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Nondestructive moisture determination in small samples of peanuts by RF impedance measurement

Kandala, C.V.K., Nelson, S.O.
Transactions of the ASAE 2005 v.48 no.2 pp. 715
water content, peanuts, sampling, capacitance, impedance, nondestructive methods, food analysis
By using the measured RF impedance values of a parallel-plate system, with a single peanut kernel between the plates in an empirical equation, it was found in previous work that the moisture content of the peanut kernel could be closely estimated. This method was successfully applied to predict the moisture content of small samples of peanut kernels (6 to 8 kernels) but with a slightly modified empirical equation. Capacitance, dissipation factor, and/or phase angle were measured with an impedance analyzer and a parallel-plate capacitor with a small number of peanut kernels between the plates at two frequencies (1 and 5 MHz). Moisture contents were predicted within 1% of air-oven moisture determination values for 85% of the samples tested in the moisture content range from 6% to 22%. The method is rapid and nondestructive, and it could be used to develop a practical instrument to measure moisture content of peanuts. Such an instrument could be used to make moisture measurements on a large number of small samples from a bulk volume, to obtain a better estimate of the moisture distribution within the bulk volume, without destroying the samples. It could also be used in detecting blending of high-moisture peanuts with those at acceptable levels.