Predictive equations for the dielectric properties of foods

Abstract

Variations in the dielectric properties of foods with applied microwave frequencies, and food composition, moisture content and temperature, were investigated. A series of equations to estimate the dielectric properties of a wide range of food materials was deduced from available experimental data and current understanding. The equations are suitable for incorporating into a numerical model to predict the transient temperature and moisture-content profiles within microwave-heated foods.

Measurement techniques and application of electrical properties for nondestructive quality evaluation of foods—a review

“…Calay et al (1995), Nelson (2003) The ε′ increased with an increase in the moisture content and bulk density, whereas it decreased with an increase in the frequency. Sacilik et al (2007) Fresh eggs Freq.…”

“…The dielectric constant and loss factor of flaxseed increased with an increase in moisture content and bulk density and with a decrease in frequency (Sacilik et al 2006). The rate of change of dielectric constant and loss factor with temperature depends on the free and bound water content of the food materials (Calay et al 1995). The dielectric constant of fatty acids increased with an increase in the number of double bonds or molecular chain length.…”

“…Both the dielectric constant and loss factor of various foods increased with increasing moisture content . In general dielectric constant of fruits and vegetables increases with temperature, whereas loss factor may either increase or decrease depending on the operating frequency (Calay et al 1995). generally increased with increasing temperature (Nelson 2003;Sosa-Moralesa et al 2009) and dielectric constant increased with temperature at lower frequencies, but decreased with temperature at the higher frequencies and, temperature dependence of dielectric constant was minimal in the frequency range between 0.01 and 1.8 GHz (Nelson 2003).…”

Effect of Microwave Heating on Flavour Generation and Food Processing

“…The amount of heat generated in microwave heating depends upon the dielectric properties of the food and the loss factor (see below), which are affected by the food composition, the temperature and the frequency of the microwave energy. For tables of electrical properties of food, and discussion of their application Kent (1987), Ryynanen (1995), and Calay et al (1995).…”

Estudio de los espectros dieléctricos para el control de calidad de alimentos

“…Aplicación de la espectroscopia dieléctrica de microondas a productos de la agricultura Se ha estudiado la aplicación de microondas a diversas frutas y vegetales con la finalidad de correlacionar diferentes propiedades como son: humedad, contenido en almidón, y efecto de la temperatura con la variación de las propiedades dieléctricas (Nelson, 1980(Nelson, , 1983(Nelson, , 1992(Nelson, , 2005Tran et al, 1984;Seaman y Seals, 1991;Nelson et al, 1993Nelson et al, , 1994Berbert et al, 2002;Feng et al, 2002;Sharma y Prasad, 2002;Sipahioglu y Barringer, 2003;Datta et al, 2005;. Se han desarrollado varios modelos predictivos que correlacionan las propiedades dieléctricas de frutas y vegetales con algunos parámetros como la humedad, sólidos solubles e insolubles y temperatura (Sun et al, 1995;Tulasidas et al, 1995;Sharma y Prasad, 2002;Nelson, 2003;Sipahioglu y Barringer, 2003;Berbert et al, 2004;Calay et al, 2007). En general, cabe destacar que las frutas y verduras poseen una fase líquida importante que provoca que la constante dieléctrica adquiera valores altos; por el contrario, en frutas y verduras deshidratadas tanto la constante dieléctrica como el factor de pérdidas toman valores menores.…”