Dynamic and sub-ambient thermal transition relationships in water-sucrose solutions

This work was undertaken to investigate thermal and dynamic transitions observed in the temperature range close to the bulk ice melting temperature in sucrose solutions. Measurements of thermal (differential calorimetry) and dynamic (neutron scattering) properties were compared in order to give a physical interpretation of the thermal transitions observed during the thawing of amorphous sucrose solutions. In fact, the freezing of biological material leads to the distinction between different pools of water: bulk water which becomes ice after freezing, unfrozen water trapped in the glassy matrix or close to the interface of solutes can be considered, and finally freezable confined water with a lower melting point than bulk water and with properties depending on both the ice presence and the microstructure of the material. The transition temperatures such as glass transition or melting are dependent on the freezing protocol used and examples of annealing effects are presented, in order to underline the necessity of a good temperature control during freezing for the study of biological material with freezable water.