17G-3 |
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J. WANG, Y. Wang, K. Luechapattanaporn, and J. Tang. Dept. of Biological Systems Engineering, Washington State Univ., PO Box 646120, Pullman, WA 99164-6120 Radio Frequency (RF) dielectric heating has been used in High Temperature Short Time (HTST) thermal processes for packaged foods. It takes the advantage of great heat penetration depth of radio frequency waves in food materials and can process large institutional sized food packages. In a RF heating system, the packaged food is heated by conversion of electromagnetic energy into thermal energy within the package, and thus the cold spot inside the food is determined by the distribution of the electromagnetic wave. Computer simulation is one of the best methods to determine the distribution of the electromagnetic field. The accuracy of the simulation result depends not only on the simulation software, but also on the accuracy of dielectric properties of the food been used. Our objective was to measure the dielectric properties of liquid whole eggs, solid whole eggs, liquid egg whites, and solid egg whites at frequencies of 27, 40, 915, and 1800 MHz over the temperature range from 20ºC to 121.1ºC. The open-ended coaxial probe method, which is commonly utilized to measuring liquid, semi-solid and solid materials, was used to test the dielectric properties of the several egg products. A custom-made dielectric property measuring system built at Washington State University was used in this study. Our results showed that the dielectric properties of the four tested egg products increased linearly with temperature. A cross point was observed in the graph of the dielectric properties when comparing the liquid whole eggs with the solid whole eggs; a similar phenomenon was also observed in comparison between liquid egg whites and solid egg whites. The measured dielectric properties will be used in computer simulation to study RF heating uniformity, which then will be of great helpful in finding the cold spot during RF heating processing, and in improving the RF heating uniformity.
Session 17G, Food Engineering: Physical, chemical and electrical properties
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