Investigation of protein foams obtained by bubbling

Abstract

The foaminesses ζ of bovine serum albumin solutions, (BSA) with and without buffer, salt and alcohol additives were measured by bubbling and their surface tensions σ were obtained as function of the timet. The timet DG , which is necessary to attain the equilibrium surface tension is long (∼15 h). The area requirement of a single surface adsorbed moleculeA j0 was obtained fromdσ/dc, wherec the surfactant concentration, by the Gibbs relation. By assuming the existence of a hydration complex, which consists of the surfactant andX water molecules, the,coordination numbers were estimated toX=12±1 fromA j0 and the surface requirement of the hydrophilic group of the surfactant. The dependences of CMC andX on the additives are discussed. A good relation prevails between ζ andt DG . By applying the phase change model of Avrami for the adsorption and surface denaturation of theBS A, simple relation was found between the dimensionless surface tensionV = (σ0 - σs∞) ∼ (σst-σs∞) and the timet: log (2.3 logV) =n logt + logb The good relations between ζ andn as well as between ζ andnb indicate the applicability of this model.