Application of decolourised hsian-tsao leaf gum to low-fat salad dressing model emulsions: a rheological study

The effects of mixed gums, including decolourised hsian-tsao leaf gum (dHG) mixed with propylene glycol alginate (PGA) or xanthan gum (XG), and egg yolk concentration on the rheological properties of low-fat salad dressing model emulsions were studied. All model emulsions showed pseudoplastic flow behaviour. Model emulsions with PGA addition showed the lowest pseudoplasticity, followed by those with dHG and then XG addition. Increasing the PGA level in the dHG/PGA system reduced the pseudoplasticity. Increasing the XG level in the dHG/XG system did not change the pseudoplasticity significantly but imparted a significant increase in viscosity. Dynamic viscoelasticity measurements indicated that model emulsions with dHG or XG addition could be classified as elastic gels. However, model emulsions with PGA addition essentially belonged to the class of either dilute or concentrated solutions rheologically, depending on the egg yolk concentration. The rheological characteristics of individual gums were found to be confounded in generating the rheological characteristics of model emulsions containing them.