Dielectric Properties of Potatoes and Potato Chips

SUMMARY— Dielectric properties (dielectric constant, ɛ'_r; loss tangent, tans; and dielectric loss factor, ɛ"_r) were determined for raw potatoes and for potato chips, using the precision slotted line technique. Measurements on raw potatoes were made at 77°F (25°C) and at frequencies of 300, 1,000, and 3,000 MHz (megahertz). Measurements on potato chips were made at three moisture levels; at 77°F (25°C), 125°F (51.6°C), and 180°F (82.2°0; and at frequencies of 300, 1,000, and 3,000 MHz. Moisture, total lipids, and nitrogen contents are reported for both the raw potatoes and the potato chips.
As would be expected from their high moisture content and the presence of various dissolved salts, the raw potatoes possess extremely high dielectric values.
Potato chips show a rapidly decreasing dielectric loss as moisture content is reduced; the loss values of the chips approach those of the oil used for frying them after moisture has been reduced to approximately 3% and the oil content has been increased accordingly.
For finish drying of potato chips, a frequency of 3,000 MHz will result in 3–4.5 times greater power production in the chips than will the use of a frequency of 1,000 MHz (in the moisture and temperature range at which the data were obtained). However, this difference in power production is due almost entirely to the difference in frequency since the difference in dielectric loss values at the two frequencies is quite small.