Modeling rheological properties of low-in-fat o/w emulsions stabilized with xanthan/guar mixtures

The incorporation of hydrocolloids is a suitable alternative to stabilize low-in-fat o/w emulsions against creaming. The effect of composition on rheological properties and stability of low-in-fat o/w emulsions formulated using xanthan/guar gum mixtures in an acidic aqueous solution containing 2% NaCl was studied. A central composite design involving oil fraction and gum content was used. Frequency sweeps showed that both G' and G '' increased with oil content. However, the viscoelastic behavior was mainly governed by the hydrocolloid content. The shear-thinning behavior of both aqueous dispersions (continuous phases) and emulsions was successfully modeled with Ellis equation. Mooney equation was used to obtain the shape factor and maximum packaging volume fraction. Zero shear viscosity was also predicted based on emulsion composition by response surface methodology. Droplet size distribution was measured by light scattering; microscopic observations revealed a flocculated system. Visual inspections of the formulated emulsions showed that they remained stable after eight months. (C) 2008 Elsevier Ltd. All rights reserved.