Transformation of lactulose trihydrate into anhydrous lactulose by fluidized bed drying and its characterization.

Stable anhydrous lactulose was produced from lactulose trihydrate by stepwise heating on a fluidized bed. The processes were performed on stable powder forms. The anhydrous lactulose was characterized by an opaque white appearance, a coarse surface structure with random cracks and indentations, a high degree of crystallization, stability under humid conditions, and by X-ray powder diffraction, differential thermal analysis, and differential thermogravimetry. Those characteristics were different from those of the original trihydrate, which was transparent, had a smooth surface and a higher degree of crystallization, was stable under humid conditions and had different X-ray powder diffraction, differential thermal analysis, and thermogravimetric characteristics. The transformation was enhanced when the inlet temperature was 45-55 degrees C or when the temperature of the fluidized bed was over 40 degrees C. At these cutoff temperatures, both crystalline forms were observed.