Dielectric analysis of sol-gel transition of κ-carrageenan with scaling concept

The dielectric properties of a typical ionic food polysaccharide, kappa-carrageenan, were investigated with special relevance to the sol-gel transition of its dispersed system. The dielectric relaxation around 1 MHz due to counterions bound to the polyelectrolyte was analyzed. For the disordered (coil) state of kappa-carrageenan solutions, dependence of the dielectric increment, Delta epsilon, and that of the relaxation time, tau, on the polymer concentration, C, were summarized as Delta epsilon proportional to C-0 and tau proportional to C-1, respectively, in good agreement with the scaling relations for the semidilute solutions derived from the polyelectrolyte solution theories. For the ordered (helix) state of kappa-carrageenan dispersed systems, the values of the dielectric parameters, Delta epsilon and tau, were larger than the predicted values using the scaling equations for the semidilute solutions. The deviation between the measured and predicted values can be understood as a result of the association of the helical conformers in gels.