Linear viscoelasticity of salad dressing emulsions

The effects of oil, emulsifier, and starch concentrations on the linear viscoelasticity of oil/water salad dressing emulsions were studied. Oil concentration ranged between 35 and 55 wt %. Emulsions were prepared using a mixture of egg yolk (0-6 wt %) and a highly hydrophilic sucrose ester (0-10 wt %) as emulsifier. Starch(O-2 wt %) was included in the formulation to study the influence of increasing continuous phase viscosity. The influence of the concentration of these components an the linear viscoelasticity functions was generalized by using the plateau modulus as a normalization factor. An increase in oil concentration did not qualitatively modify the linear viscoelastic behavior. A frequency displacement of the plateau region took place when egg yolk and sucrose ester concentrations were changed. Results were analyzed by calculating the relaxation time spectra of these emulsions. The BSW-CW model was used to fit these spectra. The pseudoterminal relaxation time increases with egg yolk concentration and decreases with sucrose ester concentration. The slope of the plateau region generally increases as oil or emulsifier concentration does but decreases with starch concentration. These results have been related to the formation of an extensive structural network in the emulsions.