Fig. 2 shows a typical plot of conductivity (mS/cm) vs time (min) for corn oil in water emulsion using egg white, as emulsifier, with a concentration of 0.5 mg/ml, for several oil volume fractions (OVF). The data were fit to the sigmoid function, Eq. (3). In general, the conductivity vs time curve for egg white-stabilized edible oil emulsions is characterized by a short period (lag time) where the conductivity of an emulsion remains essentially equal to that during the homogenization period. This metastable condition soon diminishes once flocculation and creaming phenomena take place. The latter events are manifested by an increase in conductivity values that show a non-linear concave up slope. Finally, a phase separation takes place, which is manifested by a steady-state plateau value.
As shown in Fig. 2, the shape of the plot is characterized by a non-zero lag time, unlike Langmuirian or Freundlich types. Expressing the emulsion stability simply in terms of initial events that occur just after homogenization is stopped, as was done by Kato et al. (1985), was found inappropriate in this case (i.e. for egg white-stabilized o/w emulsions). Moreover, the presence of a non-zero lag time and a relatively concave up curve that is not necessarily linear in the first region makes it also unsuitable to divide the conductivity curve into two regions; namely, an initial linear region characterized by a higher slope; and a final linear region characterized by a lower slope as suggested by Suttiprasit et al. (1993).