Physical Properties of Foods and the Effect of Water on Them II Electrical Properties and Dielectric Relaxation

Abstract

Dielectric spectroscopy has been widely used to study molecular dynamics in dispersed systems. With an increase in frequency, the dielectric constant, ε', often decreases, the electric conductivity σ' increases, and the dielectric loss, ε”, shows a peak, due to the delay in dipole moments, this phenomenon being the so-called dielectric relaxation. By fitting dielectric relaxation data to semiempirical equations, for example, the Cole-Cole equation, one can obtain a parameter reflecting the mobility of molecules, polymer chains and so forth, such as the relaxation time, τ, which corresponds to the time needed for electric dipoles to orient in the direction of an electric field. The application of the dielectric relaxation to food hydrocolloids such as BSA solution, gelatin solution, alginate solution, and so forth was reviewed. Each dielectric relaxation observed is considered to be ascribable to a different fluctuation or movement of “components” in the electric field among different hydrocolloid systems, thus giving information on the inner structure of the hydrocolloids. © 2008, Japan Society for Food Engineering. All rights reserved.