Computer simulation model development and validation for radio frequency (RF) heating of dry food materials

Radio frequency (RF) heat treatment has been identified as a novel pasteurization and non-chemical quarantine method for dry food materials. But the major obstacle of this treatment is non-uniform heating in these food materials. The objective of this study was to help understand RF heating process by developing a computer simulation model. A finite element based commercial software FEMLAB was used to develop the computer model for a 12 kW, 27.12 MHz parallel plate RF system. Wheat flour was selected as a model food to represent dry food materials. Dielectric properties of wheat flour were measured using an open-ended coaxial probe connected with impedance analyzer, whereas thermal properties were determined using a duel needle probe method. Simulated and experimented temperature profiles (°C) of wheat flour were compared in four different horizontal layers after 3 min of RF heating, with a fixed electrode gap of 155 mm. Both, simulated and experimental results showed that temperature values were higher at the mid layers followed by top and bottom layers. Corners were more heated than centers in each layer. Sensitivity analysis showed that temperature uniformity in the sample was most affected by top electrode voltage and sample dielectric properties. The developed model can further be used to study the effect of some important parameters such as sample size, position, shape, and dielectric properties on RF heating of dry food materials.