Moisture loss as related to heating uniformity in microwave processing of solid foods

Moisture loss due to internal evaporation and its relationship to nonunifor mity of heating in microwave reheating of high moisture solid foods was stu died. A simple heat and mass transfer model was developed that excluded dif fusional limitations of moisture movement. Microwave absorption and some di electric and thermal properties were measured as input parameters to the mo del. Effect of varying microwave penetration with moisture level and temper ature was included. For smaller total moisture loss, typical for a reheatin g application, predictions of total moisture loss and temperatures matched well with experimental data. Most of the moisture loss occurred from the ed ges due to higher temperature at these locations. Uniformity of heating to achieve a given average temperature is the key variable controlling total m oisture loss. When starting from a frozen material, heating is much more no nuniform, leading to a greater moisture loss. As surface area increases for a given volume, uniformity of heating increases and the total moisture los s reduces. This simple model can be an effective tool in computer-aided opt imization of food products and processes.