Solid-phase crystal growth kinetics of spray-dried glucose powders

Abstract

To understand the solid-phase crystallization growth kinetics of glucose powders, a laboratory-scale spray dryer (Buchi B290) was used with aqueous solutions of glucose to create amorphous powders. The amorphous powders were placed in a sorption box at a relative humidity of 75% and six different temperatures (15°C, 20°C, 25°C, 30°C, 35°C and 40°C) for water-induced crystallization. The experimental results showed that the enthalpy and Gibbs free energy of activation of glucose increased during the crystallization process, which suggested that the binding energy needed for the formation of an activated complex increases as the moisture content decreases. The energy of activation for glucose crystallization has been found by the activated rate equation to be 58±8kJmol−1, and the entropy of activation was found to be −92±27Jmol−1K−1. A linear plot of compensation between the enthalpy and entropy of activation suggests that solid-phase crystallization for glucose is an entropy-controlled process.