Submitted to: Innovative Food Science and Emerging Technologies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2002
Publication Date: 2/6/2002
Citation: Geveke, D.J., Kozempel, M.F., Scullen, O.J., Brunkhorst, C. Radio frequency energy effects on microorganisms in foods. Innovative Food Science and Emerging Technologies. 2002. V. 3. P. 133-138. Interpretive Summary: We studied the effects of radio frequency (RF) energy on microorganisms in liquid foods. If RF energy could destroy microorganisms with little or no heating, it may be possible to develop a process to pasteurize temperature sensitive foods and preserve their unique functional properties and flavor. Apple cider, beer, deionized water, liquid whole egg, and tomato juice containing Escherichia coli K-12, Listeria innocua, and yeast were studied Operating at a frequency of 18 MHz, our RF processor applied an electric field strength of about 0.5 kV/cm to the foods. The foods were processed in a range from room temperature up to the inactivation temperatures of the microorganisms. For comparison, the foods were also processed using a conventional method, indirect heating using hot water. Neither nonthermal nor synergistic effects of RF energy were detected. However, under different conditions, these effects may be possible. Although potentially difficult to achieve, the application of much higher field strengths may hold the key to obtaining these effects. If successful, industry and the public will benefit with safe, yet much higher quality liquid foods.
Technical Abstract: Liquids were exposed to radio frequency (RF) energy in order to study nonthermal effects on the inactivation of microorganisms. RF energy was applied to the liquids while thermal energy was simultaneously removed to control temperature. Turbulent flow was maintained to minimize localized heating. A 19 kW, 18 MHz, RF processor applied an approximate 0.5 kV/cm electric field strength to the liquids. There were no nonthermal effects of RF energy on Escherichia coli K-12, Listeria innocua, and yeast in apple cider, beer, deionized water, liquid whole egg, and tomato juice; nor were there any synergistic effects of RF energy with thermal energy at the inactivation temperatures of the microorganisms. However, the use of much higher field strengths or lower frequencies may hold the potential to inactivate microorganisms.