Submitted to: ASAE Annual International Meeting
Publication Type: Abstract Only
Publication Acceptance Date: December 15, 2004
Publication Date: July 17, 2005
Citation: p.25, v.15 Interpretive Summary: Moisture content (mc) in peanuts (Arachis hypogaea L.) is an important function to be measured and monitored in their marketing and processing. Freshly dug peanuts may have a mc value as high as 40%. After digging the peanuts are usually allowed to dry on the vines for some time and this may bring down the mc value to about 20%. However after harvesting the peanuts must be dried to less than 10.5% for grading and sale (USDA, Update 2000). They can be stored at this moisture level when provided with adequate ventilation. Moisture content is presently measured with commercial moisture meters that measure average moisture content for samples that weigh about 200g. This average does not provide information on the range of moisture contents that may be present among individual kernels within the sample. A single kernel mc measuring instrument would be useful in detecting blending of high moisture peanuts with those at acceptable levels. In this article a portable electrical instrument that measures the complex impedance of a parallel-plate system for obtaining single peanut kernel mc is described. This instrument measures the complex impedance and phase angle of a parallel-plate capacitor system with a single peanut kernel held between them. These measured values were used in an empirical equation, earlier developed, to calculate the moisture content in single peanuts. The method is rapid and nondestructive and the instrument being portable can be used under field conditions.
Technical Abstract: RF impedance values of a parallel-plate capacitor with a single peanut kernel in between the plates was measured using a commercial Impedance Analyzer and from these values, it was found earlier that the moisture content (mc) of the peanut can be estimated. Capacitance, dissipation factor and /or phase angle were measured at the frequencies 1 and 4.5 MHz for each kernel and using these values in an empirical equation the mc of the single kernels was determined. The predicted values were within 1% of their oven values for over 95% of the kernels, in the moisture range from 5% to 15%. In this work the design of a low-cost portable electronic instrument that would measure the complex impedance values for this purpose is described.