About 74 billion eggs are produced in the United States each year, out of which less than three percent are pasteurized. The purpose of egg pasteurization is to reduce the risk of infection from bacteria like Salmonella. The current pasteurization process involves immersing the eggs in hot water at temperatures between 54 and 60 degrees Celsius.
While the process effectively mitigates risk of Salmonella infection, the process causes proteins in the heat sensitive egg whites to denature and coagulate. This occurs because the heat has to go through the egg white before reaching the egg yolk, which is more heat-tolerant and also where Salmonella likes to grow. Not only does the current pasteurization process take about an hour to complete, but it adds about an extra $1.50 to the price of a dozen eggs.
Simply put, the conventional pasteurization process gets the job done, but is susceptible to improvement.
Insert Agricultural Research Service (ARS) researcher David Geveke, who (along with some colleagues), developed a technology to rapidly pasteurize eggs while sharply reducing the number of annual illnesses caused by egg-borne Salmonella. Geveke, a chemical engineer at the ARS Food Safety and Intervention Technologies Research Unit in Wyndmoor, Pennsylvania, utilizes radio frequency (RF) waves to heat eggs without damaging the egg whites while effectively killing salmonella.
Geveke and his colleagues connected electrodes to eggs and immersed them in warm water, where they were heated with RF waves for 3-5 minutes, and rotated every minute or so to prevent the formation of hot spots. The eggs were then placed in a hot bath to give the yolks additional time to finish pasteurizing.
The procedure’s results were published in the Journal of Food Engineering in 2016, and showed the treatment reduced pathogen levels by 99.9999 percent, which equates to pasteurizing eggs in hot water. The entire process took 23 minutes, making it almost three times faster than conventional pasteurization methods. The expedited time of the new process also prevented any form of degradation on the eggs.
The patented RF process ensures the yolk gets heated more than the albumen, and should lower pasteurization costs, along with the price of pasteurized eggs. RF technology is already used to reduce pathogens in foods like almonds, spices, and wheat flour.
Most Salmonella cases involve eating undercooked or raw eggs used in dishes like Caesar salad, eggnog, along with Béarnaise and hollandaise sauces. Salmonellosis, the name of the actual bacterial infection, causes symptoms like diarrhea, stomach cramps, fever, and can sometimes be fatal. Infants, preschoolers, pregnant women, and the elderly are more vulnerable to Salmonella infections, since pasteurized eggs are commonly used by nursing homes and other institutional kitchens.