Development of a microwave moisture sensor for application in the food industry

Abstract

The basic development of a contactless optionally density-independent and continuously operating on-line microwave moisture sensor for organic bulk materials is presented. Moisture determination by means of microwave power is volumetric, but for process control, quality preservation etc. the water content in weight percentage is recommended. Therefore, density and structure parameters, as well as dielectric properties, of different organic bulk materials with characteristic particle shape are measured and compared under different moisture content. Due to cellular tissues and organic compounds, structural behaviour depends very much on moisture and temperature. Results from compression experiments show the possibility of keeping the bulk structure constant within a wide range of water content. Consequently, microwave moisture measurement could be density-independent. A first calculation model shows the correlation between structure properties and the dielectric constant. ©1996 Academic Press Limited.