Transitions in aqueous solutions of sucrose at subzero temperatures

Classical and temperature-modulated DSC methods were employed to study aqueous solutions of sucrose in the whole concentration range and the temperature interval of -120 degrees C to 30 degrees C. New interpretation of experimental data based on the state diagram has shown that transitions observed at temperatures below the melting temperature of ice are glass transitions of two amorphous phases in the system-the maximally freeze-concentrated phase (MFCP) and the solution surrounding sucrose crystals. At low temperatures, these solutions pass into the glassy state. Structure Of these frozen solutions is inhomogeneous. It includes at least two crystalline phases and two amorphous glasses. This behavior is characteristic of diluted and semiconcentrated solutions. The solutions of composition close to the eutectic one usually freeze directly into glass; during re-heating water crystallizes and a liquid phase is separated with a concentration differing from the original concentration of the initial solution.