Glass transition, ice and the concentration of the maximally freeze-concentrated solution: The thermal behavior of sugar solutions

As solutions of sugars freeze, the sugar solution between the ice crystals becomes more concentrated until it reaches a point at which viscosity prevents ice crystal growth is and the solution becomes glassy. The maximum concentration of solutes remaining after all possible ice has frozen is called the concentration of the maximally freeze concentrated solution (C{dollar}sb{lcub}rm g{rcub}spprime{dollar}). The temperature at which this solution changes from a glass to a viscous liquid is called the glass transition of the maximally freeze concentrated solution (T{dollar}sb{lcub}rm g{rcub}spprime{dollar}). This transition can be measured using differential scanning calorimetry. Many thermal events occur at temperatures near to T{dollar}sb{lcub}rm g{rcub}spprime{dollar}. This has caused some confusion and some disagreement in literature values for T{dollar}sb{lcub}rm g{rcub}spprime{dollar}. A method is described for the determination of T{dollar}sb{lcub}rm g{rcub}spprime{dollar} and C{dollar}sb{lcub}rm g{rcub}spprime{dollar}. Results for solutions of sucrose, glucose, fructose, maltose, xylitol, and sorbitol in water are presented. Values found for T{dollar}sb{lcub}rm g{rcub}spprime{dollar} and C{dollar}sb{lcub}rm g{rcub}spprime{dollar} agree reasonably with published values. Data are also presented for solutions of sucrose and fructose in water. These show the relationship of component proportions to T{dollar}sb{lcub}rm g{rcub}spprime{dollar}, C{dollar}sb{lcub}rm g{rcub}spprime{dollar}, the beginning of ice melting, the apparent glass transition and the overshoot peak for solutions that form ice and the glass transition of non-ice forming solutions.