Dielectric investigation of the hydration mechanism in potato starch

The hydration mechanism of various polysaccharides of plant origin has been investigated by means of several physicochemical and dielectric techniques. In this work, we present, more particularly, results obtained with potato starch samples, using (a) equilibrium water sorption isotherms and (b) Thermally Stimulated Depolarization Currents (TSDC) techniques in the temperature range 77-300 K. The water content of our samples, defined as the ratio of weight of sorbed water to the weight of dry sample, varied between 2.4% and 41%. The results of equilibrium water sorption measurements were analyzed by fitting experimental data to the Guggenheim-Anderson-De Boer (GAB) equation. Two main relaxation regions are observed in TSDC spectra; the dependence of their characteristics on the water content is investigated and their origin is interpreted on the basis of results obtained in the first part of this work.