The structure of water determined by microwave dielectric study on water mixtures with glucose, polysaccharides, and L-ascorbic acid

Abstract

Dielectric relaxation measurements over an extremely wide frequency region from 1 MHz to 20 GHz were performed on water mixtures with glucose, polysaccharides, and L-xylo ascorbic acid by the use of time domain reflectometry. For mixtures of polysaccharides bigger than maltotriose, two relaxation peaks were definitely observed. The high frequency relaxation is the water relaxation and the low frequency one is due to orientation of polysaccharide molecules. In the case of glucose, only one relaxation peak could be observed. It is shown that a hexagonal cluster in the lattice of ice can be replaced easily by the glucose molecule, where the lattice is distorted slightly, but stabilized by several hydrogen bonds between the glucose molecule and the lattice. Although the cluster can be replaced by the L-ascorbic acid molecule too, the lattice cannot be kept stable. Its water mixture shows two relaxation peaks clearly. It is suggested that water has a structure of the distorted lattice of ice. Fluctuation of the lattice breaks the hydrogen bonds and the lattice is decomposed. Orientation of the water molecules released gives rise to the relaxation concerned.