Freeze-drying: in situ observations using cryoenvironmental scanning electron microscopy and differential scanning calorimetry.

The quality of a freeze-dried product and the ease with which it can be reconstituted depend upon the morphology which develops during freezing and upon solvent sublimation. In this paper, the use of an environmental scanning electron microscope (ESEM) with a cryostage attachment is reported as a means of studying such structural evolution during the sublimation process. Results indicate that cryo-ESEM can provide a useful addition to techniques already used for the development of freeze-drying cycles, such as differential scanning calorimetry and light microscopy.