An isothermal ice recrystallization behavior in trehalose solution was investigated. The isothermal recrystallization rate constants of ice crystals in trehalose solution were obtained at -5 A degrees C, -7 A degrees C, and -10 A degrees C. Then the results were compared to those of a sucrose solution used as a control sample. Simultaneous estimation of water mobility in the freeze-concentrated matrix was conducted by H-1 spin-spin relaxation time T-2 to investigate mechanisms causing the different ice crystal recrystallization behaviors of sucrose and trehalose. At lower temperatures, lower recrystallization rates were obtained for both trehalose and sucrose solutions. The ice crystallization rate constants in trahalose solution tended to be smaller than those in sucrose solution at the same temperature. Although different ice contents (less than 3.6%) were observed between trehalose and sucrose solutions at the same temperature, the recrystallization behaviors of ice crystals were not markedly different. The H-1 spin-spin relaxation time T-2 of water components in a freeze-concentrated matrix for trehalose solution was shorter than in a sucrose solution at the same temperature. Results show that the water mobility of trehalose solutions in freeze-concentrated matrix was less than that of sucrose solutions, which was suggested as the reason for retarded ice crystal growth in a trehalose solution. Results of this study suggest that the replacement of sucrose with trehalose will not negatively affect deterioration caused by ice crystal recrystallization in frozen foods and cryobiological materials.