How to Identify Rotten Eggs

Have you ever been in the middle of preparing a meal or baking and realized that the eggs have expired? Or perhaps your eggs are in a carton with no expiration date, leaving you uncertain about when they should be discarded? Fortunately, recognizing spoiled eggs is very simple. This article will teach you how to distinguish between fresh and rotten eggs, along with some helpful tips to assess their freshness.

Place the eggs into a wide bowl or glass filled with cold water and observe how they float. Inside each egg is a small air pocket, and over time, air seeps through the eggshell, causing this pocket to grow. The more air that enters, the larger the pocket becomes, making the egg lighter and causing it to float.

• If the egg sinks to the bottom of the bowl, it is still very fresh.
• If the egg floats but still touches the bottom of the bowl, it has been stored for a while but is still good to eat.
• If the egg floats to the surface, it is no longer fresh. This doesn’t necessarily mean the egg is rotten or unsafe to eat, but it is recommended to crack it open and check the color (and smell) inside.

Hold the egg near your ear and shake it to listen for a sloshing sound. As an egg ages, moisture and carbon dioxide escape through the shell, causing the egg whites and yolk to shrink and dry out, and the air cell grows larger. A larger air cell creates more space inside the shell, leading to a sloshing noise when you shake it.

• A fresh egg will not make much noise, or perhaps no sound at all when shaken.
• If you hear a sound, it means the egg is older, but it doesn't necessarily mean it's spoiled and unsafe to use.

Crack the egg onto a plate or wide bowl to inspect the quality of the yolk and white. The egg's integrity decreases over time, so the yolk and white may not combine as they did when the egg was fresh. Observe if the egg spreads out on the plate or remains compact. If it spreads or looks runny with a thin white, the egg is no longer fresh.

• If the yolk breaks easily and flattens, it’s a sign the egg is old.
• If the yolk spreads easily across the plate, it means the chalazae (the thick strands connecting the yolk and egg white) have weakened, indicating the egg is past its prime.
• Check the egg white’s color. A cloudy white means the egg is very fresh, while a clear white indicates it is older (though still safe to eat).

Crack the egg and check its smell. This is the simplest way to identify a rotten egg. A rotten egg will have a strong, unpleasant odor when cracked. If you detect a sulfur smell right when breaking the egg (even before), discard it immediately.

• A rotten egg will smell bad, whether raw or cooked.

Crack the egg into a small dish and observe the color. The yolk’s color can vary depending on the hen’s diet, so a yellow or orange yolk does not indicate the egg's freshness. Instead, focus on the egg white. If it turns pink, green, or displays iridescent colors, the egg has become contaminated and should not be eaten. If you see dark or greenish spots inside, it means the egg has developed mold, and you should discard it.

• If the yolk of a cooked egg has a green ring around it, it means the egg was overcooked or cooked in high-iron water. It’s still safe to eat.
• If you find a blood spot or meat inside the egg, the egg is still safe and not rotten. These spots are caused by ruptured blood vessels during egg formation and do not affect its freshness.

Check the "sell by" date on the packaging. The sell-by date is marked as "do not sell after" or "EXP". This date typically occurs 30 days after the eggs are packed. Eggs that are kept refrigerated and are unbroken can still be safe to use for up to a month after the sell-by date.

• In the U.S., the sell-by date is printed in the month/day format. For example, eggs labeled 03/15 must be sold before March 15.
• The "sell by" date refers to the last day the eggs should be on store shelves. After this date, the eggs should be removed from display. However, this does not mean the eggs are spoiled or unusable after this date.

Check the "best before" date on the packaging. This date is usually printed as "use by", "use before", or "best before". It indicates the freshest period of the eggs, generally up to 45 days after packing. It's best to consume the eggs within two weeks after the best before date.

• The "best before" date indicates when the eggs are at their freshest, providing the best texture and flavor. It doesn't mean the eggs are spoiled or unsafe after this date.

Use the 3-digit code to check the packing date of the eggs. According to federal regulations (some states require it, others do not), it is not mandatory to display a sell-by or best-before date on the packaging, but most cartons show the packing date. This is typically represented as a 3-digit Julian code. For example, eggs packed on January 1 are labeled 001, those packed on October 15 are labeled 288, and eggs packed on December 31 are labeled 365.

• Look for the Julian date at the bottom of the carton. You'll find a printed code (a series of numbers starting with the letter P) that gives the packing date, followed by the Julian code.
• The European Union also requires packaging dates on egg cartons. Even if eggs are sold individually without cartons, this information should still be provided to consumers.

If you take eggs out of the fridge and leave them at room temperature for more than 2 hours, it’s best to discard them. Once eggs have been refrigerated, they should remain at a consistent temperature. If a cold egg is exposed to warmer air, it will sweat, creating conditions for bacteria to grow on the shell. Since the shell is porous, bacteria can enter the egg, causing contamination.

• To avoid temperature fluctuations, store eggs in the coldest section of the refrigerator, "not" in the door. The door's frequent opening and closing cause temperature changes, which may cause condensation on the eggs.
• If the eggs are unwashed and left at room temperature, you don’t need to refrigerate them. In many countries, including several European nations, eggs are stored at room temperature. This is safe because hens are vaccinated against Salmonella before laying eggs.

Follow the packaging instructions for egg storage based on your country. If you have hens that lay eggs and wonder when eggs spoil, you can rely on your country's packaging guidelines for egg freshness. Eggs can typically be used for at least two months, and sometimes even longer.

• If you're unsure about the egg's storage period or believe it's over two months old, look for signs of spoiled or old eggs to help you decide whether they are safe for cooking.

• If you're cooking eggs for elderly individuals or young children, it’s best to use the freshest eggs available. Although eggs can still be safe to eat for several weeks after their expiration date, you should exercise extra caution when preparing food for those with weakened immune systems, opting for the freshest eggs possible.