COMPETITIVE ADSORPTION BETWEEN SODIUM CASEINATE AND OIL-SOLUBLE AND WATER-SOLUBLE SURFACTANTS IN OIL-IN-WATER EMULSIONS

Competitive adsorption between sodium caseinate and either a water-soluble surfactant, Tween 60 (polyoxyethylene sorbitan monostearate-PSM) or an oil-soluble surfactant, Span 60 (sorbitan monostearate-SM) was studied in oil-in-water emulsions. Surfactants were present during homogenization. Surface concentration of protein in freshly prepared emulsions decreased as concentration of PSM or SM increased. However, only partial displacement of protein was observed with either surfactant. The reduction in protein surface concentration was greater in the presence of PSM. Interfacial protein composition was independent of surfactant type. In the absence of surfactant, preferential adsorption of beta-casein occured in emulsions containing less than or equal to 1.0 wt % protein. On addition of surfactant preference for beta-casein at the interface was reduced.