Characterization of frozen glucose solutions.

Reducing sugars may be used as additives in freeze-dried formulations. The purpose of this study is to examine the effect of freezing on nonequilibrated glucose solutions using FT-Raman spectroscopy. The methods used solutions freshly prepared from either alpha- or beta-crystalline glucose, frozen at different time intervals after dissolution. Solutions frozen immediately after dissolution showed peaks in the anomeric region of the spectrum characteristic of those observed for the parent crystalline form. No change occurred in these spectra after 24 hr in the frozen state. Solutions prepared from either alpha- or beta-crystalline glucose and left for 24 hr at room temperature before freezing showed the presence of both anomers. The glass transition temperature of maximally freeze-concentrated solutions of beta-glucose, frozen immediately after dissolution, was found to be approximately 3 degrees C lower than for solutions prepared from alpha-glucose. Freezing appears to halt the interconversion of glucose anomers, enabling the formation of predominantly alpha- or beta-frozen solutions which exhibit different properties. Freezing of nonequilibrated solutions of reducing sugars may lead to variation in the properties of freeze-dried formulations.