Rapid cooling of eggs in the shell using liquid CO2 can double their shelf life, according to the most recent study from scientists at Purdue University.
Kevin Keener, PhD, a professor of food science at Purdue, has been investigating rapid cooling methods for eggs for a number of years. In their most recent study, Dr. Keener and his team used the rapid cooling method, which creates a sort of “cold snow” around the eggs, to bring them to 7 degrees Celsius (about 45 degrees Fahrenheit) within 25 minutes.
He then compared those eggs to traditionally cooled eggs. “Those are just cooled at ambient conditions, where the eggs are put into a carton at about 105 degrees Fahrenheit and they cool over time. It takes about 10-14 days for those eggs to cool to refrigeration temperature,” said Dr. Keener.
After 12 weeks of refrigerated storage at temperatures ranging between 5 and 7 degrees Celsius, only 37% of the control eggs were AA grade, the highest quality grade for eggs. Fifty-seven percent of them were grade A, and 6% were grade B. By contrast, 80% of the rapidly cooled eggs were still at AA grade, only 20% grade A, and none grade B. On average, the control eggs had declined to grade A after six weeks, while the rapidly cooled eggs maintained AA quality up to 12 weeks—“as if the chicken had just laid the eggs,” Dr. Keener said.
The CO2 process also appears to maintain the structural integrity of the egg’s membrane, which acts as a barrier to bacterial infection, for a longer period of time, Dr. Keener said.