ABSTRACT
At present, conventional retorting that relies on saturated steam or pressurized hot water as sources of thermal energy is generally used in commercial production of low-acid (pH >4.6) shelf-stable packaged foods. With this method, the heat transfer in solid and semisolid foods is governed by slow conduction heating, resulting in severe overheating at the periphery of food containers. Dielectric heating, including microwave and radio-frequency (RF) energy, generates heat volumetrically throughout a food product rather than relying on the heat conduction, and thus offers the potential for quickly heating solid and semisolid foods. The much shorter heating times can potentially reduce quality (color and texture) degradation of sterilized foods. Electromagnetic waves at RF frequencies have longer wavelengths than those of microwaves; thus, RF power can penetrate further into most foods. Thermal processing based on RF energy can therefore be more suitable for large food trays such as 6-lb-capacity combat rations polymeric trays. Although RF heating holds potential for use in food sterilization, information about the sterilizing effects of RF heating as well as the control of RF heating systems is needed before RF heating can be considered for use in commercial
15.1 Introduction ........................................................................................................................ 259 15.2 Principles of Dielectric Heating .........................................................................................260 15.3 Dielectric Heating System .................................................................................................. 262 15.4 High Temperatures and Microorganisms ........................................................................... 262 15.5 Dielectric Heating and Microorganisms............................................................................. 263 15.6 History of RF Heating ........................................................................................................265 15.7 Current Status of Microwave Sterilization .........................................................................266 15.8 Important Considerations in FDA Applications .................................................................266 15.9 Food Sterilization Processes ............................................................................................... 267 15.10 Process Design Considerations Based on RF Heating ....................................................... 267 15.11 Identication of Cold Spots in RF Heating ........................................................................268 15.12 Microbial Validation of RF Sterilization Processes ...........................................................268 15.13 Food Quality of RF Sterilization ........................................................................................ 270 15.14 Critical Control Points of the WSU RF Heating System .................................................... 271 15.15 Challenges for FDA Filing of RF Heating ......................................................................... 274 15.16 Conclusions ......................................................................................................................... 275 Acknowledgments .......................................................................................................................... 275 References ...................................................................................................................................... 275
packaged food processing. This review will provide an update on the current status of research on RF sterilization for shelf-stable packaged foods.
