Dielectric constant and induced dipole moment of edible oils subjected to conventional heating

Abstract

The frequency dependence of the dielectric constant, the dielectric loss factor and conductivity were studied for five edible oils in the frequency range of 100 kHz to 13 MHz at different temperatures using frequency domain spectroscopy. The dielectric constant was similar for all the samples, in agreement with previous reports. The dielectric loss was low (<0.01), except for virgin olive oil with a value of 0.05. The dielectric loss peak frequency was 4 MHz for corn oil and around 5.2 MHz for the others. At this frequency, conductivity was on the order of 10-7-10-9 S/cm and decreased with temperature, following the behavior of dielectric losses. The refractive index, molar and orientation polarization were calculated for all types of oils using the novel theory proposed by N. M. Putintsev and D. N. Putintsev. The data show that orientation polarization contributes to the observed dielectric constant at low temperatures and frequencies. This indicates that edible oils are not pure non-polar dielectrics. The induced dipole moments of the oils were calculated for 400 kHz and 10 MHz at 300 K and 318 K. The results are discussed and correlated as a function of temperature and frequency to establish this relationship.