Sensing Moisture Content of Buckwheat Seed from Dielectric Properties

Abstract

<abstract><title><italic>Abstract.</italic></title> Dielectric properties (dielectric constant and dielectric loss factor) of static buckwheat seed were determined in the ranges of 1 to 1000 kHz for frequency of the electric field, 11.1% to 17.1% wet basis for moisture content, 722.1 to 800.6 kg m^-3 for bulk density, and 5°C to 40°C for temperature using a coaxial cylindrical capacitor. The influences of frequency, moisture content, bulk density, and temperature on the dielectric properties were investigated. Polynomials were developed describing the relationships between permittivities and moisture content, temperature, and bulk density at selected frequencies. The significance of each factor on the regression models was analyzed, and the accuracy of the models for calculating permittivites and for sensing moisture content was evaluated. The results showed that dielectric constant and loss factor both decreased with increasing frequency and increased with increasing moisture content, bulk density, and temperature. The second-order and third-order polynomials could be used to describe the relationships between permittivities and affecting factors at selected frequencies. Moisture content and temperature were significant factors influencing the dielectric properties of buckwheat. The regression models were verified to be accurate for calculating the dielectric constant and loss factor and for sensing moisture content from the obtained dielectric properties. This study offers useful information on dielectric properties of buckwheat and suggests that dielectric measurement can be used in sensing moisture content of buckwheat.