Modeling dielectric properties of foods as a function of composition and temperature

The dielectric properties of turkey meat containing different concentrations of sodium lactate, glycerol and lactic acid, at water activities of 0.98–0.84 were measured at 2450 and 915MHz. Equations were developed as a function of temperature, moisture, water activity and ash, and compared to literature equations. Unexpected results were: as the water activity decreased or ash increased, the dielectric constant increased instead of decreasing with temperature, and dielectric loss factor of reduced moisture samples was determined by moisture not ash. It is theorized that the effect of temperature on dielectric constant is a function of the ratio of bound to free water. Glycerol did not affect the dielectric properties while lactic acid decreases them by promoting water loss during protein denaturation.; The dielectric properties of 19 different ham samples with different moisture (38.2–68.9%) and ash contents (1.78–6.80%) were measured at −35 to 70°C at 2450MHz. Equations were developed as a function of temperature, moisture, and ash, and compared to literature equations. The dielectric constant decreased with ash content and increased with moisture content. It increased instead of decreasing with temperature. The dielectric loss factor increased with moisture content for moisture contents lower than 60.7%, then decreased for higher moisture contents. Ash content and temperature increased dielectric loss factor. Frozen samples had low dielectric activity that was increased by ash content above −20 to −10°C.; The dielectric properties of fifteen vegetables and fruits were measured at 2450MHz from 5–130°C. Equations were developed as a function of temperature, moisture, water activity and ash, and compared to literature equations. Dielectric constant of vegetables and fruits decreased with temperature and ash content. However, ash was not a factor in the equations produced separately for fruits. Dielectric loss factor changed quadrically with temperature: first decreasing and then increasing. Transition temperatures decreased with ash content. Ash increased the dielectric loss factor. The dielectric constant, which gave a smaller average error, was better predicted than the dielectric loss factor. Modeling vegetables and fruits separately increased accuracy for both dielectric constant and dielectric loss factor.