8 signs your carton of eggs has gone bad

There are some sure ways to tell if your eggs have gone bad. fishermansdaughter/Flickr
  • Roughly 75 billion eggs are produced in the US each year, according to the American Egg Board.
  • A carton of eggs, if properly stored, can last anywhere from 45 to 90 days, according to Kevin Murphy, food safety and sanitation expert and professor and chair of hospitality services at the University of Central Florida’s Rosen College of Hospitality Management.
  • Discoloration and a sulphur-like smell are a couple of ways to know if your eggs are no longer good, per Murphy.

The egg industry is a booming business. Each year, hens around the U.S. produce nearly 75 billion eggs, according to the American Egg Board. That’s about 10 per cent of the world’s entire egg supply, and consumers are responsible for buying up about 60% of those 75 billion eggs.

Eggs are a staple ingredient of many meals and recipes. Chances are you might have a carton of eggs in your fridge right now, but do you know how to tell if the eggs are still fresh or not? Kevin Murphy, food safety and sanitation expert and professor and chair of hospitality services at the University of Central Florida’s Rosen College of Hospitality Management, explains that sight, smell, and an egg float test are the three main things to consider when it comes to the freshness of your eggs. Here is how to know if your carton of eggs is bad.

The expiration date is long past

Egg carton
The date on your egg carton is referencing the egg’s freshness. Marco Verch/Flickr

This might seem like an obvious thing to do, but Murphy points out that the date printed on the packaging isn’t always an expiration date. A carton of eggs may not always need to be thrown out as soon as the date passes. The date is usually just an indicator of the egg’s freshness.

“The expiration dates are not expiration dates. Sometimes they are, but most of the time, the printed date is a best used-by date or sell-by date,” Murphy tells INSIDER. “So, that does not always mean that the eggs have gone bad. Food can be bad before the date. Eggs and other dairy products are temperature sensitive. If you left your carton of eggs out on the counter for an extended period of time, the eggs would actually go bad before the date.”

Per Murphy, “bad,” however, means that you shouldn’t eat the egg because it has the potential to make you sick. But, eggs can still be fresh even if they have passed their sell-by or used-by date.

“The fresher an egg is, like a lot of things, the better it tastes. In terms of freshness, a company can put a sell-by date or best used-by date on the carton. There is no regulation on that. The date is a good indicator of freshness,” said Murphy. “The closer you get to the date, the less fresh the eggs are going to be. But, just because you’ve hit that date or gone beyond it doesn’t mean that the eggs are necessarily bad.”

It fails the “float test”

The easiest way to tell whether or not a carton of eggs has gone bad is to do the float test. To conduct the float test, take one egg and place it in a bowl of room temperature water, according to Murphy. If the egg sinks to the bottom and lies flat on its side, it is still fresh. If the egg stands up on its end like it’s standing up, then the egg has gone bad.

“When an egg is first laid and it’s truly really fresh, it’s completely full there is very little air inside. But, egg shells are porous. So, as time goes by the inside starts to evaporate and is replaced by air,” said Murphy. “The amount of air in the egg depends on what happens to the egg when it is dropped into water. Generally, if an egg actually floats that’s the point when an egg has gone bad.”

It smells odd when sniffed

You might be familiar with the phrase “it smells like rotten eggs.” When an egg goes bag, it can emit a strong sulphur smell. The odor can be detected before you crack the egg open.

“Before you crack the egg, if you can smell sulphur through the shell, that’s a sign that the egg has gone bad,” said Murphy.

Its insides smell strongly of sulphur

Cracking an egg
If you notice a smell when you crack the egg, it’s best thrown out. Adam Berry/Getty Images

If you suspect your carton of eggs is going bad, but you can’t smell any sulphur, you may need to open the egg up and take a sniff.

“If you crack it open and smell sulphur, then the egg is definitely bad,” said Murphy. “A fresh egg shouldn’t have a bad odor to it.”

It’s discolored

When you go to cook with the egg, it should have a yellow center and cloudy egg whites. This means that the egg is fresh. If you crack the egg open and notice something different, your egg may no longer be good.

A fresh egg will have a yellow yolk. The exact shade of the yolk can vary depending on the type of feed the hens eats, according to the Egg Safety Center. A lighter-coloured yolk comes from hens that eat feed containing wheat and barley, whereas dark-coloured yolks are the result of a hen that eats foods like plants and corn.

“If you crack it and look at it and it’s got discoloration, like the egg whites are spotty or the yolk is spotty, then it’s gone bad,” said Murphy.

Sometimes specks of blood may appear after cracking open an egg. There’s nothing to worry about, though. The egg is still safe to eat, according to the Egg Safety Center. A small blood spot means that a small blood vessel may have ruptured in the yolk during ovulation or a “deposit of tissue during egg formation,” per the Egg Safety Center.

It has a flat, shapeless yolk

A fresh egg will have a bulbous and curved appearance. Over time, the yolk will flatten out and appear less round in shape. This can be another sign that your eggs are going bad.

“If you crack the egg and lay it out in a pan to cook it or on a dish, the yolk should appear round and bubbled,” said Murphy. “If it’s gone flat and is the same height as the rest of the egg whites, then it’s gone bad. The older the egg gets, the more it’s quality starts to deteriorate. It’s just not as obvious as a head of lettuce.”

It wasn’t stored at the correct temperature

Clerk restocking grocery
When refrigerated, eggs will last longer than if set out at room temperature. Flickr / Alex Barth

According to Murphy, a carton of eggs typically lasts 45 days. If the eggs are properly refrigerated, they could be good for up to 90 days.

“You’ve got to look at freshness from the time that the egg was laid, processed, manufactured,” he said. “It can’t be emphasised enough that temperature is really important to the difference between an egg going bad or not. Freshness is a matter of time – it’s a distance from when the egg was laid. The further you get away from the egg being laid and harvested, the less fresh it is.”

It fails the flashlight test

This technique is known as candling and dates back to the olden days, according to Murphy. The method can be used to determine if a carton of eggs is bad.

To do this, take the egg into a dark room. Hold a flashlight up to the egg to see how much air is in the egg. Remember, egg shells are porous. A fresh egg will not contain much air, but an egg that’s been sitting around for a while will contain noticeable amounts of air.

“You’ve got to get in a dark room and shine a flashlight through it and move it around to see how much air is in there,” said Murphy. “It’s a lot easier to fill up a bowl of room temperature water, but this is a fun science experiment. Way back when people used to hold a candle up to the egg to see check the amount of air in it.”

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