The glass transition and dielectric secondary relaxation of fructose-water mixtures.

Broad-band dielectric measurements for fructose−water mixtures with fructose concentrations between 70.0 and 94.6 wt% were carried out in the frequency range of 2 mHz to 20 GHz in the temperature range of −70 to 45 °C. Two relaxation processes, the α process at lower frequency and the secondary β process at higher frequency, were observed. The dielectric relaxation time of the α process was 100 s at the glass transition temperature, Tg, determined by differential scanning calorimetry (DSC). The relaxation time and strength of the β process changed from weaker temperature dependences of below Tg to a stronger one above Tg. These changes in behaviors of the β process in fructose−water mixtures upon crossing the Tg of the mixtures is the same as that found for the secondary process of water in various other aqueous mixtures with hydrogen-bonding molecular liquids, polymers, and nanoporous systems. These results lead to the conclusion that the primary α process of fructose−water mixtures results from the coop...