title: Water sorption and glass transition behaviors of freeze-dried sucrose-dextran mixtures.
abstract: 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.
authors.affiliation: Department of Bioscience and Biotechnology, Faculty of Engineering, Okayama University, Tsushima-naka, Okayama 700-8530, Japan.
authors.forename: Koreyoshi
authors.initials: K
authors.lastname: Imamura
authors.forename: Atsushi
authors.initials: A
authors.lastname: Fukushima
authors.forename: Keisuke
authors.initials: K
authors.lastname: Sakaura
authors.forename: Takuo
authors.initials: T
authors.lastname: Sugita
authors.forename: Takaharu
authors.initials: T
authors.lastname: Sakiyama
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Nakanishi
mesh_terms: D000327:Adsorption; D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D003911:Dextrans / Q000737:chemistry*; D005612:Freeze Drying; D008970:Molecular Weight; D013395:Sucrose / Q000737:chemistry*; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D003911:Dextrans; D014867:Water; D013395:Sucrose