Therefore these results suggest that replacement of a pool of BSA adsorbed at oil-water interfaces Protein exchange experiments highlighted the impact that the first adsorbed protein layer has on further maturation of protein compositions and interfacial mechanics as adsorption of additional proteins takes place. Such processes are particularly relevant to the maturation of protein interfaces and were found to significantly impact interfacial shear mechanics and elasticity. Hence exposure of BSA adsorbed layers to free b-casein resulted in the displacement of a pool of BSA proteins and some level of softening of resulting assemblies. It is not clear why the elasticity of these systems did not increase as was observed in the case of binary adsorption from mixed BSA and bcasein solutions (at low concentration of b-casein, 2 and 5%), but possibly results from different architectures for the networks formed. Interestingly, this contrasts with the striking impact that adsorption of very low levels of BSA proteins onto a pre-adsorbed b-casein layer had on interfacial mechanics and elasticity.