Microwave Meter for Rapid, Nondestructive Determination of In-Shell Peanut Kernel Moisture Content from Dielectric Measurements on Cleaned and Uncleaned Pod Samples

Abstract

A microwave moisture meter built with off-the-shelf components was developed, calibrated and tested in the laboratory and in the field for nondestructive and instantaneous in-shell peanut kernel moisture content determination from dielectric measurements on cleaned and uncleaned pod samples. The meter operates at a single frequency of 5.8 GHz and uses free-space transmission measurement principles for determining the dielectric properties of the peanut pods. From these properties, a permittivity-based algorithm provides the bulk density and moisture content of the pods, and the kernel moisture content. Field tests showed that moisture content of peanut kernels can be determined while still in the pod with a standard error of performance (SEP) of 0.82% moisture content for dielectric measurements on cleaned pods and an SEP of 0.86% moisture content for uncleaned pods compared to the official meter. When compared to the oven-drying standard method, values of the SEP were 0.51% for the official meter and 0.31% for the microwave meter.