DIELECTRIC-PROPERTIES OF GRAPES AND SUGAR SOLUTIONS AT 2.45 GHZ

Dielectric properties of grapes at 2.45 GHz were measured at moisture contents varying from 80 to 15% (wet basis) at temperatures ranging fr om 25-80 degrees C using the Open Ended Coaxial Transmission Line Tech nique. Both dielectric constant and loss factor decreased with decreas ing moisture content. In low moisture samples these properties were fo und to be considerably influenced by higher temperatures. Dielectric p roperties of sugar solutions of varying concentrations (20-250% by wei ght in water) were also determined at different temperatures, and thes e values were compared to those of grapes of corresponding moisture co ncentration. Predictive models of the dielectric properties as functio ns of moisture content and temperature were generated using response s urface methodology. The results are useful in estimating the volumetri c hearing of grapes by microwave energy, and these methods can be exte nded to sugar-based foods in general.