Finite element modeling of heat and mass transfer, and related nutrient change and microbial activity during microwave heating of food materials

A three-dimensional finite element model (FEM) was developed to predict temperature distribution, moisture distribution, nutrient retention and microbial destruction in food materials during microwave heating. The FEM was tested with analytical solutions and commercial software (TWODEPEP, ANSYS) calculated values. The FEM predictions compared favorably with analytical solutions (within 0.066% of maximum temperature) and values calculated from commercial softwares (within 0.14% of maximum temperature). The FEM was also verified using experimental data from microwave oven heated cylinder- and slab-shaped potato specimens. The FEM predicted temperature in potato samples agreed with measured results. The absolute maximum difference for slab geometry after 60 seconds of heating was 6.2;Two experimental devices, open column and capped column, were designed and built to determine four coefficients in the simultaneous heat and mass transfer equations. Three food materials, i.e., potato, bread dough and bread, were tested. Temperature gradient induced moisture migration coefficient was higher for low density materials (such as bread) than for high density materials (such as potato). Thermal conductivity and moisture diffusivity values obtained from this study for the three materials were comparable to the published data. The effect of temperature gradient on moisture migration in potato and bread during short time microwave heating of one-minute followed by three-minute holding time was found to be negligible, although the percentage contributed by the temperature gradient coefficient was large (114.6%) for bread.