Effect of Spray Drying Conditions on the Physicochemical Properties and Enthalpy Relaxation of α-Lactose

Abstract

The purpose of this work was to investigate the effect of different spray drying conditions on the physicochemical properties of dried lactose. Results indicated that the feed concentration and inlet temperature, as well as storage condition, influenced the thermal properties of the dried material, which were evaluated by the degree of molecular relaxation, presumably associated to different levels of molecular mobility in the sample. It was evident that higher drying temperatures decreased molecular mobility of the dried material while increasing its glass transition and crystallization temperatures. This is most likely due to the existence of states of lower mobility within the material as those with higher mobility were relaxed. The change in heat capacity at the glass transition temperature, , and the reduced crystallization temperature, , were used to compare the crystallization tendencies of the spray dried powders. It was observed that a decrease in and an increase in were associated with higher crystallization temperatures. On the other hand, the enthalpic relaxation did not change significantly with storage conditions. The findings illustrated that the initial enthalpy relaxation, which occurred during spray drying, was related to the crystallization tendencies and storage conditions.