ARS | Publication request: Microwave moisture sensor for rapid and nondestructive grading of peanuts

Submitted to: Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 1, 2010
Publication Date: March 18, 2010
Citation: Trabelsi, S., Nelson, S.O. 2010. Microwave moisture sensor for rapid and nondestructive grading of peanuts. IEEE Southeast Conference 2010.

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 10.5 percent, they cannot be sold in the United States. Microwave dielectric properties of peanuts are being studied for use in development of microwave moisture meters for use in the peanut industry. In particular, the microwave measurement technique provides a method for reliably measuring the moisture content of the peanut kernels from measurements on the unshelled peanut pods. This paper describes a low-cost microwave moisture sensor for rapidly and nondestructively determining the kernel moisture from measurements on peanut pods. 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, 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: A low-cost microwave moisture sensor operating at a single frequency for instantaneous and nondestructive determination of moisture content in peanut kernels from microwave dielectric measurements on peanut pods was developed and tested. The sensor operates at a frequency of 5.8 GHz and uses the principle of free-space transmission measurement of the dielectric properties. Moisture content is determined independent of bulk density with a permittivity-based algorithm.