Historical development of grain moisture measurement and other food quality sensing through electrical properties

Abstract

When the electrical properties of materials are well correlated with other properties or characteristics of those materials that are important, it is often possible to use properly designed instruments for rapidly measuring those nonelectrical properties of interest. This may be accomplished by the use of electric fields in sensing the electrical properties of the material and then obtaining estimates of the nonelectrical properties through appropriate correlations. In the agricultural and food industries, these kinds of measurements have been used for many years for rapid determination of moisture content in grain and seed. Research has been conducted seeking useful correlations between quality attributes of other food materials and their electrical properties, but they have generally been less successful than the determination of moisture content. In this article, an overview of the historical development of such measurement methods and techniques is presented with respect to grain and seed and other agricultural products and food materials. The article covers use of electrical resistance or conductance of grain samples, radio-frequency capacitance measurements, and microwave measurements of dielectric properties for sensing the moisture content of grain and seed. It deals with the principles involved rather than descriptions of specific instruments that have been developed for rapid measurement of grain and seed moisture content.