Interfacial Interactions, Competitive Adsorption and Emulsion Stability

Food emulsion stability is strongly influenced by the interactions in the adsorbed layer around emulsion droplets. Competitive adsorption of pure milk proteins (13-casein or 13 -lactoglobulin) with nonionic surfactants in oil-in-water emulsions is shown to depend on the age of the adsorbed protein layer. Evidence is presented for slow accumulation of protein at the oil-water interface and/or partition of protein into the oil phase of emulsion droplets containing oil-soluble surfactant associated in reversed micelles. Small amounts of added water-soluble surfactant or calcium ions are shown to have a pronounced effect on the droplet coalescence rate under turbulent shear flow conditions. It appears that orthokinelic emulsion stability is related to the composition and surface rheology of the adsorbed layer and to the degree of perikinetic flocculation of the emulsion droplets.