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Abstract
Permittivities, moisture
contents, tissue densities, and total soluble solids data were determined for
samples of twenty three kinds of fresh fruits and vegetables at 23°C. Permittivities were
measured at 41 frequencies between 200 MHz and 20 GHz with an open-ended
coaxial-line probe and a microwave network analyzer. Results of the
permittivity measurements are presented graphically, and dielectric constant
and loss factor values at six frequencies across the range are tabulated
along with sample descriptions and moisture, density, and total soluble
solids data. Although specific values differ, the dielectric constant
decreases steadily with increasing frequency, dropping more rapidly at
frequencies above 5 GHz. Values for the loss factor decrease as frequency
increases above 200 MHz to a broad minimum in the 1- to 3-GHz region and then
increase again as the frequency approaches 20 GHz. The dielectric behavior of
the fruit and vegetable tissues appears to be influenced by ionic
conductivity and bound water relaxations at the lower frequencies and by free
water relaxation at the higher end of the frequency range.
Key Words:
Fruits, Vegetables, Microwave
permittivity, Dielectric constant, Loss factor.
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