Enthalpy relaxation of freeze concentrated sucrose–water glass

The enthalpy relaxation of freeze concentrated sucrose–water glass was investigated using 40% sucrose, differential scanning calorimetry (DSC) with isothermal ageing for 1–6 days at various temperatures (−70, −65, −60, and −55 °C). The enthalpy relaxation was observed as an endothermic peak superimposed on the endothermic step-wise change due to the glass transition around −47 °C. The enthalpy relaxation was found to increase with ageing time and temperature. An 80% sucrose glass was also investigated at ageing temperatures of −60 and −65 °C, and this material exhibited a similar glass transition and enthalpy relaxation to that observed with the frozen 40% sucrose solution. The calculated activation energy of the enthalpy relaxation of the sucrose–water glass was smaller than that reported for pure sucrose. These results suggest that the freeze concentrated sucrose–water glass could have a higher molecular mobility and less stability than pure sucrose glass.