ESTIMATION OF TEMPERATURE PROFILE AT OHMI C HEATING BY FINITE-ELEMENTMETHOD

The heating process of foods, in general, depends on the heat transfer such as heat conduction, heat convection and thermal radiation that a re derived by the temperature difference between foods and that source s. The homogeneous and quick heating of foods is not expectable for th ese heat transfers because of the poor heat transfer coefficient of fo ods and the avoidance of overcooking on the food surface. On the other hand, the Ohmic heating will depend its heating on the generated heat when the electricity passes through the foods. According to its princ iple, the homogeneity of foods will result in the homogeneous and quic k heating. However, it is often observed that a homogeneous paste food such as ''Miso'', fermented soybean food, show the bigger temperature deviation than expected between its center and outer surface even und er the consideration of its heat diffusion. In this paper, Mise was us ed and measured its temperature change at 5 mm intervals from the cent er to the surface during the Ohmic heating at 20 kHz of alternating cu rrent. Finite Element Method (FEM) was examined to the mathematical co rresponding model to the obtained temperature changes. The model that the electric conductance of Mise was changeable depending on the tempe rature and the voltage drop was changeable depending on the electric c onductance showed good agreement with the actual result of temperature changes. The model also indicated that the crosswise temperature chan ge of Mise to the applied electrical field, was enhanced and the longw ise one was suppressed as its Ohmic heating progressed. The model will be very effective to design the electrode for Ohmic heating to achiev e the real homogeneous and quick heating of foods.