Characteristics of dehydration kinetics of dihydrate trehalose to its anhydrous form in ethanol by DSC

Dehydration of dihydrate trehalose to its anhydrous form was performed via crystal transformation in a pressure pan with a differential scanning calorimeter using ethanol as the drying medium. The effect of water content of ethanol on the dehydration kinetics was investigated by differential scanning calorimetry (DSC), under two experimental conditions: isothermal and temperature ramping. The data sets collected were analysed by the Avrami equation and the Arrhenius plots for isothermal conditions and by Kissinger’s method for non-isothermal measurements. The Kissinger plots revealed click point temperatures (CPTs) which were dependent on the water content of ethanol. At temperatures below the CPTs, higher activation energies were found, whereas at temperatures above the CPTs, lower activation energies were estimated. The anhydrous trehalose crystals obtained by crystal transformation using ethanol of 0.005–2.5% water content were visually observed as aggregates of nano-sized acicular crystals, which inherited the shapes of the dihydrate trehalose crystals.