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Effects of Extended Storage on Eggs

By Sharon Durham
June 2, 2004

Egg quality and usefulness are safely maintained beyond the sell-by date if the eggs are stored properly, according to Agricultural Research Service scientists in Athens, Ga.

ARS food technologists Mike Musgrove and Deana Jones with the agency's Poultry Processing and Meat Quality Research Unit tested the quality and functionality of table eggs during a 10-week storage time, long beyond the current 30-day industry standard for storing eggs on the store shelf. Properly refrigerated and handled, eggs are considered safe for consumption for four to five weeks beyond the sell-by date.

Musgrove looked at bacteria like Salmonella, Escherichia, Enterobacter, Klebsiella and Yersinia that can contaminate eggshells and--if handled or processed improperly--remain on eggs when they reach the consumer. However, Musgrove found that after washing and packaging, eggs showed no bacteria of the Enterobacteriaceae family until the fifth week after processing. Washing eggs according to current guidelines removes bacteria from their surface, reducing the chances of microbes getting into the eggs once they are cracked in preparation for consumption.

An egg's shell and membranes under the shell provide a barrier that limits the ability of organisms to enter. A natural protective coating, called the cuticle, helps to preserve freshness and prevent microbial contamination of the egg. This coating is damaged or removed by processing, but a thin layer of oil may be applied during processing to help preserve internal quality. The eggs are then placed in cold storage and shipped.

Jones studied the functionality of the eggs during 10 weeks of storage. Eggs are found in a wide range of foods, including baked goods and mayonnaise. Over time, eggs can lose their ability to fluff up an angel food cake or make creamy mayonnaise, but according to Jones, they didn't show a marked decrease in quality during the 10-week test period.

Read more about the research in the June issue of Agricultural Research magazine.

ARS is the U.S. Department of Agriculture's chief scientific research agency.