Moisture determination in single peanut pods by complex RF impedance measurement

An assessment was made of estimating the moisture content (mc) of single peanut pods (in-shell peanuts) by measuring the complex impedance of a parallel-plate capacitor with a single pod between the plates. Capacitance (C), phase angle (θ) and/or dissipation factor (D) were measured at 1.0 and 5.0 MHz, and the measured values at these two frequencies were used in a derived empirical equation to calculate the mc. Previous research had determined that the mc of single and small samples of shelled peanuts (kernels) could be determined by similar measurements at 1 and 4.5 MHz. In this paper, the mc of the pods tested was between 5% and 25%. The predicted mc of the pods was within 1% of the standard air-oven values for about 85% of the single pods.