Electrical properties of vegetable oils between 20 Hz and 2 MHz

Abstract

Electrical properties (permittivity and conductivity) of vegetable oils were determined in the frequency range from 20 Hz to 2 MHz. Commercial samples of corn, sunflower, soybean, grapeseed, cottonseed, olive, canola and chia oils were measured at temperatures between 300 K and 343 K (stabilized within 0.1 K). The calibration uncertainty in the measuring system was below 1%. In all the measured samples the real part of the relative permittivity decreases with temperature, with a very good fit to a linear function; and it clearly depends on the oil source. The conductivity increases rapidly with temperature, fitting satisfactorily to an Arrhenius function. The values of the activation energy are between 0.34 eV (chia) and 0.46 eV (olive and soybean), and are consistent with previously reported values. These results are relevant for the application of electrical properties to the characterization of oils during transport and storage, and also to monitor the progress of the transesterification reaction.