Submitted to: Journal of Food Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/19/2016
Publication Date: 9/2/2016
Citation: Geveke, D.J., Bigley, A.B., Brunckhorst, C. 2017. Pasteurization of shell eggs using radio frequency heating. Journal of Food Engineering. 193:53-57.

Interpretive Summary: The USDA estimates that 110,000 illnesses could be prevented in the U.S. if all shell eggs were pasteurized. However, only 1% of eggs are currently pasteurized because the commercial, hot water process takes a very long time to complete. We invented a radio frequency (RF) apparatus and process that pasteurizes shell eggs in less than half the time. First, the eggs were heated using 60 MHz RF energy in 35.0 C water for 3.5 min. Finally, the eggs were heated for an additional 20 min with 56.7 C water. This two-step process reduced the population of E. coli in the shell eggs by more than 99.9999%. The total time for the process was 23.5 min. By contrast, processing for 60 min was required to reduce the E. coli by the same amount using just hot water. The novel RF pasteurization process is much faster than the existing commercial process and should lead to an increased percentage of eggs being pasteurized in the U.S., which in turn will reduce the number of foodborne illnesses.

Technical Abstract: The USDA-FSIS estimates that pasteurization of all shell eggs in the U.S. would reduce the annual number of illnesses by more than 110,000, yet less than 1% of shell eggs are commercially pasteurized. One of the main reasons for this is that the current process, hot water immersion, requires approximately 60 min to complete. In the present study, a radio frequency (RF) apparatus was constructed and a two-step process was developed that uses RF energy and hot water to pasteurize shell eggs in less than half the time. In order to select an appropriate RF generator, the impedance of the shell egg was measured in the frequency range of 10 – 70 MHz. The power density within the egg was modeled to prevent potential hotspots. Escherichia coli (ATCC 35218) was inoculated in the yolk to approximately 7.5 log CFU/ml. The combination process first heated the egg in 35.0 C water for 3.5 min using 60 MHz RF energy. This resulted in the yolk being preferentially heated to 61 C. Then, the egg was heated for an additional 20 min with 56.7 C water. This two-step process reduced the population of E. coli by more than 6.8 log. The total time for the process was 23.5 min. By contrast, processing for 60 min was required to reduce the E. coli by 6.6 log using just hot water. The novel RF pasteurization process presented in this study is considerably faster than the existing commercial process and should lead to an increased percentage of eggs being pasteurized as well as a reduction of foodborne illnesses.