Mathematical modelling of microwave heating and thawing of solid foods

L. A. CAMPAÑONE, N. E. ZARITZKY

Rio de Janeiro, Brasil

Congreso; 2nd Mercosur Congress on Chemical Engineering,4th Mercosur Congress on Process Systems Engineering; 2005

The use of microwaves in the food industry is founded on the shorter times required to increase foodstuffs temperature when compared to conventional heating methods. However, there are some problems associated to temperature distribution within the products, owing to preferential absorption of electromagnetic energy by liquid water, caused by differences between its dielectric properties and those for ice (“runaway”). To analyze the behavior of food microwave heating,  a mathematical method was developed by solving the unsteady state heat and mass transfer differential equations. The model was applied to large systems for which Lambert´s law is valid because it leads to similar results as Maxwell equations. Thermal, transport (diffusional) and electromagnetic properties varying with temperature were used. The numerical solution was developed using an implicit finite difference method in one dimensional systems and an alternating direction method in two and three-dimensions. The model was validated with own data as well as with experimental data from literature. The computer program allows processes to be optimized to assess the effect of several operating conditions (external power, power cycles) and the influence of product geometry. In addition, the effect of various configurations (layers of fat and lean meat) on the internal temperature profiles was also tested.