Determination of Peanut Pod and Kernel Moisture Contents by RF Impedance Measurements

Abstract

Moisture content (mc) of individual peanut kernels, Arachis hypogaea L., was earlier determined by measuring the complex impedance of a parallel-plate capacitor with a kernel held between the plates. The method was based on measuring the capacitance, dissipation factor, and/or phase angle of a parallel-plate capacitor with a single peanut between the plates at 1.0 and 4.5 MHz. These values were used in an empirical equation to calculate the mc of the kernels ranging between 5 and 15% moisture. The calculated mc values were within 1% of the air-oven values for 90% of the kernels tested and were independent of kernel size. In this present work similar impedance measurements were made at two frequencies, 1 and 5 MHz, on single peanut pods as well as on each of the kernels taken out of the pods. Two empirical equations were developed, one for estimating the mc in single pods and the other for single kernels. The mc values thus obtained were compared with the values obtained by the standard oven method in each case and agreed well enough for practical use.