Dielectric analysis of food polysaccharides in aqueous solution

Abstract

The dielectric properties of typical ionic food polysaccharides, alginate and κ-carrageenan, were investigated in the frequency range from 10 3 Hz to 10 7 Hz. For both polymers, two kinds of dielectric relaxation processes were observed; the higher-frequency relaxation being analyzed. The concentration dependence of the dielectric increment, Δε H, and that of the relaxation time, τ H, agreed well with the scaling law derived from polyelectrolyte solution theory. This result indicates that the mechanism of the high-frequency relaxation is ascribed to fluctuation of the loosely bound counterions to the polyelectrolyte within the range of the correlation length, ξ. Using the dielectric relaxation data, the crossover concentration from the dilute to the semi-dilute region for polysaccharide solutions was estimated. In addition, the fluctuation length of the bound counterions, d, and the concentration of counterions bound to the polyelectrolytes, N b, were evaluated. The dielectric relaxation measurement was an effective method for analyzing the polymer chain distribution and the counterion binding nature in the polysaccharide solutions. The dielectric relaxation of typical ionic food polysaccharides, alginate and κ-carrageenan, were investigated in the frequency range from 10 3 Hz to 10 7 Hz. The concentration dependence of the dielectric increment and that of the relaxation time agreed well with the scaling law derived from the polyelectrolyte solution theory, the relaxation being ascribed to the fluctuation of the loosely bound counterions to the polyelectrolyte.