Influence of increasing viscosity of the aqueous phase on the short-term stability of protein stabilized emulsions

The emulsification process includes two steps. First, deformation and disruption of droplets, and secondly, stabilization of the newly formed interfaces by surfactants. Emulsions are thermodynamically unstable, as droplets tend to coalesce. To avoid coalescence of droplets, different effects have to be taken into account. Hydrodynamic stabilization by slowing down the drainage of the liquid between two colliding droplets is one of these effects. The objective of this paper is to investigate the possibility of producing finely dispersed emulsions by increasing the viscosity of the continuous phase even using poor stabilizing surfactants. Experiments were carried out using proteins as surface active agents. To increase the viscosity of the continuous phase. stabilizers of different molecular weights were used in order to change the conditions for interactions between proteins, stabilizers and the emulsion droplets. The results are compared to those obtained with a model system containing surfactant and stabilizer of the same type of molecule (polyvinyl alcohol), realizing a system without additional interactions between stabilizer and surfactant. The results presented in this Study have shown that by adding stabilizers not only a better stability of the emulsion is achieved: depending on the molecule structure of the stabilizer, also destabilizing effects such as inhibition of protein adsorption and isotropic/anisotropic phase separation may occur. (C) 2002 Elsevier Science Ltd. All rights reserved.