Microwave Permittivities Of Cracker Dough, Starch and Gluten

Abstract

An open-ended coaxial probe technique was used to measure the real and imaginary dielectric components of wheat starch, wheat gluten, and a commercial cracker dough. The permittivity or dielectric constant (e) and the dielectric loss (e“) or loss factor were determined as a function of moisture and frequency at constant density and temperature. The permittivity was measured over a continuous frequency range from 0.2 GHz to 20 GHz. The moisture range is 20% to 40%, typical of a normally processable dough. Two discrete areas of dispersion are observed at moisture contents above 30% correlating with the appearance of free water in the material, as measured by differential scanning calorimetry (DSC). The static (eS) and optical (e∞) dielectric constants for associated water are predicted. The semicircular plot thus obtained is consistent with the Debye model for predicting dielectric behavior of polar substances. eS and e∞ found to increase with increasing moisture content for starch, gluten, and cracker doug...