DIELECTRIC-PROPERTIES OF AGRICULTURAL PRODUCTS - MEASUREMENTS AND APPLICATIONS

Historical interest in dielectric properties of agricultural products and definitions of dielectric terms are presented briefly. The nature of dielectric properties variation with frequency, temperature, and product density is discussed. Techniques for measurement of dielectric properties are briefly reviewed, and graphical data on the dielectric properties of products are presented that illustrate the dependence of these properties on moisture content, frequency, temperature, and density. Models for estimating the dielectric properties of grain and soybeans as functions of moisture content, frequency, temperature, and bulk density are presented. Finally, applications of the dielectric properties of agricultural products are described that include radio-frequency (rf) and microwave heating for seed treatment, improvement of nutritional and keeping qualities of some products, and controlling insects in grain. Uses of dielectric properties for product quality measurement and the rapid determination of moisture content are described. Principles of moisture determination in single kernels and seeds and in bulk grain by rf and microwave measurements are briefly presented.