-solvent interactions . Studies showed that the composition of proteins in a mixed film is determined by the incompatibility of mixing of the adsorbing proteins with those in the interfacial film. The presence of the protein that arrives first at the interface was proposed to affect the binding affinity of the second protein. Although the changes in interfacial rheology observed for single protein assemblies (b-casein and BSA separately) are in good agreement with interfacial shear rheology data previously reported, they also point to significant differences compared to dilatational moduli observed . Specifically, whereas bcasein is associated with a significant reduction in surface pressure and dilatational moduli, the interfacial shear moduli of assemblies measured at Novec 7500 interfaces remained mainly unchanged. This points to the significant contribution of surface tension and pressures to the measured dilatational moduli, which are not relevant to shear moduli measured in the absence of changes in surface area. Although the interfacial shear mechanics of mixed b-casein/BSA interfaces has not been reported yet at other oil or air interfaces, it is however interesting to note that b-casein was found to dominate the dilatational mechanics of b-casein/b-lactoglobulin assemblies .