Breakthrough: New way to pasteurize raw eggs
March 31, 2014
• Kills Salmonella, doesn't harm egg quality
• A bit of radio waves, a dash of water – voila!
(ARS photo by Peggy Greb)
Classic Caesar salad, old-fashioned eggnog, some homemade ice cream — and many other popular foods — can be made with raw eggs. But from home kitchen cooks to fancy restaurant chefs, raw egg ingredients have been shunned because of fears of sickening the diner with Salmonella.
Now, there’s a breakthrough from scientists with the U.S. Department of Agriculture.
The Agricultural Research Service says its experiments have produced a faster way to pasteurize raw, in-shell eggs without ruining their taste, texture, color or other important qualities.
The pasteurization procedure targets Salmonella because an estimated one out of every 20,000 chicken eggs produced in the United States has a high risk of being contaminated with it, notably Salmonella enteritidis, a pathogen has been associated with eating raw or undercooked eggs, and can cause diarrhea, stomach cramps, fever, and—in some instances — death.
USDA chemical engineer David Geveke and his colleagues have shown that their pasteurization process, currently in the prototype stage, killed 99.999 percent of the Salmonella that they injected into raw in-shell eggs for their laboratory tests.
When commercialized, the pasteurization procedure could provide an alternative to an hour-long hot-water-immersion process, a technique that is used commercially in the United States to pasteurize fresh shell eggs.
The procedure that Mr. Geveke's team developed begins with positioning each raw egg between two electrodes that send radio waves back and forth through it. While that is happening, the egg is slowly rotated, and is sprayed with water, to offset some of the heat created by the radio waves.
Unlike conventional heating, the radio-frequency (RF) heating warms the egg from the inside out. That's critical to the success of the process. It enables the dense, heat-tolerant yolk at the center of the egg to receive more heat than the delicate, heat-sensitive egg white.
A comparatively brief hot-water bath comes next. The warmth of the bath helps the yolk retain heat to complete the pasteurization. The bath also pasteurizes the egg white without overprocessing it.
From start to finish, the treatment takes approximately 20 minutes, making it about three times faster than the hot-water-immersion technique.
The idea of using RF heating to kill pathogens in foods isn't new. But using RF heating to kill pathogens in eggs apparently is novel. Mr. Geveke and his colleagues are evidently the first to pair RF heating with a hot-water bath to pasteurize raw, in-shell eggs.
Mr. Geveke works at the USDA Agricultural Research Service Eastern Regional Research Center in Wyndmoor, Pa. He collaborated on the research with ARS chemical engineering technician Andrew B.W. Bigley, Jr. at Wyndmoor, and with Christopher D. Brunkhorst of the Princeton Plasma Physics Laboratory in Plainsboro, N.J.