Surface properties of the bovine casein components: relationships between structure and foaming properties

Abstract

SummaryIn order to optimize the use of caseins as surfactants, the surface tension, foaming capacity and stability were measured as a function of pH, ionic strength, protein concentration and polarity (modified by covalent binding of carbohydrates). We found that the caseins differ in their behaviour at the air/water interface with β-casein showing the greatest ability to decrease surface tension and to produce foams, due probably to its amphipathic structure. In experiments carried out at pH values close to pI, with low ionic strength and constant solubility (optimal conditions for foam formation), we observed a high surface hydrophobicity, a good accessibility and flexibility of peptidic side chains (evaluated by proteolysis), and a high foaming capacity parallelled by increased surface pressure. Foam stability of caseins was low compared to those of globular proteins such as β lactoglobulin.