Everyone sometimes buys a new carton of eggs ‘just to be on the safe side’, while there are still ten waiting in the refrigerator or on the counter at home. How do you recognize a bad egg? How can you limit the risk of this? And can you still eat an old egg with confidence or should you not? Professor Frank Devlieghere explains.
Why do some eggs go bad?
“There are three things that can make an egg no longer edible,” begins Professor Devlieghere. “Fungi can pass through the pores of the shell and cause a kind of thread formation that spoils the white of the egg,” says Frank Devlieghere, food microbiologist at Ghent University. “You will notice that when you break an egg: you will see those fungal threads. This type of decay occurs slowly, as the fungi have to travel a long way.”
A second form of spoilage is a bacteria that travels from the outside of the egg through the white to the yellow yolk and makes the egg bad. Once there, things happen quickly: the bacteria multiply, causing all kinds of rotting phenomena, such as the typical sulfur formation that is accompanied by black discoloration. This discoloration occurs because iron and sulfur come together there. By the way, it doesn’t always have to be black. The egg can also suddenly turn orange, green or red.” The third form is a little more annoying: salmonella. “Either it is there from the start, or it has to go all the way through the shell and then end up in the egg yolk.”
If an egg suffers from mold or if a bacterium penetrates from the outside of the egg to the yolk, you will really see, smell and taste it.
There is a clear difference between these three shapes and that difference matters when deciding whether the egg is still edible or not. “The first two have to grow to a higher level before you can really see, smell and taste it. Salmonella, on the other hand, makes you sick straight away. A few eggs – about three – per 10,000 are contaminated with salmonella. That doesn’t seem like much, but we do eat quite a lot of raw eggs, in mayonnaise for example or chocolate mousse and sabayon. Every preparation thereof therefore entails a risk. The only thing that helps: salmonella disappears when you fry the egg.”
How do you quickly recognize an egg that has gone bad?
“You see it less quickly than in the case of a bad apple. A trick to quickly notice it: put the egg in water,” says Devlieghere. “That helps you discover how old the egg is. A freshly laid egg will sink, because there is almost no air in such an egg. After a while, air does get into the egg, because the eggshell is not a 100 percent good protective layer. The shell contains small pores that allow bacteria and air to pass through. This happens slowly, but the air pocket then becomes larger. The egg first stands upright in water, after a while it floats. A tip: if you heat water to boil the egg, first put it in cold water. If it sinks, then it is fresh. If it floats, then it is old.”
Read more below the photo.
The water trick works according to professor Frank Devlieghere © Shutterstock / MuamerOsmanbegovic
Although that does not mean that the egg is automatically bad. “It just indicates it’s a four to six week old egg. An egg does have a long shelf life, because a bacterium must first travel all the way through the shell, membrane, egg white and egg yolk. That doesn’t happen instantly. You will usually find the expiration date on the carton of eggs, which is usually about 4 weeks after the laying date. With this trick you can easily see whether the egg is still edible after that date.”
A second trick to find out: break the egg. “If you see discoloration or mold lines, throw it away. Do you doubt the smell? Definitely don’t use it again. It is more difficult to estimate from the outside, if you break it, you can immediately see and smell whether it can still be eaten. The only thing you cannot see with the naked eye or smell is salmonella contamination.
You will not have condensation on the countertop, but the risk of salmonella is greater, because colder temperatures stop salmonella growing.
What is the best way to store eggs?
“There are two ways: at room temperature, on the kitchen counter or in the refrigerator. The big advantage of the refrigerator is that it is much more difficult for the bacteria to transfer to the yolk. Bacteria need energy to move and the cold takes away that energy. When it is cold in the refrigerator, the membrane remains firm for longer and is therefore more resistant to bacteria and air. A disadvantage of keeping it in the refrigerator is that as soon as you open the refrigerator, the egg comes into contact with cold air and warm air from outside. This causes condensation. That water can cause mold and bacteria. Storing eggs in their cardboard boxes helps against this, as the box provides extra insulation. You don’t have that condensation on the countertop, but then the chance of salmonella is greater: colder temperatures stop salmonella growing.”
What about home-grown eggs?
“In principle, they are the same as those from commercial, industrial production. The only disadvantage is that there is no quality control here as with industrial eggs. For example, there is a higher risk of salmonella, because it is not checked. Eggs from your own garden are usually a bit dirtier and have some feces on them. Be sure to rinse it thoroughly to avoid salmonella contamination.”
Also read:
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What is allowed in the microwave and what is not? Thanks to this simple trick you always know the answer
“The longer you walk around with high cholesterol, the greater the risk of heart problems”: dietitian shares 10 simple tips to eat away bad cholesterol (+)
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2024-01-21 06:30:00
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