| A catering microwave oven was used to investigate the microwave heating of foodstuffs, The oven used for the experimental work, a Philips 1.2 kW model, operated at a frequency of 2450 MHz and the energy applicator was in the form of a resonant cavity. Heat generated in food in a microwave resonator is caused by an interaction between "lossy" components of the food and the electrical field of the microwave radiation. The heating effect depends upon the characteristics of both the resonator and the food. The experimental work was designed to investigate factors affecting this heating effect. The total power absorbed by food in a microwave oven is dependent upon its chemical composition and its geometry. It was found that power absorption increased with volume up to a maximum value, above which power absorption was independent of volume. Power absorption was also affected by the geometry of the food but it was not a function of the food's dielectric properties. Heat which is dissipated in the food, as a result of power absorption, is not uniformly distributed thr oughout the food. The distribution of heat in solid foods was investigated by measuring temperature profiles in slabs of agar after microwave heating; simple foodstuffs were also incorporated in the agar. In order to investigate factors which affect the temperature distribution in food, resulting from microwave heating, a computer simulation of microwave heating was developed. Good agreement was obtained between the measured and simulated profiles for agar slabs, although modifications to the simulation were required for actual foodstuffs. |
