DIFFERENCES IN THE STRUCTURE AND DYNAMICS OF THE ADSORBED LAYERS IN PROTEIN-STABILIZED MODEL FOAMS AND EMULSIONS

Protein-stabilized food dispersions often contain a range of surface a ctive species. Many of these are of low molecular weight and include l ipids or food emulsifiers. Depletion measurements, fluorescence and fl uorescence recovery after photobleaching (FRAP) studies have shown tha t competitive adsorption of these molecules at the interface causes br eakdown of protein-protein interactions in the adsorbed layer. This re sults in partial displacement of adsorbed protein and the initiation o f lateral diffusion in the remaining adsorbed fraction However, there are distinct differences between the structure of the adsorbed protein layers found at air/water and oil/water interfaces. This causes diffe rences in behaviour of the adsorbed layer in response to competitive a dsorption of low-molecular-weight surfactant. This paper contrasts the behaviour of adsorbed layers formed by the milk proteins, beta-lactog lobulin and beta-casein, adsorbed at the interfaces of air-suspended t hin liquid films and the thin aqueous him between two oil droplets, as a function of increasing concentration of the non-ionic surfactant, T ween 20.