Passed down from generation to generation, the habit of placing the egg in a glass of water is a common gesture in many kitchens, as a way of checking if the food is still good. Popular wisdom says that if the egg sinks, it can be consumed, but if it floats, it should be thrown away. Science confirms part of this idea, although the test does not fit everything.
Paula Teixeira, professor and researcher in the area of food safety at the Higher School of Biotechnology of the Catholic University in Porto, assured the Viral portal that “an egg that floats should not be consumed”.
The expert explains that, as the egg ages, an air pocket forms inside, which causes it to rise to the surface. This behavior indicates that it is no longer fresh and that the risk of contamination increases.
If the egg floats, the risk increases
According to the researcher, “the older the egg, if it is contaminated, the greater the likelihood that contamination levels will increase over time”. It also highlights that an egg that floats may have lost quality and safety, even if it does not show visible signs of deterioration.
However, if the opposite happens, that is, if the egg sinks, it does not necessarily mean that it is free of pathogenic microorganisms. The so-called “egg test” can help assess freshness, but it is not a reliable diagnostic method to ensure food safety. “The egg can sink and still be contaminated”, explains the same source.
Test shows freshness, not security
Professor Paula Teixeira recalls laboratory experiments carried out at the Catholic University, in which eggs contaminated with high levels of salmonella continued to sink in the water. “The egg still went to the bottom, because it was still a relatively fresh egg”, he describes.
This means that the float test only serves as an indicator of shelf life. If the egg rises to the surface, it is a sign of aging and should be discarded; if it sinks, it may be fresh, but there is no guarantee that it is free from contamination.
Care to take before and after purchase
In addition to checking the egg’s reaction in the water, there are other essential measures to ensure safety. According to the same source, it is important to ensure that the shell is clean and intact at the time of purchase. “When the egg is already broken or cracked, the likelihood of contaminants from the outside passing through to the inside is also greater,” he says.
The expert also advises keeping eggs in the refrigerator, both to prevent the growth of microorganisms and to preserve quality. “An egg that is left outside the refrigerator will have a much more liquid white and a yolk that will fall apart”, he adds.
Consumption must be quick and prudent
Another recommendation from the portal is not to store eggs until the expiration date. “They should be consumed as fresh as possible,” explains the website. Homemade eggs should only be used in recipes that use high temperatures, in order to eliminate any pathogens.
In short, the glass of water test can indicate whether the egg has aged, but it is not a substitute for good food safety practices. If the egg floats, it is best not to eat it.
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