Protein adsorption isotherms studied by axisymmetric drop shape analysis

Abstract

The pendant drop method is used to measure the interfacial tension isotherms of solutions of the model proteins β-casein, β-lactoglobulin both from bovine milk, and human serum albumin. A recently developed theory of protein adsorption at fluid interfaces [V.B. Fainerman, R. Miller, R. Wüstneck, J. Colloid Interface Sci. 183 (1996) 26] is used to calculate the equilibrium protein concentration at the interface and in the bulk. Comparison of the results with literature data obtained by plate and ring tensiometry shows that at low initial protein concentrations in a drop and a large surface area, the final protein concentration after the establishment of equilibrium can be significantly decreased. However, this deficiency of the pendant drop method is turned into an advantage, as from the mass balance of the protein at low initial the adsorption can be calculated.