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 (beta-casein or beta-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 accumulati on of protein at the oil-water interface and/or partition of protein i nto the oil phase of emulsion droplets containing oil-soluble surfacta nt associated in reversed micelles. Small amounts of added water-solub le surfactant or calcium ions are shown to have a pronounced effect on the droplet coalescence rate under turbulent shear flow conditions. I t appears that orthokinetic emulsion stability is related to the compo sition and surface rheology of the adsorbed layer and to the degree of perikinetic flocculation of the emulsion droplets.