The effects of variable concentrations of different molecular weight fractions of dextran on the interfacial free energies and the kinetic coefficients of the overall linear growth rates of the sucrose crystal were evaluated at 40 and 50 degrees C. Dextrans-reducing effects on the interfacial free energy increased the overall linear growth rates of sucrose at 40 degrees C. Further, dextrans-reducing effects of the growth kinetic coefficients resulted in lower growth rates of the sucrose crystals at 50 degrees C. Impurity effectiveness factor, differential heat of adsorption and Langmuir isotherm constant were determined, for the used dextrans, at 50 degrees C and relative supersaturation of 0.161. The dextran of molecular fraction of 2000 kilo Daltons (kDa) showed considerably high effectiveness factor in comparison with the dextrans of molecular fractions of 70 and 250 kDa. Role of dextran in retarding the advancement of the growth steps in the vicinity of its incorporation on the face (100) of the sucrose crystal is pointed out using AFM technique. (C) 2012 Elsevier B.V. All rights reserved.