Molecular Motion in Carbohydrate + Water Mixtures in the Liquid and Glassy States as Studied by Spin-probe ESR

Abstract

Publisher Summary The glass transition is the phenomenon in which a solid amorphous phase exhibits a discontinuous change in the specific heat on changing the temperature. Due to an extremely high viscosity, the translational mobility of molecules at temperatures below the glass transition temperature is virtually zero. Consequently, a food product in the glassy state would not be expected to decrease in quality during storage. It is therefore useful to study the molecular properties of glassy states in more detail. To this end, the techniques of conventional and saturation-transfer Electron Spin Resonance (ESR) have been employed to study the rotational mobility of spin probes above and below the glass transition temperature in several carbohydrate + water mixtures. This chapter discusses molecular motion in carbohydrate + water mixtures in the liquid and glassy states as studied by spin-probe ESR. It concludes that spin probe ESR is a suitable technique to obtain information about the existence of hydrogen bonds and the presence of cavities in highly concentrated carbohydrate systems and it may also sense the glass transition temperature.