Scientists based at Purdue University have shown that cooling freshly laid eggs for a few seconds adds several weeks to the shelf life of eggs and helps to counter the harmful effects of the Salmonella bacteria.
Using a rapid-cooling process which involves liquid carbon dioxide, scientists were able to show that incidents of the harmful food poisoning bacterium Salmonella were greatly reduced and that the shelf-life of eggs could be greatly increased. According to a Purdue University press release, this was due to the super-fast cooling being able to to stabilize the proteins in egg whites. With the technique, newly laid eggs are placed in a cooling chamber and carbon dioxide gas at about minus 110 degrees Fahrenheit is generated.
The innovative method uses circulated carbon dioxide to create a thin layer of ice inside an egg's shell that cools the inside of an egg within minutes, strengthening proteins and increasing shelf life.
The science site Ivanhoe states that the reason that the eggs were protected from Salmonella was because the rapid cooling process protected the egg membrane. The membrane acts as a barrier that keeps harmful food spoiling bacteria from reaching the yolk. The yolk is a nutrient-rich reservoir for bacteria that bacteria can use as a food source.
Furthermore, there was no difference in the quality of the eggs prepared normally to eggs prepared using the new cooling method, when the eggs were examined at different periods of up to twelve weeks. This introduces economic benefits in relation to the shipment of eggs globally.
The research was led by Kevin Keener, a professor of food science at Purdue University. The findings were published in the journal Poultry Science. The reference for the paper is:
P. Banerjee and K. M. Keener. Maximizing carbon dioxide content of shell eggs by rapid cooling treatment and its effect on shell egg quality. Poultry Science, 2012; 91 (6): 1444