If your jaw is on the floor, we can relate. But storing eggs upside down helps them last longer by preventing the air inside an egg’s shell from coming into contact with the yolks, explains egg farmer Lisa Steele, a fifth-generation chicken keeper from Maine and the author of the blog and the Fresh Eggs Daily Cookbook. This is important, because that air pocket may harbor potentially harmful forms of bacteria (such as salmonella) that can cause an egg to spoil faster. By turning the egg upside down, you’re introducing more separation between the yolk and the air pocket. “If there is bacteria inside the air pocket, that can obviously make an egg go bad—plus, the air is going to dry it all up,” says Steel.
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Understanding the anatomy of an egg helps explain why this trick works.
Knowing what’s inside an egg’s shell and how the components are arranged inside it makes it easy to see why it is best to store eggs upside down. You already know that inside every egg there is a yolk surrounded by egg whites. The egg whites also keep bacteria away from the nutrient-rich yolk. “The whites of an egg are alkaline versus acidic, so bacteria is not as readily able to form or grow inside the egg whites,” says Steele. “But if they get to the yolk where all the nutrients are, bacteria can certainly thrive and grow.”
What you may not realize, however, is that at the blunt end of the egg, there is an air sac. This air sac grows bigger and bigger as the egg gets older, Steele explains. This is because even though an egg shell may appear pretty solid, it actually has hundreds of thousands of tiny pores that allow air to seep inside. (This is how an unborn chick would be able to breathe inside the egg. It’s also the reason why a fresh egg will sink to the bottom of a glass of water, while an older egg will float.)
Air, of course, is lighter than the other contents of an egg. Therefore, if you store an egg with the blunt-side down, the air sac will be at the bottom, where it will push up against the egg whites and the yolk as it tries to rise to the top. As an egg gets older, the strands of proteins that tether the yolk to the egg whites begin to break down, making it easier for air to push the yolk around. If you keep eggs pointy-end down, however, you limit the effects of gravity, because the air sac is already on top.
“You always want the blunt end air sac to be at the top so the air stays where it belongs, and the yolk is safely down below encased in the egg white,” says Steele.
Benefits of proper egg storage
Because storing eggs upside down helps keep bacteria away from the yolk, the logic is that if you keep eggs upside down, you are less likely to get sick from eating them. This is especially important if you like your eggs runny rather than cooked all the way through, or if you are whipping up a batch of homemade mayonnaise or egg nog, both of which call for raw eggs. (Keep in mind that thoroughly cooking eggs is recommended by the FDA’s Food Safety and Inspection Service, because heat will kill most bacteria that are present.)
“You’re reducing your chance of getting salmonella probably or other foodborne illnesses, because that bacteria has not had as much chance to get to the yolk,” Steele says.
While Steele says the way you store eggs won’t necessarily affect their taste or nutritional value—eggs are not only a great source of protein, but also vitamins A, B12, D, and E—there is also an aesthetic reason for keeping eggs pointy side down. By limiting air movement inside the egg, you are also making sure that the yolk stays centered rather than being displaced by air. The position of the yolk won’t matter if you plan to scramble the eggs or bake with them, but if you’re looking to nail a perfect-looking boiled egg (who hasn’t been there?), it can make all the difference. “If you are hard-boiling eggs or making deviled eggs, they’re not gonna be all wonky,” says Steele. Talk about food for thought.
Here’s what a registered dietitian has to say about eggs, aka nature’s multivitamin:
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