A quantitative DSC analysis of the metastable phase behavior of the sucrose–water system

The phase behavior of the sucrose–water system is investigated using a quantitative calorimetric analysis. On the basis of a thermodynamic discussion of the melting behavior of the crystalline water component, the composition of the metastable amorphous phase and the so-called maximum freeze-concentrated composition were determined. This metastable phase can be described in a first approximation as an association complex consisting of one molecule of sucrose and five molecules of water which are held together by hydrogen bonding. The critical mass fraction of sucrose is thus 0.792. Furthermore, the origin of the different transitions in the aqueous phase is discussed. By analyzing the ice melting, an analytical relationship of the water activity coefficient is derived from the experimental data.