Osmotic dehydration (OD) of carambola slices in sucrose, fructose and glucose solutions has been carried out to evaluate water and solute diffusivities, as well as the final impregnation-dehydration levels of the fruit. OD kinetics was performed in sugar solutions (50 g/100 g) at 45, 60 and 75 degrees C during 10 h using a syrup-to-fruit mass ratio of 15:1. An analytical solution for unsteady-state mass transfer based on Fick's second law of diffusion was used for the mathematical description of water loss and solute gain kinetics. By following a central composite design, additional OD tests were conducted to evaluate the effect of solute concentration (35.9-64.1 g solute/100 g solution) and process temperature (38.8-81.2 degrees C) on the equilibrium and distribution data for both solutes and water. Under the described experimental conditions, effective water diffusivity was in the range of 1.00-3.74 x 10(-9) m(2)/s, whereas values for sucrose, fructose and glucose diffusivities were between 0.58-1.79 x 10(-9), 0.56-1.34 x 10(-9) and 0.56-1.88 x 10(-9) m(2)/s, respectively. Results demonstrated that sucrose can be considered a better osmotic agent than fructose and glucose for OD of carambola, favoring greater water loss-to-solute gain ratios at comparable mass transfer rates. (C) 2010 Elsevier Ltd. All rights reserved.