Thermodynamic properties and kinetics of the physical ageing of amorphous glucose, fructose, and their mixture

The physical ageing characteristics of glucose, fructose, and their mixtures were studied using standard differential scanning calorimetry (DSC). The inflection, onset, midpoint, half-height, and endpoint glass transition temperature (T_g), fictive temperature (T_f), and relaxation enthalpy (ΔH) were measured as a function of ageing time. The relationship between ΔH and T_f was evaluated. The time dependence of ΔH was fit using the Cowie and Ferguson model. The ageing rate was expressed in terms of the average relaxation time (〈τ〉) and the entropy production (P). It was found that the fructose component decreased the rate of ageing of the mixtures.