Submitted to: Instrumentation and Measurement Technology Conference Record
Publication Type: Proceedings
Publication Acceptance Date: 3/23/2006
Publication Date: 5/24/2006
Citation: Trabelsi, S., Nelson, S.O. 2006. Nondestructive moisture sensing in peanut kernels from microwave permittivity measurements on unshelled pods. Proceedings of the 23rd IEEE Instrumentation and Measurement Technology Conference Record, May 24-27, 2006, Sorrento, Italy. pp. 305-307,CD.
Interpretive Summary: Dielectric properties of materials are those electrical characteristics that determine how they interact with electromagnetic fields. For example, some materials are heated much more rapidly in a microwave oven than others. Those materials that heat rapidly have a higher dielectric loss factor than materials that do not absorb much energy from the microwave fields. The dielectric properties of materials such as grain and oilseeds are also 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. Research has shown that microwave frequencies may offer advantages for the development of new moisture meters. Moisture content is especially important in the sale and storage of peanuts so that spoilage and development of toxins can be avoided. Microwave dielectric properties of both unshelled and shelled peanuts of different moisture contents were measured at different bulk densities, or packing densities, and results were analyzed for usefulness in rapidly sensing the moisture content of the peanuts. This paper reports details of the microwave measurements of the dielectric properties and reveals that moisture content is determined with accuracies of better than one half of one percent. In addition, it was determined that the moisture content of peanut kernels in the pods can be determined without need for shelling them. With further development, the microwave measurements offer good potential for saving considerable time and labor in the moisture testing required when drying peanuts and testing them for safe storage and marketing. Microwave moisture meters would be helpful in preventing losses due to spoilage and provide useful tools to peanut farmers, handlers, and processors, thus providing high quality products for consumers.
Technical Abstract: A method for moisture determination in peanut kernels from permittivity measurement at microwave frequencies on unshelled peanut pods is presented. The method is nondestructive and instantaneous. This method is particularly suitable for in-line routine measurement on large quantities of peanuts.