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Abstract: The aim of this work was to get further insight into the formation of the interfacial film by ovalbumin and lysozyme in equimolar binary solutions, as well as the organization of these proteins inside the interfacial film. Our approach consisted in the sequential adsorption of the two proteins, with or without previous replacement of the sub-phase with protein-free buffer before injection of the second protein. The results suggest that ovalbumin controls surface pressure of the interfacial film and whatever the order of adsorption, there would be a specific and stratified organization of the two proteins inside the interfacial film: an ovalbumin monolayer in direct contact with the air–water interface and multilayers of lysozyme below this top layer. The experiments of replacement of the sub-phase suggest that, for both proteins, the adsorption film is almost resistant to this replacement with protein-free buffer, showing an apparently irreversible adsorption for the time-scale considered and at high concentrations. Moreover, the synergy between ovalbumin and lysozyme put into evidence during the concomitant adsorption of the two proteins in a previous work (, Food Hydrocolloids 23, 352–365) is a phenomenon which occurs as the result of adsorption of the proteins at the air–water interface. [Copyright &y& Elsevier]

Abstract: This study was undertaken to characterize the interfacial and foaming properties of different mixtures at the air–water interface under the same concentration range, and to put into light putative particular behaviors of mixtures. Different complementary techniques have been coupled such as null ellipsometry, surface tension and shear elastic constant measurements as well as polarization-modulation infrared reflection–absorption spectroscopy (PM-IRRAS). Moreover, the foaming properties were also investigated by a bubbling method. Solutions of either ovalbumin or lysozyme exhibit different interfacial behaviors. Ovalbumin does not form multilayers, even at high concentration. Conversely, lysozyme forms films that are much thicker than a protein monolayer whereas the surface pressure is definitely smaller than that ovalbumin. It thus seems that ovalbumin is much more surface active than lysozyme. The ellipsometric angles for the binary mixtures are much higher than those of films formed by the pure proteins, independently of the molar ratio. These results suggest that there is a synergy in the interfacial adsorption between the two proteins, which is confirmed by PM-IRRAS measurements, most likely due to the electrostatic interactions between the oppositely charged lysozyme and ovalbumin. Moreover, shear elastic constant measurements suggest that lysozyme has a strong effect on the organization of the interfacial film. The foaming properties of the mixtures are, however, always close to those of the pure ovalbumin solution. Therefore, lysozyme does not foam alone, but is able to foam as well as pure ovalbumin after addition of a very small amount of ovalbumin, which suggests that the synergy between proteins has an impact on the foaming properties. [Copyright &y& Elsevier]