Microwave dielectric method for the rapid, non-destructive determination of bulk density and moisture content of peanut hull pellets

• Dielectric properties of peanut hull pellets were measured in free space between 5 GHz and 15 GHz at 22 °C.
• Bulk density independent of moisture content and temperature from a modified Cole–Cole plot.
• Moisture content independent of bulk density with a permittivity-based calibration function.

A rapid dielectric-based method was used to non-destructively determine the moisture content and bulk density of peanut-hull pellets from free-space measurement of their dielectric properties at microwave frequencies. For moisture content determination, a permittivity-based function was used that permits moisture prediction independent of bulk density from measurement of the dielectric properties at microwave frequencies. For bulk density determination, an analytical expression was obtained from a representation of the dielectric properties in the complex plane. Results of moisture and density prediction from measurement of the dielectric properties are shown at 5, 10, and 15 GHz at 22 °C.