Location: Peanut Research
Title: Moisture Content Determination of in-Shell Peanuts Using a Low Cost Impedance Analyzer and Capacitor Sensor Authors
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 15, 2008
Publication Date: August 14, 2008
Citation: Kandala, C., Butts, C.L., Lamb, M.C. 2008. MOISTURE CONTENT DETERMINATION OF IN-SHELL PEANUTS USING A LOW COST IMPEDANCE ANALYZER AND CAPACITOR SENSOR. Transactions of the ASABE. 51(4):1377-1381. Interpretive Summary: Moisture content (mc) in peanuts is presently determined on bulk quantities, using capacitance type meters. For this the peanut samples are to be shelled and cleaned and placed in the sample holder of these meters for making a mc measurement. Cleaning and shelling of samples involves considerable time and labor. Also these samples, that are shelled and cleaned, are usually discarded after the mc measurement. Thus considerable quantities of edible peanuts may be lost during these tests. It will be useful if the mc of the peanuts could be determined by making physical measurements on the in-shell peanuts itself. In this work a parallel-plate capacitor system fitted inside a non-conducting cylindrical tube that measures the mc of in-shell peanuts in conjunction with a low cost impedance meter is described. The system was initially calibrated using peanut pod samples of known mc values in the moisture range of 6 to 23% from the 2006 harvest. The calibration constants generated were used in a semi-empirical equation developed, and the mc of peanut pod samples harvested during two consecutive years 2006 and 2007were calculated using the measured impedance values at the frequencies of 1 and 5 MHz. The calculated mc values of these samples were compared with the mc values of the samples obtained by the standard air-oven method and were found to be within 1% of the air-oven values for over 90% of the samples tested from both the years. This method is rapid and nondestructive and performs well with the same calibration constants for samples tested from two different years.
Technical Abstract: Moisture content (MC) in peanuts is an important parameter to be measured and monitored at various stages in peanut industry. In previous research, the peanut MC was estimated by placing a sample between a set of parallel-plate conductors and capacitance and phase angle of the system using commercially available and expensive impedance analyzers. In this work, a low-cost impedance analyzer called the CI meter was designed and developed to measure impedance and phase angles at frequencies 1, 5 and 9 MHz using the parallel-plate sensor. The average MC values predicted by the CI meter for peanut samples harvested during two different years were compared with the standard air-oven values. In-shell peanut sample MC ranged between 6% and 23%. Over 90% of estimated in-shell MC values were within 1% of the air-oven values. Ability to determine the average MC of in-shell peanuts without shelling and cleaning them can be of considerable use in the peanut industry.