An Attempt at Evaluating Stability of Egg-white Foams on the Basis of Rheological Measurements

Abstract

The stability of egg-white foams could be characterized by the changes in viscoelastic properties within the measurements of creep behaviors or stress relaxation. The instantaneous elasticity or initial relaxation modulus increased with increasing time for about 40 min after the preparation of the foams according to the slow rate of adsorption of egg albumin on the air/water interface. These moduli then decreased, while the aging time after the preparation increased due to the thinning and rupture of the liquid films in the foams. The rates of decreasing moduli were accelerated by the reducing concentration of sugar and by the lowering pH in the egg-white. The presence of sugars seems to control the drainage rate of water from the liquid films, while the electrostatic repulsion between the adsorbed layers of albumin in the liquid films reduces in acidic region due to the lowering charged potential on the surface of the adsorbed layer.