Dielectric Properties of Commercial Cooking Oils

Abstract

SUMMARY— The finished drying of potato chips represents the first large‐scale use of microwaves in the food industry on a continuous basis. Hence it was deemed desirable to study the dielectric properties of various types of commercial cooking oils.The dielectric constant (ɛ), and loss tangent (tans) of 11 commercial fats and oils have been determined at three different temperatures and at three different frequencies in the microwave range. The differences in dielectric properties among these fats and oils appear to be attributable to the phase (solid vs. liquid) of the material and generally correspond to the degree of unsaturation as evidenced by iodine values. The differences in loss factors among these fats and oils at any given temperature and frequency (within the range at which the measurements were made) are too small to be of any practical importance in selecting any one of them for use in heating processes using microwaves or in choosing an optimal frequency (300, 1000 or 3000 megahertz, MHz).Data for one of the oils (number 9) were obtained over a wider range of frequencies and indicate that the loss factor peak(s) is/are found in the frequency range of 100 to 1000 MHz. Furthermore, from the data obtained for the other oils, it should be safe to assume that this oil is representative of dielectric properties of the entire group. The dielectric properties of bacon fat rendered by microwaves are almost identical to those of bacon fat rendered by conventional means.