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Cool-Water Wash for Eggs Can Help Prevent Microbial Contamination

By Sharon Durham
December 19, 2006

Using cooler water to wash shell eggs during a second washing can help cool them quicker. This reduces the potential of foodborne pathogen growth both inside the eggs and on the eggshell surface, according to scientists with the Agricultural Research Service (ARS).

ARS food technologists Deana Jones and Michael Musgrove in the agency's Egg Safety and Quality Research Unit at Athens, Ga.—working with Auburn University colleagues A. Brooke Caudill and Patricia A. Curtis—looked at the frequency of Salmonella, Campylobacter, Listeria and other bacteria in eggs commercially washed in cool water. Their findings have been reported in the Journal of Food Safety.

ARS is the U.S. Department of Agriculture's chief scientific research agency.

Currently, processors who choose to produce eggs that qualify for the USDA quality shield are required to wash them in water that is at least 90°F, or 20 degrees warmer than the warmest egg entering the processing line. Furthermore, these eggs are required to be sprayed with a sanitizing rinse at least as warm as the wash-water temperature. To prevent the growth of potential foodborne pathogens associated with eggs, these warm eggs must then be cooled quickly for storage.

To ensure the eggs are safe for human consumption, USDA requires that all shell eggs be stored at 45°F or lower after processing. That's because Salmonella—the organism most often associated with foodborne disease and eggs—and other bacteria don't grow well at refrigerated temperatures. Getting to the target temperature quickly can make a big difference.

The researchers tested three water-temperature schemes in commercial dual-washer systems: water at 120°F for both washers; water at 120°F for the first wash and 75°F for the second; and both washers at 75°F. They found that using a warm temperature in the first washer, followed by a cool temperature in the second one, could provide the greatest benefit in terms of both reduced egg temperature and acceptable microbial levels.

While Salmonella, Campylobacter and Listeria were all detected in shell emulsion and wash-water samples from cool-water washing treatments, none were detected in the egg contents throughout the storage period of eight weeks.