Crystallization of sucrose glass under ambient conditions: evaluation of crystallization rate and unusual melting behavior of resultant crystals.

Isothermal crystallization of sucrose glass under ambient condition was investigated by powder X-ray diffraction, isothermal microcalorimetry, and water sorption/desorption analysis. Isothermal microcalorimetry measurements showed that the crystallization behavior was affected by the compression force applied to starting amorphous materials. The crystallization rate was analyzed by X-ray diffraction measurements to establish that the rate could well be explained by the Avrami-Erofeev equation. In the water sorption/desorption analysis, the weight change during the crystallization was elucidated by supposing that desorption proceeded from the crystallized part. The sucrose crystallized at relatively low temperature conditions showed completely different melting behavior from that of intact sucrose, although the crystal form was most likely to be identical. This difference could be explained by defects in the lattice structure produced during the crystallization and the desorption process. Correlation was found between the melting temperature and the water content just before the crystallization. Defects in the crystal structure were partially modified by annealing as has been found in relaxation studies of amorphous materials.