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Dielectric Properties and Radio Frequency Heating of Heterogeneous Foods

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  056038,  2005 ASAE Annual Meeting . (doi: 10.13031/2013.19555) @2005
Authors:   Kunchalee Luechapattanaporn, Yifen Wang, Jian Wang, Juming Tang, Linnea M. Hallberg
Keywords:   dielectric properties, penetration depth, radio frequency, microwave, sterilization, heterogeneous foods

Dielectric properties of major food ingredients (seasoned cooked ground beef, mozzarella cheese, noodles and sauce) in meat lasagna were determined using an open-ended coaxial line probe method at a range of 201 discrete frequencies between 1 and 1800 MHz and a range of temperature between 20 C to 121 C. Dielectric constants and loss factors increased as temperature increased at radio frequencies (RF) of 27 and 40 MHz, while these properties were relatively constant at microwave frequency of 915 MHz. Power penetration depths calculated from dielectric properties at 27 MHz for seasoned cooked ground beef (SCG beef), noodles and mozzarella cheese varied between 30 and 33 mm at 121 C. A slightly shorter penetration depth in sauce (21 mm) was found at 27 MHz and 121 C. Relatively uniform heating based on RF energy at 27 MHz was observed when SCG beef, mozzarella cheese and sauce were uniformly distributed between layers of noodles inside a 6-lb capacity combat group-ration polymeric tray. The greatest temperature differences when the product reached 121 C among different ingredients inside a tray at approximately the same location were within the range of 2 to 5 C. RF heating can reduce heatup time to one-third of that of retort heating. This study suggests that RF heating has a potential to produce pre-packaged heterogeneous food if major ingredients (SCG beef and noodles) have dielectric loss factors within the same range (1600-1800 at 27 MHz and 121 C).

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