MOISTURE AND TEMPERATURE-DEPENDENCE OF THE PERMITTIVITIES OF SOME HYDROCOLLOIDS AT 2.45-GHZ

The permittivities, i.e., dielectric constants and loss factors, of five powdered hydrocolloids were measured at 2.45 GHz at different moisture contents over the temperature range from 20-degrees-C to 100-degrees-C. The hydrocolloids were potato starch, locust bean gum, gum arabic, carrageenan, and carboxymethyl-cellulose. The moisture ranges were those of equilibrium moisture contents when sublots were conditioned at 25-degrees-C at known relative humidities up to 80 percent. Permittivities of all materials increased with moisture content and with temperature. The degree of temperature dependence of all five hydrocolloids increased as moisture content increased, but to a lesser degree in potato starch and to a much lesser degree in locust bean gum than in the other three. Dielectric constant and loss factor values are presented graphically for all five materials.