Performance Comparison of RF Impedance and DC Conductance Measurements for Single Peanut Kernel Moisture Determination

Abstract

Two methods for rapidly determining the moisture content of single peanut kernels (Arachis hypogaea L.), were compared with a standard forced-air oven method to evaluate their performance. One method was based on estimating the moisture content from the measurement of capacitance and phase angle of a parallel-plate capacitor with a single peanut held between the plates. These measurements were made at two frequencies (1.0 and 4.5 MHz). The other method was a DC conductance measurement on a single peanut as it passed between two crushing-roller electrodes. This method is used in a commercial instrument presently available. Moisture content was determined by these two methods and by the standard oven method on 30 individual peanut kernels randomly selected from each of six sample lots with moisture contents ranging from 6% to 16%, wet basis. Moisture content measurements obtained using the capacitance and the conductance methods were in agreement with the standard oven values to an acceptable accuracy for over 80% of the samples tested. A distinct advantage of the capacitance method is that it is nondestructive.