The Mechanism of Drying of Food Model by Microwave Energy and Flowing Air
Studies on Microwave Draft Drying Part I
1982 Volume 29 Issue 10 Pages 587-595
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1982 Volume 29 Issue 10 Pages 587-595
The mechanism of drying process of thick foods by microwave energy and flowing air was studied in this work. Piled wet papers (20mm thickness) were used as a food model and they were dried by flowing air with various temperatures, humidities and rates in microwave draft cavity. Their inner layer was maintained at prescribed temperature. throughout drying period by controlling microwave power. The results obtained were as follows. (1) Moisture distribution in the samples in microwave drying process much depends on the temperature difference ΔT between the temperature of their inner layer, Ti and the temperature of the flowing air, Ta (ΔT=Ti-Ta). When ΔT is less than 20°C, drying proceeds under the state where moisture content of inner layer Wi is more than that of outer one, Wo. However, when ΔT is higher than 30°C, it dose under the state where Wo>Wi. And when ΔT is approximately equal to 25°C, drying of the samples iS performed under the state where Wo≈Wi. From these results, it might be suggested that if we choose ΔT of adequate value, any kinds of foods may be dehydrated uniformly. (2) When the temperature of the flowing air is lower than that of the sample, drying rate are decreased in proportion to its flowing rate, since heat transduced from energy of microwave in the sample is removed significantly. (3) Humidity of the flowing air dose not effect so much on drying rate, distribution of moisture and temperature in the samples.
