ABSTRACT
Osmotic dehydration can be used as an effective method to remove water from vegetable tissues while simultaneously introducing solutes in the product. Dielectric properties are of primary importance to evaluate the suitability and efficiency of microwave heating of the osmotically pretreated products. Furthermore, dielectric properties give insight in expected heat dissipation, temperature-time profiles, and heating homogeneity. The chapter aims to study the effect of dielectric properties on heating characteristics. It examines drying kinetics of the combined osmotic dehydration/microwave drying process. Measurement of the dielectric properties is performed with an open-ended coaxial probe connected with a network analyzer. The network analyzer detects the magnitude and phase shift of the reflected signal. With microwave drying, the dielectric properties are rapidly decreasing. The dielectric constant is decreasing as a result of the inclusion of air within the product and the loss factor is decreasing as a result of the loss of moisture.
