Dielectric properties of salmon fillets as a function of temperature and composition

Dielectric properties for anterior, middle, tail, and belly portions of Alaska pink salmon (Oncornynchus gorbuscha) fillets were measured at frequencies between 27 and 1800 MHz from 20 to 120 degrees C to provide insights for improving the modeling of microwave (MW) and radio frequency (RF) commercial sterilization processes of salmon products. Compositional differences contributed to the observed slight differences in the dielectric properties for different parts of salmon fillet. For all portions of the fillet, similar trends in dielectric constant and loss factor measurements were observed as a function of temperature (20-120 degrees C). At RF frequencies of 27 and 40 MHz, the dielectric constant decreased with increasing temperature. But at microwave frequencies (e.g., 915, 1800 MHz), an opposite trend was observed. The dielectric loss factor increased with increasing temperature over the tested frequency range. Calculations from electrical conductivity of minced salmon fillets measured at different temperatures suggest that ionic conductivity was the major contributor to temperature dependent behaviors of dielectric properties at RF frequencies. (c) 2007 Elsevier Ltd. All rights reserved.