Apple, orange and pineapple juices were used to prepare thickened fluids from six Australian commercially available food thickeners that are based on guar gum, modified starch and xanthan gum. Using a strain-controlled rheometer, changes in shear stress with the rate of shear (1-100 s(-1)) at 20 degrees C were independent of the thickener or fruit juice. As the solids content of the fluids increased, so were the viscosity, density and extrapolated yield stress. The density, yield stress and viscosity of the thickened fluids were not significantly influenced (p > 0.05) by fruit juice, but the type of thickener significantly (p < 0.05) affected these properties. The Herschel-Bulkley model was found to be the most suitable in describing the theological data of the thickeners in the fruit juices. The relevant parameters obtained for the recommended models can be used to obtain a known viscosity of the thickened fluids, match to fluids used in videofluoroscopy and obtain objective classification of the thickened fluids. Sample calculations are included. (C) 2007 Elsevier Ltd. All rights reserved.