Solid-phase crystallization of spray-dried glucose powders: A perspective and comparison with lactose and sucrose

Abstract

The solid-phase crystallization growth kinetics of spray-dried sugar powders, including glucose, lactose and sucrose, have been studied from water-induced crystallization experiments at a relative humidity of 75% and temperatures from 15 to 40°C on amorphous powders of these sugars produced in a laboratory-scale spray dryer (Buchi B290). All results have shown that the enthalpies and Gibbs Free Energies of activation of the sugars studied here increase during the crystallization process, suggesting that the binding energy needed for the formation of an activated complex increases as the moisture content decreases. The enthalpies of activation for glucose, lactose and sucrose crystallization have been compared by the Activated Rate equation and found to be 58±8kJmol−1, 39±2kJmol−1 and 68±4kJmol−1, for glucose, lactose and sucrose, respectively, Similarly, the entropies of activation have been calculated as −92±27Jmol−1K−1, −156±6Jmol−1K−1 and −60±5Jmol−1K−1 for glucose, lactose and sucrose, respectively. These different numerical values may be expected from the different structures of the sugars.