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United States Department of Agriculture

Agricultural Research Service

Research Project: SENSING MOISTURE CONTENT AND QUALITY OF GRAIN AND OTHER AGRICULTURAL PRODUCTS BY DIELECTRIC PROPERTIES

Location: Quality and Safety Assessment Research Unit

Title: Dielectric properties of agricultural products and applications

Authors
item Nelson, Stuart
item Trabelsi, Samir

Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: April 28, 2009
Publication Date: June 21, 2009
Citation: Nelson, S.O., Trabelsi, S. 2009. Dielectric properties of agricultural products and applications. ASABE Annual International Meeting.

Interpretive Summary: Dielectric properties of materials are electrical properties that determine how materials interact with electric fields such as those of high-frequency and microwave electromagnetic energy. Therefore, the dielectric properties of materials determine how rapidly they will heat in microwave ovens and lower radio-frequency dielectric heating equipment. Dielectric properties are also important in low power applications, such as their use in the rapid measurement of moisture content in grain and other commodities. Electronic moisture meters use radio-frequency electric fields to sense moisture content in products such as grain, because the dielectric properties are highly correlated with the moisture content of the grain. This review paper describes those applications of dielectric properties in agriculture, providing some history of the interest in dielectric properties of grain and seed. It presents graphically the dielectric properties of grain, insects, fruits, vegetables, and poultry products, obtained over wide ranges of frequency and temperature and describes the application of dielectric properties information for a few uses in agriculture. These applications include moisture measurement in grain, possible control of stored-grain insects through selective dielectric heating of the insects, and possible use of dielectric properties for sensing quality in fruits and other products. The information presented may interest engineers in developing instruments that could provide important tools for improving agricultural production, product and quality preservation, and marketing of agricultural products for the benefit of growers, processors and consumers.

Technical Abstract: The use of dielectric properties of agricultural products for sensing moisture in grain and seed and their application in radio-frequency and microwave dielectric heating is discussed briefly. Values for the dielectric properties of a number of products, including grain and seed, fruits and vegetables, and poultry products, are presented graphically to show the dependence of these properties on frequency, moisture content, and temperature. The potential for using the dielectric properties to sense quality factors other than moisture content is also considered.

Last Modified: 7/25/2014
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