Effect of foreign material in peanuts on in-shell nondestructive moisture sensing with a microwave moisture meter

Authors: Trabelsi, Samir; LEWIS, MICAH - University Of Georgia

Submitted to: American Society of Agricultural and Biological Engineers
Publication Type: Proceedings
Publication Acceptance Date: 6/29/2011
Publication Date: 8/7/2011
Citation: Trabelsi, S., Lewis, M. 2011. Effect of foreign material in peanuts on in-shell nondestructive moisture sensing with a microwave moisture meter. American Society of Agricultural and Biological Engineers. 2011 CDROM.

Interpretive Summary: Electrical characteristics, known as dielectric properties, of grain and oilseed are closely related to the amount of water that they contain. Consequently, instruments can be designed to sense these dielectric properties and be calibrated to read moisture content. Such instruments, called moisture meters, are widely used in the grain and seed trade for rapid determination of moisture content. Moisture content is especially important in the sale and storage of peanuts so that spoilage and development of toxins can be avoided. If kernel moisture contents of peanut lots exceed 10.49 percent, they cannot be sold and have to be dried before they can be reconsidered for sale. Research on microwave dielectric properties of peanuts has revealed that measurements at these higher frequencies can reliably measure the moisture content of the peanut kernels from measurements on the unshelled peanut pods. This paper describes experimental measurements with a microwave moisture meter comparing measurements on cleaned, unshelled peanut pods with those taken in the same way on uncleaned peanut pods with foreign material as they arrive at the peanut buying points from the farms. Results showed that peanut kernel moisture content can be measured on uncleaned pod samples with essentially the same accuracy as measurements on cleaned pod sample. At peanut buying points, samples go through a thorough grading process before the moisture content is determined, and at that time the decision is made as to whether the peanut lot can be sold. Thus, the new microwave moisture technique offers a real advantage in peanut grading operations, because moisture content can be determined at the beginning of the grading process on uncleaned samples, and if it is too high, the time and labor lost in grading those samples can be avoided. The new microwave moisture sensor offers promise for improving efficiencies of grading and processing as well as preventing losses due to spoilage and will be a useful tool for peanut farmers, handlers, and processors, thus providing safe and high quality products for consumers.

Technical Abstract: Effect of foreign material on peanut kernel moisture content prediction from microwave dielectric measurements on peanut pods was investigated. A low-cost microwave moisture meter operating at 5.8 GHz was calibrated in the laboratory with clean samples of pods and kernels. Resulting moisture calibration equations were used to predict kernel moisture content from measurement of the dielectric properties of clean and unclean peanut pod samples of different varieties and originating from different growing locations. The standard error of performance when comparing with kernel moisture obtained with the official moisture meter were 0.81% for moisture predictions from measurements on clean samples of pods and 0.88% for moisture predictions from measurements on unclean samples of pods.