Dynamic mechanical thermal analysis of aqueous sugar solutions containing fructose, glucose, sucrose, maltose and lactose

The glass transition of glucose, fructose, lactose, maltose and sucrose sol utions at maximum cryo-concentration was studied by Dynamic Mechanical Ther mal Analysis (DMTA), using the disc bending technique. The glass transition temperatures were determined from the peaks in the loss modulus E'', which corresponds theoretically to the resonance point (Maxwell model) for sever al input frequencies. The frequency dependence was well described by both a n Arrhenius-type model and by the WLF (Williams, Landel and Ferry) equation , yielding glass transition temperatures for an average molecular vibration time of 100 s, which were similar to published midpoint temperatures deter mined by DSC scans. Some sugar mixtures were studied, yielding results that were well described by the Gordon-Taylor equation, using literature data. The frequency dependence of the viscoelastic ratio was also well approximat ed by an Arrhenius-type equation, with activation energies similar to those of the glass transition temperature and corresponded well to published val ues of the endset of glass transition.