Water sorption and glass transition behaviors of freeze-dried sucrose–dextran mixtures

✍ Scribed by Koreyoshi Imamura; Atsushi Fukushima; Keisuke Sakaura; Takuo Sugita; Takaharu Sakiyama; Kazuhiro Nakanishi

• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: English
• Weight: 116 KB
• Volume: 91
• Category: Article
• ISSN: 0022-3549
• DOI: 10.1002/jps.10218

✦ Synopsis

The water sorption and glass transition behaviors of freeze-dried disaccharide-polysaccharide mixtures at various contents were investigated at relative humidities (RHs) of 0, 11, 23, and 33%. Sucrose and three types of dextrans, which differ in molecular weight, were used as model di- and polysaccharides, respectively. The relationship between the dextran and water contents of the sucrose-dextran mixture at different constant RHs indicated that a mixture of sucrose and dextran was lower than that calculated by the Lang and Steinberg mass balance equation. In the RH range of 0-23%, the glass transition temperature, T(g), increased to a considerable extent when the dextran content was equal to or higher than 50%, while the increase in T(g) at dextran contents lower than 50% was small. A marked increase in T(g) was observed at RH 33% for dextran contents of 0-25% as well as in the range above 50%. This suggests that the physical stability of the highly hydrated amorphous disaccharide is effectively strengthened by the addition of a small amount of polysaccharide. These tendencies were similar for the three dextrans of different molecular weights. Furthermore, it was demonstrated that the addition of a small amount of dextran is quite effective in preventing the collapse of amorphous sugar during freeze drying.