Nondestructive Moisture Content Determination of In-Shell Peanuts Using a Dual Frequency Impedance Meter

Abstract

Moisture content (MC) of in-shell peanuts was determined earlier from the impedance and phase angle measurements, made with a commercial impedance meter, on samples held between two parallel-plate electrodes. In this work, a dual frequency impedance meter and a parallel-plate electrode system was designed and used for these measurements at two frequencies 1 and 5 MHz. An empirical equation was developed from the measured values of impedance and phase angle of several calibration samples of in-shell peanuts, harvested during 2006, of known MC values ranging from 6% to 23%. From this equation, the MC of in-shell peanut samples within this moisture range harvested during 2005, 2006 and 2007 were determined and compared with their air-oven values. The sample size was about 100g. For over 94% of the samples tested from these three years, the MC values were found to be with-in 1% of the air-oven values. A commercial instrument developed on these lines will be useful in the peanut industry for rapid and nondestructive determination of MC of peanuts.