Journal of Microwave Power and Electromagnetic Energy (JMPEE)
TITLE	Microwave Permittivities of Cracker Dough, Starch and Gluten [PDF]
AUTHORS	L.C. Haynes and J.P. Locke 1995 30 2 124-131
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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 (ε') and the dielectric loss (ε'') 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 and optical 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. and were found to increase with increasing moisture content for starch, gluten, and cracker dough. This result is consistent with a shift of the relaxation time of bound water to higher frequencies. This is expected due to the greater mobility of the mixture with increasing amount of water as a plasticizer. Key Words: Dielectric, Permittivity, Dough, Starch, Gluten, Moisture