The recrystallization of ice crystals in sucrose solution was investigated by cryo-SEM in a temperature range of -21°C to -50°C, including temperatures around Tg′. By using the technique of image analysis, the mean radius of the ice crystals was evaluated and recrystallization rates were calculated by a kinetic equation based on the Ostwald ripening principle. As the storage temperature decreased, a rapid decline in recrystallization rate was observed between -29°C and -35°C, which was consistent with the concept of glass transition of the freeze-concentrated matrix. Even at -50°C, at which the freeze-concentrated matrix was considered to be in glassy state, an increase in the mean crystal size was observed after 20hr storage.
2005 by Japanese Society for Food Science and Technology