Dielectric Spectroscopy of Melons for Potential Quality Sensing

Abstract

Several cultivars of cantaloupe, honeydew melons, and watermelons were planted and harvested with a range of maturities for dielectric properties measurements and moisture and soluble solids content (SSC) determination. Permittivities (dielectric constants and dielectric loss factors) were determined over the frequency range from 200 MHz to 20 GHz with an open-ended coaxial-line probe and network analyzer for both interior tissue and surface measurements. Permittivity data are presented graphically for all three types of melons. High correlations were noted between SSC and moisture content in the tissues of all three kinds of melons, with SSC increasing linearly with decreasing moisture content of the edible tissues. Dielectric properties determined by measurements on the external surface of the melons had lower values than those of the internal tissues. Dielectric properties were similar for all three melon types, and they reflect the influence of the dielectric behavior of free water. No obvious correlations were noted between the dielectric properties and the SSC (sweetness) for sensing the quality of the melons.