Dielectric Characterization of Fruit Nectars at Low RF Frequencies

Dielectric properties of apple, apricot, peach, and pear nectars were studied in the frequency range from 15 kHz to 30 MHz and the temperature range from 25 to 60°C. Both the relative dielectric constants and the dielectric loss factors decreased by increasing frequency and increased linearly with increasing temperature with values in the order 104–102 and 105–102, respectively. The power dissipation densities and the power penetration depths were found to increase linearly with temperature. Power dissipation densities remained essentially constant for all the samples while power penetration depths decreased significantly on increasing frequency. The dependence of each of the two dielectric properties on frequency and temperature has been described by two simple equations that proved to be adequate to describe the trend of the relative dielectric constant and dielectric loss factor for all the frequencies temperatures considered. It has been established that the dominant mechanism for the dielectric loss is ionic conductivity.