HYDRATION AND DEHYDRATION OF CRYSTALLINE AND AMORPHOUS FORMS OF RAFFINOSE

The trisaccharide raffinose was prepared in its crystal pentahydrate, anhydrous methanolate, and amorphous forms and evaluated with regard t o dehydration and hydration properties at various temperatures and rel ative humidities. The pentahydrate, when stored at relative humidities (RHs) of <60% but >10%, showed no loss of water after 3 months of sto rage at 30 degrees C. When stored below 10% RH, only one water molecul e could be removed over a period of 3 months, whereas within 24 h at 3 0 degrees C in a vacuum oven, two water molecules were removed with no change in crystal structure. Increasing the temperature to 60 degrees C progressively removed the remaining three molecules, causing the cr ystal, however, to collapse into an amorphous form identical to one pr epared by lyophilization. Rehydration at 30 degrees C, which was suffi cient to reduce the glass transition temperature to <30 degrees C, rap idly restored the pentahydrate crystal structure. Rehydration of the m ethanolate also restored the pentahydrate structure. The significant a mount of water accommodated by raffinose in both the crystalline and a morphous forms would appear to make it a potentially useful water scav enger in certain types of dosage forms.