食品加工における過熱水蒸気利用に関する研究

Abstract

Heating of food products based on convective heat transfer from hot air to the food products is common in food processing operations, such as oven and drying process. Food is typically heated in humid air that contains a small amount of steam/water vapor. If the air contains a large amount of steam, steam could condense on the surface of the food, the dew point being higher than the temperature of the food. Moreover, when the temperature in the heating chamber is higher than the boiling point of water (100℃ ) at atmospheric pressure, the chamber space could become filled with pure steam with a temperature above the boiling point of water; this steam is called superheated steam. In this report, superheated steam and its utilization are described from the interdisciplinar y perspectives encompassing thermodynamics, mechanical engineering, and food engineering. A heat transfer model is proposed to investigate the steam condensation followed by condensate evaporation occurring in the initial stage of food heating. The effects of humidity on food drying using superheated steam and hightemperature air are investigated experimentally.