Dielectric properties of egg components and microwave heating for in-shell pasteurization of eggs

In this study, microwave heating has been considered for in-shell egg pasteurization. In the first part, the effects of temperature (0-62 degrees C) and frequency (200 MHz to 10 GHz) on the dielectric properties of egg components were investigated. In the second part, individual egg components as well as intact in-shell eggs were brought to pasteurization temperature in a laboratory-scale microwave oven working at 2450 MHz using different (0.75, 1 and 2 W g(-1)) power densities and the heating curve was analyzed to determine heating time required for different power levels. Under the conditions studied, it was demonstrated that the albumen had higher dielectric properties and loss factors leading to its faster heating rate in a microwave environment than the yolk. This was corroborated by the microwave heating trials performed on individual components where albumen always heated up faster. Laboratory trials on microwave heating of in-shell eggs indicated that, on the contrary, the heating rates of both albumen and yolk were similar. Microwave heating appeared to have great potential for in-shell egg pasteurization. Models for calculating the epsilon' and epsilon '' at a given frequency and temperature for shell egg components were also presented. (C) 2007 Elsevier Ltd. All rights reserved.