A fryer (100) generates electromagnetic waves betweena pair of opposed plate antennas (102) to control waterthat is an ingredient in food, specifically, a wateractivity of an object. The fryer (100) then applies a DCelectric field of +100 V as an offset electric field onthe water phase side relative to the oil phase in an ACelectric field to irradiate the food with electromagneticwaves at a frequency of 50 kHz. Thus, the interfacialpolarization between the water phase and the oil phase canbe increased to decrease the interfacial tension betweenthe water phase and the oil phase by approximately 60% andbind water in a pearl-chain structure, thus decreasing thewater activity.
