Jun 28, 2011 


US research shows cooling eggs may decrease food-borne disease



Purdue University's research by Dr Kevin Keener has indicated that cooling eggs after they are laid may enhance the natural defences they have against bacteria such as Salmonella.


Once eggs are laid, their natural resistance to pathogens begins to wear down but a Purdue University scientist believes he knows how to rearm those defences.
Keener, an associate professor of food science at Purdue University, created a process for rapidly cooling eggs that is designed to inhibit the growth of bacteria such as salmonella. The same cooling process would saturate the inside of an egg with carbon dioxide and alter pH levels, which he has found are connected to the activity of an enzyme called lysozyme, which defends egg whites from bacteria.
"This enzyme activity is directly related to the carbon dioxide and pH levels," said Keener, whose results were published in the journal Poultry Science. "An increase in lysozyme would lead to increased safety in eggs."
Freshly laid eggs are saturated with carbon dioxide and have pH levels of about seven. Over time, the pH level rises to nine and carbon dioxide escapes, Keener said. As that happens, lysozyme becomes less active.
Keener saturated purified egg white lysozymes with carbon dioxide and tested different pH levels. He found that at both high and low pH levels, the addition of carbon dioxide would increase lysozyme activity by as much as 50%.
The cooling process would create the same conditions, he said.

The additional lysozyme activity would give eggs more time to self-eliminate harmful bacteria.

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