The Exploratorium is more than a museum. Explore our online resources for learning at home.

The Accidental Scientist: Science of Cooking
Candy Bread Eggs Pickles Meat Seasoning
Ask the Inquisitive Cooks    

"Is it okay to leave eggs un-refrigerated?"

Dear Anne and Sue,
Here in the U S we are told to be extra cautious when using and storing eggs. In my travels, I have found that other countries are not as cautious. In England, I bought eggs off the shelf un-refrigerated and kept them in a cupboard at home. In West Africa, though eggs were not refrigerated in shops, I kept them under refrigeration at home. I made mayonnaise from these eggs with no ill effects. Has the rest of the world not caught up with our caution? Is there a difference how eggs are handled worldwide?

Thanks. I enjoy your site.

Zenobia Oyenuga
Silver Spring, Maryland


Still have more questions? You'll find more answers in our archived monthly feature articles by the Inquisitive Cooks.

(Meet the Inquisitive Cooks)


Hello Zenobia,

There is indeed a great difference in how eggs are stored throughout the world. Let's take a look at the two major reasons for the caution exercised in the United States and Canada.

The biggest concern is safety. The other consideration is that an egg's quality changes as it ages.

Safety is an issue because protein-rich animal foods such as eggs are prone to carrying disease-causing microorganisms like the bacterium, Salmonella Enteritidis. The American Egg Board estimates one in 20,000 eggs in the United States, carries this bacterium inside the shell. While this figure is low, it is reason for caution, and for educating the public about the best way to store eggs.

Bacteria multiply most rapidly at warm room temperatures. If the bacterial load becomes sufficiently large,either on or inside the shell, it can cause illness. The chance of that happening is greatly reduced when eggs are stored at refrigerator temperatures.

Refrigerating eggs is not only a matter of safety, however. It's also the best way to keep eggs fresh. It's estimated that eggs age more in one day at room temperature than they do in one week in the refrigerator. And as eggs age, some of their cooking qualities are affected. The yolks and whites become thinner and more prone to breaking when you separate them. You'll also find these eggs harder to poach, as thin whites spread quickly throughout the poaching water instead of clustering around the yolk. And you may notice a large dent in the fat end of hard-cooked eggs. This happens as moisture and carbon dioxide evaporate from the white, allowing air to enter through the porous shell and enlarge the air space.

Granted, in parts of the world, people do eat unrefrigerated eggs without getting sick. Many variables account for this. In some countries for instance, people shop frequently—even daily—rather than storing food at home. So the eggs they buy are freshly laid and quickly consumed.

Where eggs spend prolonged periods at warm temperatures we suspect the instance of illness from Salmonella is higher than in locales where eggs are kept continuously refrigerated. Note too that the symptoms - diarrhea, abdominal pain, nausea and fever closely resemble "the flu". We seldom stop to consider that what we sometimes label as flu might really be a food borne illness. In communities where people are fortunate enough to know about food safety and have the opportunity to keep eggs cool, it makes good sense to do so.

Anne & Sue



- - - Science of Cooking - - - Webcasts - - - Ask The Inquisitive Cooks - - - Share & Discuss - - -


© Exploratorium | Use Policy | Privacy Policy