Food Engineering

Technologies target Salmonella in eggs

March 29, 2003
As the U.S. government steps up efforts to reduce Salmonella Enteriditis illnesses resulting from eggs, food industry companies continue introducing treatments that either destroy the bacteria in the shell or significantly reduce its growth.

Using carbon dioxide, an egg-cooling unit reduces the temperature of freshly laid eggs by as much as 50 degrees in 80 seconds. Photo: Courtesy of Praxair


With Salmonella-infected eggs accounting for 300,000 illnesses a year, The President's Council on Food Safety last winter introduced an action plan that would eliminate any risk in eggs by 2010. Among other initiatives, the plan calls for identifying systems and activities necessary to ensure food safety from production to consumption. The plan also identifies promising developments in science and technology, including in-shell pasteurization.

Pasteurized Eggs, L.P. has begun rolling out eggs pasteurized by passing the product through a series of clean warm water baths that provide sufficient heat to kill the bacteria, but not cook the eggs. The eggs are quickly chilled in cold water to stop the cooking process, then inspected for cracks, treated with a sealant to prevent re-contamination, and packaged. Unlike irradiation, which can damage egg flavor and albumen integrity, the warm water method produces a product that "looks, cooks and tastes exactly the same as an unpasteurized egg," according to L. John Davidson of Pasteurized Eggs. First introduced at 1998's Poultry Show, the product is now available at East Coast supermarkets.

Meanwhile, manufacturer Praxair, Inc., recently informed the President's Council it has developed a means of rapidly cooling fresh eggs -- by as much as 50 degrees -- that could double the eggs' shelf life while reducing the risk of salmonella. Developed in conjunction with North Carolina State University, the method employs cryogenic carbon dioxide to bring egg temperature from as high as 109 F (the internal temperature of hens) to 40 to 45 F in about 80 seconds. Lowering the egg's internal temperature as quickly as possible reduces the possibility for increases in Salmonella populations, since cooler temperatures generally slow the bacteria's growth. In fact, current regulations indicate that eggs must be held at an ambient temperature of 45 F after processing and during transportation and retail storage.

Praxair has exclusive rights to market the technology, and the equipment has a patent pending.

The technology is currently being tested at Carolina Egg, a Nashville, N.C.-based company that processes about 1 million eggs per day. At the Nashville site, eggs in the test are laid, washed, sorted, graded, and then rapidly cooled in Praxair's tunnel cooler, cartoned, palletized and shipped. Normally, the eggs would need to cool in a refrigerator for days before being shipped. FE

Praxair Inc., 7000 High Grove Boulevard, Burr Ridge, IL 60521-7595 Tel: 630-320-4000