Radio-frequency heating of foodstuff: Solution and validation of a mathematical model

Radio-frequency (RF) heating is based on the interaction between the electric field produced by the electrodes of a capacitor and the dipoles and ionic-charges contained within a food product. In this paper, the temperature profiles and, particularly, the non-uniformity of temperature distribution occurring during RF heating of cylindrical meat batters, were analysed by mathematical modelling of both electromagnetic and thermal phenomena. Meat batters were chosen as sample food, with dielectric and physical property data available as a function of temperature. Temperature profiles were experimentally measured along the sample axes, for RF output powers of 100, 200, 300 and 400 W, while electromagnetic and heat equations were simultaneously solved by means of the finite element software FEMLAB. The goodness of fit of the model was evaluated by comparing numerical results with measured temperature profiles. Results showed different heating rates within the samples and, therefore, an uneven temperature distribution. The closer the temperature measurement point was to the bottom of the sample, the higher was the heating velocity. Unevenness of temperature distribution was emphasised by the applied RF output power: the higher the applied power the more uneven was the temperature distribution.