Once laid, eggs' natural resistance to pathogens begins to wear down, but cooling them can rearm those defenses, said Kevin Keener, a professor of food science at Purdue University.
In his process, the quick cooling is designed to inhibit the growth of bacteria such as salmonella, a Purdue release said Tuesday.
The cooling process can saturate the inside of an egg with carbon dioxide and alter pH levels, which Keener said are connected to the activity of an enzyme called lysozyme that defends egg whites from bacteria.
"This enzyme activity is directly related to the carbon dioxide and pH levels," he says. "An increase in lysozyme would lead to increased safety in eggs."
"When we cool the eggs, carbon dioxide is sucked inside the shell," Keener said. "We're able to re-saturate the white of the egg with carbon dioxide, returning it to that original condition when the chicken laid it."
Food and Drug Administration studies suggest if eggs were cooled and stored at 45 degrees or less within 12 hours of laying, there would be an estimated 100,000 fewer salmonella illnesses from eggs in the United States each year, Keener said.