How to Tell If Eggs Are Good or Bad

egg float
egg float

Eggs are a healthy food choice. They are high in protein, low in saturated fat, and packed full of beneficial vitamins, minerals, and antioxidants. They belong in a well-stocked refrigerator. 

Sometimes though, life happens. We purchase healthy food items then forget to use them. Nothing can ruin your day faster than a rotten egg. 

In this article, we will discuss how to properly store eggs, how long they should last, and provide a few simple tricks to help you learn how to tell if an egg is good. 



5 Easy Ways to Tell If an Egg Is Still Good

You cannot know just by sight if an egg is still good. If you find older eggs in your fridge and suspect they are past their prime, here are a few simple tests you can do in your kitchen to help you decide if they are safe to eat or should be thrown away.

Check the Expiration Date

Many states require a sell-by date or expiration date printed on the side of egg packaging.

The expiration date represents the date when eggs are no longer considered fresh (1). It is meant for retailers to help manage their inventory and does not mean eggs need to be discarded after this date. 

Eggs that are graded by the USDA will be marked as grade AA or grade A on the front of the carton. Graded eggs are required to have a pack date printed on the carton (2). 

The pack date represents the date when the eggs were washed, graded, and packaged. However, it will not be a standard date in the format we are used to seeing on foods. 

Instead, there will be a three-digit code known as a Julian date printed on the carton. Julian dates go in chronological order so January 1 will be 001 and December 31 will be 365. For example, if you see 181 on the carton this means the eggs were packed on June 30th. 

Some egg cartons have a sell-by date instead of an expiration date. Per the USDA, the sell-by date cannot be more than 30 days after the Julian date (2).

If your eggs have expired do not just throw them away. They are still good to eat for two to three weeks after these dates have passed. You will need to use another trick to check if they are no longer fresh. 

Float Test

The float test is one of the most popular ways to test if eggs are old. 

Freshly laid eggs have no air inside. Over time, moisture evaporates from the egg whites and a small air cell begins to form. Eventually, enough air accumulates that older eggs will float in water.

To conduct the float test you simply drop a whole egg into a glass of water.

A fresh egg sinks quickly to the bottom of the glass. 

As an egg ages the air cell slowly expands. At first the egg will have a small enough air pocket that it will rest on the bottom of the glass but point upward. As the air sac expands eventually the egg floats to the top of the glass. 

Eggs are still perfectly safe to eat even if they fail the float test. 



Candling

Candling is the process of using light to determine the quality of an egg. In the old days this process was done with actual candles, now large egg producers use equipment that can detect cracked shells and defective eggs.

To do the candle test at home, bring your eggs into a dark room. You will need a bright source of light. A candle will work and so will a small flashlight (3).

Hold your egg close to the light source between your index finger and thumb. The light should illuminate the shell and allow you to “see” inside of the egg. 

Using the light source you should be able to see the air bubble which develops in the top end of the egg. The larger the air bubble, the older the egg, and the more likely it is to float in a glass of water. 

You should also see very little movement of the inside contents when you move the egg from side to side. This indicates freshness. The contents inside an older egg will move more freely inside the shell.

While the candling method will allow you to see the size of the air bubble inside an egg and give you some indication of overall freshness, like the float test it will not tell you if your egg has gone bad. 

You will just have to use the sniff test or look for unusual colors in the white or the yolk for signs that the egg has gone bad. 

Smell Test

The smell test is a simple way to help you learn how to tell if an egg is bad. 

A rotten egg has a very distinctive odor. That smell is caused by the presence of hydrogen sulfide, a gas created by the decay of nutrients inside the shell. 

If you suspect your eggs have gone bad simply crack one open. You will smell the distinctive rotten egg smell immediately. Even after cooking the sulfur smell will not go away. This is a sure sign that they are past their prime. 

Very old eggs will smell like sulfur without even being cracked open. Do not even bother trying to cook a bad egg, dispose of it, and purchase a dozen fresh eggs on your next trip to the store. 

Visual Inspection

You can learn a lot from visually inspecting an egg before you crack open the shell.

Begin by checking the outside of the eggshell for cracks or dents. Discard any broken eggshells. Bacteria can enter the egg and cause it to go bad. 

Also, check the shell for powdery spots as this can indicate the presence of mold. And if the shell has a slimy feel that can mean that there is bacteria growing on the eggshell. In both cases discard these eggs (4).

When you crack open your eggs there are other visual signs that to look for that can show you if they are no longer fresh or even if they have gone bad. 

As eggs age, the whites become thinner and the yolk becomes flatter. These are signs they are no longer fresh but are still safe to eat. 

Also, check for discoloration of the egg white or the egg yolk. If you notice blue-green, pink, or other off colors, your egg has gone bad. Discard it and wash the bowl carefully. 

Best Way to Store Eggs

Eggs are washed and sanitized soon after being laid to prevent contamination with salmonella, a bacteria often responsible for food poisoning. This process can damage the natural protective coating on eggshells called the cuticle (5). 

Sanitized eggs should be stored in the refrigerator. Cold temperatures prevent bacterial growth and keep any bacteria that may be present on the surface of the shell from moving inside the egg (6).

It is recommended that eggs be stored toward the back of the refrigerator where temperatures stay consistently cold. 

Eggs can also be frozen. It is not recommended to freeze them in the shell. Instead, crack eggs into a freezer-safe container then freeze the liquid. They will last for a year or more when frozen. 

How Long Do Eggs Last?

With proper storage, eggs will very slowly decline in quality over time. It is generally recommended to eat them within 3 to 5 weeks of purchase. 

If you forget when you purchased them and find eggs that are well past the date on the carton, use the methods above to determine if they are still fresh. Then use the smell test and a visual inspection to determine if they are bad. 

Try and keep eggs at room temperature for less than 2 hours. Bacteria that grow on the eggshell can quickly pass inside the egg and make us sick if they are not cooked to a proper temperature.

Health Risks of Eating a Bad Egg

Eggs are still safe to eat even if they are not fresh. Once they are past the expiration date be sure to inspect them and use the smell test to ensure they are still ok to eat.

The main reason people can get sick from eating a bad egg is a foodborne illness caused by salmonella or other bacteria. When eggs are cooked to the proper temperature harmful bacteria are killed. 

Egg whites will begin to solidify around 145 degrees, however, egg yolks are not fully cooked until they reach 160 degrees. You should never eat raw eggs unless they have first been pasteurized, a process of heat treatment that kills unwanted bacteria. 

Last Words

A little knowledge gained by using the above tips can save you a lot of time and trouble. At the store, look for eggs with the latest sell-by date, or look for a Julian date closest to the day you are shopping.

If you are not sure about the freshness of your eggs there is always the float test or candling. Remember that an egg is still perfectly safe to eat even if it is no longer fresh. 

Always do a quick visual inspection of your eggs both at the store and when you are ready to cook with them. Do not use eggs that are off-colored or you notice bad odors when they are cracked open. 

When in doubt, rely on your senses. Throw questionable eggs away if you are not sure and buy a fresh dozen.

Be sure to cook eggs to the proper temperature before eating them because you cannot see or smell harmful bacteria, even if they have passed all of the other tests. 

“What Do the Dates on Egg Cartons Mean?” Incredible Egg, www.incredibleegg.org/cooking-school/faqs/egg-carton-dates. Accessed 29 July 2020.

“Food Product Dating.” USDA, www.fsis.usda.gov/wps/portal/fsis/topics/food-safety-education/get-answers/food-safety-fact-sheets/food-labeling/food-product-dating/food-product-dating. Accessed 27 July 2020.

“Egg Nutrition & Fun Facts.” Incredible Egg, www.incredibleegg.org/egg-nutrition/egg-safety/#5. Accessed 27 July 2020.

“Egg Quality.” University of Florida, www.backyardchickenelearning.com/wp-content/uploads/2013/02/Egg-quality.pdf. Accessed 29 July 2020.

Samiullah. “Effects of Egg Shell Quality and Washing on Salmonella Infantis Penetration.” Int J Food Microbiol, 2013, doi:10.1016/j.ijfoodmicro.2013.05.002.

WHILEY, ALICE, et al. “Higher Storage Temperature Causes Greater Salmonella Enterica Serovar Typhimurium Internal Penetration of Artificially Contaminated, Commercially Available, Washed Free Range Eggs.” Journal of Food Protection, vol. 79, no. 7, 2016, pp. 1247–51. Crossref, doi:10.4315/0362-028x.jfp-16-078.


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