Carbon dioxide cooling may reduce Salmonella risk

Rapidly cooling eggs with carbon dioxide could decrease the risk posed by Salmonella, according to recent research.

A cooling process developed through research at Purdue University appears to not only inhibit bacterial growth but also alter the pH in the eggs sufficiently to increase the activity of lysozyme, an enzyme that lyses gram-positive bacteria, a university announcement states. The gas is drawn into the egg shell during cooling, reversing the pH rise that occurs as carbon dioxide escapes from freshly laid eggs.

The announcement indicates increasing such lysozyme activity would increase safety of the eggs.

Kevin M. Keener, PhD, a professor of food science and one of the study authors, said previous evaluations of use of the carbon dioxide cooling process have indicated the treatment would cost 3 to 7 cents for every dozen eggs, with the largest portion of that cost coming from delivery of the gas. A commercial version of the cooling system could bring egg temperatures to 45 degrees in less than two minutes, preventing population explosions among the small numbers of Salmonella organisms deposited near or on the yolk membranes in about 1 in 10,000 eggs, he said.

Dr. Keener said additional research indicated egg quality was substantially improved among eggs treated with the rapid cooling method, and a report on those findings was under review.

The article "Influence of carbon dioxide on the activity of chicken egg white lysozyme" was published the journal Poultry Science (Poult Sci 2011;90:889-895). More information is available at ps.fass.org.