A study of the rheological behavior of untreated and pasteurized carrot juice was carried out using a rotational viscometer at temperatures between 8 and 85 degrees C. The theological models of Newton, Bingham, Casson, Ostwald-De- Waele, Herschel-Bulkley and Mizhari-Berk were fitted to the experimental results. All models represented well the theological data, with high values for the correlation coefficients. The untreated carrot juice was well described by the Newtonian model, while the pasteurized juice showed a pseudoplastic behavior and was well fitted to all models except the Newtonian. The effect of temperature on viscosity was evaluated using an Arrhenius-type equation. The values obtained for the activation energy were 3.66 +/- 0.18 and 3.07 +/- 0.39 kcal mol(-1) for the untreated and pasteurized carrot juices, respectively. (C) 2008 Elsevier Ltd. All rights reserved.