Measurement of the Complex Permittivity of Food Products during Microwave Power Heating Cycles

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Abstract
A single mode active cavity (SMAC) perturbation technique operating with high level microwave power has been developed to heat and measure, at the same time, the permittivity of sample materials at 2.2 GHz. The accuracy of the SMAC measurement technique is compared with a series of permittivity measurements made on a number of identical liquid dielectrics using time domain spectroscopy (TDS) techniques. It is found that SMAC microwave power heat cycles on food products produced temperature permittivity hysteresis effects. Such hysteresis effects were previously observed on materials heated inside microwave ovens. A more complete characterization of the microwave heating hysteresis effect for food products may be of some interest in microwave food processing.