Formation of a new crystalline form of anhydrous β-maltose by ethanol-mediated crystal transformation

β-Maltose monohydrate was transformed into an anhydrous form by ethanol-mediated method under several temperatures with agitation. A new stable anhydrous form of β-maltose (Mβs) was obtained, as substantiated by the X-ray diffraction patterns. Mβs obtained by this method presented a fine porous structure, resulting in greater specific surface area compared to those of β-maltose monohydrate and anhydrous β-maltose obtained by vacuum drying (Mβh). The crystal transformation presumably consisted of two steps: dehydration reaction from the hydrous to amorphous forms and crystal formation from the amorphous forms to the noble anhydrous form. The kinetics of these reactions were determined by thermal analysis using Jander’s equation and Arrhenius plots. The overall activation energies of the dehydration reaction and the formation of anhydrous maltose were evaluated to be 100 and 90 kJ/mol, respectively.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Crystal transformation of β-maltose monohydrate was investigated. ► Stable anhydrous β-maltose with new crystal structure was obtained in ethanol. ► SEM micrographs revealed a unique porous crystal structure with surface area. ► Kinetics and mechanism of the reaction were determined.