The dielectric loss mechanism of biological material during low temperature freezing

The dielectric loss property of some biological materials has been studied during freezing. Generally, biological materials have very high permittivity at room temperature and low frequency because of their high water content. During low temperature freezing, the permittivity changes suddenly from 10⁶ to 10² with a large proportion of water changing into ice. At the same time, the dielectric loss tangent (tgδ) increases and a peak appears. The temperature appearing peak is dependent on the composition of material and the content of water. The variation rate of permittivity and dielectric loss tangent with temperature can show the dimensions and quantity of the ice crystals in materials. Therefore, the relationship between dielectric spectrum and phase change, or dielectric spectrum and the metabolic rate of cells may be established, by means of studying the dielectric polarization and loss phenomena of biological materials in the course of the phase change at low temperature