Water sorption, glass transition, and freeze-concentrated glass-like transition properties of calcium maltobionate–maltose mixtures

• Published in: Journal of thermal analysis and calorimetry Vol. 135; no. 5; pp. 2775 - 2781
• Main Authors: Fukami, Ken, Takeuchi, Sayaka, Fukujyu, Tomoya, Hagura, Yoshio, Kawai, Kiyoshi
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.03.2019; Springer; Springer Nature B.V
• Subjects: Analytical Chemistry; Aqueous solutions; Caking; Calcium; Chemistry; Chemistry and Materials Science; Collapse; Crystallization; Disaccharides; Glass transition temperature; Inorganic Chemistry; Isotherms; Maltose; Measurement Science and Instrumentation; Moisture content; Physical Chemistry; Polymer Sciences; Sorption; Temperature; Water; Water activity; Glass transition; Calcium maltobionate; Maltose; Freeze-concentrated glass-like transition; Water sorption isotherm
• ISSN: 1388-6150; 1588-2926
• DOI: 10.1007/s10973-018-7793-7

The water sorption, glass transition, and freeze-concentrated thermal transition properties of calcium maltobionate (MBCa)–maltose mixtures were investigated. At lower maltose molar fractions, the water content of the mixtures increased sigmoidally with water activity ( a w ). At higher maltose molar fractions, maltose preferentially crystallized in an a w condition, and water sorption isotherms deviated from sigmoidal behavior. The glass transition temperature ( T g ) decreased with increasing water content because of a water-plasticizing effect, described as a T g curve. The critical water content ( W c ) and critical water activity ( a wc ) (i.e., water content and a w at T g  = 298 K) were determined from the water sorption isotherms and T g curves. The values of W c and a wc decreased linearly with increasing maltose molar fraction. The DSC curve of the MBCa–maltose aqueous solutions showed a large endothermic shift before the endothermic peak due to melting ice, and freeze-concentrated glass-like transition temperature ( T g ′) was evaluated from the endothermic shift. The T g ′ of the MBCa–maltose aqueous solutions decreased with increasing maltose molar fraction. These results are useful for predicting the physical stability (collapse, crystallization of maltose, and powder caking) of MBCa–maltose mixtures during freeze-drying and subsequent storage.