Non-steady rheological behavior of oil-in-water emulsions stabilized by a sucrose palmitate

Abstract

Non-steady flow properties of concentrated oil in water emulsions containing oil (60-80% wt.), water and sucrose palmitate (1-5% wt.) of high hydrophilic-lypophilic balance were investigated. Stress growth, steady flow and linear viscoelastic measurements were carried out for this study. The emulsions studied exhibited a thixotropic behavior showing a very rapid stress overshoot. The stress decay was fitted to a Figoni-Shoemaker model using two exponentials. An stress undershoot was also produced under certain conditions. Shear brought about strong structural changes, such as droplet size redistribution at high oil content and temperature. Thus, the steady state viscosity does not fit an Arrhenius type equation with temperature. A shear thinning behavior was found for the steady state viscosity and the peak viscosity.