COMPETITIVE ADSORPTION OF BETA-LACTOGLOBULIN + TWEEN 20 AT THE OIL-WATER INTERFACE

Competitive adsorption is investigated at the oil-water interface for a mixture of a globular protein beta-lactoglobulin and a non-ionic surfactant Tween 20. Up to a surfactant-to-protein molar ratio of 1:1, addition of Tween 20 leads to a dramatic lowering of the surface viscosity of adsorbed beta-lactoglobulin at the n-tetradecane-water interface (10(-3) wt.% protein, pH 7, 25-degrees-C) but no significant change in the amount of beta-lactoglobulin adsorbed in an n-tetradecane-in-water emulsion (0.5 wt.% protein, 10 wt.% oil, pH 7). At a surfactant-to-protein molar ratio of 8:1, there is complete protein displacement from the emulsion droplet surface. The results are discussed in relation to a recent study of Tween 20 + beta-lactoglobulin in foams and thin films.