Influence of xanthan gum and locust bean gum upon flow and thixotropic behaviour of food emulsions containing modified starch

Low oil content mayonnaises are food emulsions which exhibit shear thinning and thixotropic behaviour. They include generally modified starch in their formulation. In this work we study the effect of substituting part of this starch with other natural gums, such as xanthan gum or locust bean gum, upon the consistency and stability of the emulsions in relation to stirring. The gels prior to final emulsification have also been analyzed. Steady flow curves of all systems are well described by the Carreau model. The emulsions containing the greatest percentage of gums presented significantly higher viscosity than the reference emulsion and the emulsions containing the synergistic mixtures of xanthan gum and locust bean gum. To analyze the time dependency, thixotropic loops were performed. Both up curves and down curves fitted the Herschel-Bulkley model. Analysis of the relative thixotropic areas calculated by integration, showed that starch substitution with gums led to an increase in emulsions thixotropy. (c) 2006 Elsevier Ltd. All rights reserved.