Effect of H2O-CO2 organization on ovalbumin adsorption at the supercritical CO2-water interface

We have studied the formation of water-CO2 interfaces in the presence of different concentrations of ovalbumin (OVA) by tensiometry and by means of interfacial rheological measurements to obtain some information on the capacity of protein film to stabilize H2O in CO2 emulsion. The formation of pure water-CO2 interface can be described as a two-step phenomenon.(1) The CO2 molecules adsorb onto the water surface and then a reorganization of the interface creates a H2O-CO2 cluster network. This organization occurs at a temperature (40 degreesC) higher than the higher temperature limit (10 degreesC) allowing the formation of crystalline structure called CO2 clathrate.(2) Our results show that ovalbumin adsorption from bulk concentrations higher than 0.0229 g/L inhibits the cluster formation for a CO2 pressure less than 80 bar. However, for lower concentrations, the more the CO2 pressure is close to 80 bar, the more OVA adsorption is reduced by the H2O-CO2 cluster network. Moreover, from a pressure of 90 bar, the affinity of OVA for the interface increases and mixed films made of protein molecules and clusters are obtained for the OVA concentrations lower than I g/L.