15D-29 |
Sterilization of a model food using radio frequency heating. |
Y. WANG1, T. D. Wig1, L. M. Hallberg2, and J. Tang1. (1) Department of Biological Systems Engineering, Washington State University, PO Box 646120, 213 LJ Smith Hall, Pullman, WA 99164-6120, (2) Advanced Processing and Packaging Team - Combat Feeding Program/ Soldier Systems Center, U.S. Army Soldier and Biological Chemical Command, Kansas St., Natick, MA 01760-5018 In the years since Prescott proposed using dielectric heating for pasteurization of milk in 1927, many studies of Radio Frequency (RF) heating in pasteurization and sterilization have been undertaken. Non-uniform temperatures within products and difficulty in the application of overpressure during RF heating stood as major barriers to developing this technology. In principle, RF has relatively long penetration depth (compared to microwaves) and can process institutional size food packages. It is desirable to develop novel thermal treatments that use RF energy to provide direct, rapid, and uniform heating in prepackaged foods to improve quality. The objective of this work was to develop a high-temperature short-time sterilization protocol for a model food using RF dielectric heating. A pressure vessel compatible with an RF heater was used to conduct sterilization studies using model foods in sealed packages. The formulation of the model food was adjusted to approximate the dielectric properties of selected food products. Real-time temperature data were collected with fiber-optic probes, and the cumulative heating effect was obtained by means of a chemical marker assay. In order to minimize edge heating, water immersion was used to improve the dielectric match between the package and its surroundings. The results indicated that satisfactory temperature uniformity and lethality Fo=12 min were achieved within a short process time (<30 minutes). As expected, no pronounced hotspots due to standing wave effects, often encountered at microwave frequencies, were observed. This process could lead to the production of shelf-stable foods with only minimal heat-induced product degradation. RF sterilization should offer a significant improvement for thermally processing institutional packaged food, which can suffer significant surface quality degradation due to prolonged heating cycles in conventional retorts.
Session 15D, Food Engineering: Processing Technologies
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