Calorimetric study of the glass transition occurring in aqueous glucose: Fructose solutions

Glass transition temperatures (T_g) for dilute and concentrated glucose: fructose: water solutions have been determined by differential scanning calorimetry. The supplemented phase diagrams (glucose: fructose 1:4, 1:2, 1:1, 2:1, 4:1 (w/w)) are presented and from these the temperature (T_g') and concentration (C'_g) of the maximally freeze-concentrated glass have been determined. Theoretical predictions of T_g for binary (glucose: fructose) and tertiary (glucose: fructose: water) systems according to the Couchman–Karasz and Gordon-Taylor equations are given and discussed. Annealing vitrified glucose: fructose glasses above their T_g allows the glass concentration to approach C'_g as a result of ice formation. Viscosity measurements of fructose and fructose: glucose mixtures allow for a calculation of T_g of the non-aqueous solutions.