In case you haven’t heard the news, egg prices are at an all-time high. Americans are scrambling to get their hands on a discount dozen—I, for one, have been paying specialty market prices at my local Stop & Shop. In times like these, we make sacrifices. Maybe you’ve stopped buying organic, settled for grade A instead of AA, or you’re buying your eggs in bulk. If you are stocking up on Costco-sized cartons, though, there’s something you should consider: How long do you have before those eggs go bad?
We worry about the expiration date of meat or fish, but what about other less obviously potent products? Can eggs go bad, just like those week-old chicken thighs giving your fridge an unsavory stink? The short answer: yes, eggs can go bad, but there are a few different ways for this to happen—some more dangerous than others.
How to tell if eggs are bad or good:
When we talk about an egg going bad, there are a few different things we might mean: 1) The egg can be compromised in quality—i.e. it won’t taste very good—but won’t pose a significant health threat. 2) The egg can be contaminated with salmonella, a pathogenic bacteria, which could lead to severe sickness if consumed. Let’s break down the ways an egg might be contaminated, and how to know if it’s okay to eat.
Over time, foods that have been sitting in your fridge can go bad without necessarily posing a health threat. “The classic example for this is spoiled milk,” explains Dr. Don Schaffner, Extension Specialist in Food Science, Distinguished Professor at Rutgers University, and co-host of the Food Safety Talk podcast. “Milk is not going to be unsafe if it has been pasteurized. But milk that’s been hanging out in the fridge for long enough will eventually not smell good, not taste good, and not look good. The same applies to eggs.”
So how can you tell if an egg has gone bad? You may have heard of a method called the float test or the water test, which involves placing an egg in a bowl of water and seeing if it sinks (meaning it’s good to use) or floats (no good). The theory is that, as an egg ages, the air pocket inside it grows larger, buoying an old egg to the surface. But, according to Dr. Schaffner, “there is no scientific basis for the egg float test.” So experimenting to see if your egg sinks or swims is not a reliable way to measure its quality.
The best way to tell if an egg is bad, he says, is to trust your senses. “If the egg looks or smells different than how eggs usually look or smell to you, that would be an indication that maybe some spoilage bacteria got in there,” advises Dr. Schaffner.
Maybe the egg is emitting a sulfurous smell or otherwise unpleasant odor—eggs can absorb smells from the inside of the fridge, so if you store it next to a fish fillet, the egg will eventually start to smell fishy. That egg’s not going to taste good and should be discarded.
Maybe you’re seeing visual cues, like a runny consistency in the egg whites, scientifically known as the albumen, or discoloration (bacterial contamination might cause the albumen to turn a greenish or iridescent color). Trash it! Note that if you see a blood spot on the egg yolk, that’s completely normal—it’s caused by a ruptured blood vessel. Cooked properly, the egg is safe to consume.
If you open up the carton to find that one of the eggshells has cracked, it’s best to discard that egg. Cracks in an eggshell—however small—open up an avenue for bacteria to get inside the egg, accelerating the process of spoilage. Here’s the golden rule: When in doubt, toss the maybe-rotten egg out. Make some oatmeal and get on with your day.
Note that there’s a difference between everyday bacterial spoilage and salmonella contamination. “It’s typically not the pathogens”—like salmonella—“that cause foods to look or smell gross,” says Dr. Schaffner. “It’s the spoilage organisms. They’re not going to make us sick, but they make the food unappetizing.”
Will eating an older egg give you food poisoning? Probably not, but it probably won’t taste very good, either. The real danger lies in the salmonella bacteria, which is not perceptible by taste, smell, or appearance.
Here’s the bad news: Salmonella is only detectable under a microscope, so the average person has no way to know if their egg is infected. “Just because the egg looks and smells okay doesn’t mean that salmonella is absent,” Dr. Schaffner warns.
The good news: Only about three out of every 10,000 eggs might contain salmonella in the albumen, so the chances of your carton being contaminated are quite low. Still, in case you do have one of those bad eggs, there are precautions you can take to curtail bacterial growth.
Salmonella lives in the albumen (or whites) of an egg, where a number of natural preservatives keep the bacteria in check. But as an egg ages, the yolk membrane—which separates the egg white from the yolk—starts to break down. Over time, salmonella bacteria may be able to breach into the yolk, where it’s able to run rampant. This means that as an egg ages, the risk of salmonella multiplying increases—but there are a few steps you can take to ward against this. The most important factor? Temperature.
“The lower the temperature, the slower the breakdown of that yolk membrane. Below a certain temperature, salmonella won’t be able to grow,” explains Dr. Schaffner. To discourage the spread of pathogenic bacteria, make sure your fridge is set to 40°F or lower.
Note that cooking an egg with salmonella to a temperature of at least 150°F will kill the bacteria. When handled properly, even a contaminated egg can be used in baking or other applications where the entire egg will be cooked through (i.e. no runny yolks).
How to preserve the shelf life of your eggs:
With proper storage, eggs should last for weeks in your fridge. But there are a few precautions you can take to keep your eggs fresher for longer. Here are a few shopping tips and other recommendations to prolong the life of your eggs.
Brands are not required to print use-by or expiration dates on their eggs, but if they do, they have to follow a few rules. If the carton lists an expiration or sell-by date, it “can be no more than 30 days from the day the eggs were packed into the carton,” according to the USDA, whereas use-by or best-before dates can be 45 days from the eggs’ pack date. Paying attention to these labels can help you determine which eggs in the aisle are freshest.
On some egg cartons, you might see what’s called a Julian date. The Julian date is a three-digit code that tells when the eggs were packed. The three digits indicate the exact day of the year when the eggs went into the carton (a number from 1 to 365). So if the eggs were packaged on January 2, the Julian date would read 002. If they were packaged on December 30, the Julian date would read 364.
“Consider what that date is, consider the rate at which you use eggs, and think about a plan to use them up by that date,” Dr. Schaffner advises. “But don’t obsess about it,” he adds. Fresh eggs can generally be stored for 3-5 weeks from the day they’re placed in the refrigerator. So if you stay in that window and remain mindful of the expiration date, your eggs should be fine to use.
The most important factor in egg safety (and food safety in general) is temperature. To keep eggs fresh, make sure your fridge is set to 40°F or lower; most modern fridges have a temperature sensor, but you can also take its temperature with a refrigerator thermometer. Also, be mindful of where in the fridge you store eggs. “A lot of older style fridges have a compartment for eggs on the door, and that’s probably not the best place to keep eggs because the door tends to be a little warmer than the rest of the fridge,” Dr. Schaffner says. The USDA advises storing eggs in the coldest part of your refrigerator.
Once you’ve put your carton of eggs in the fridge, that’s where they should stay. “A cold egg left out at room temperature can sweat, facilitating the movement of bacteria into the egg and increasing the growth of bacteria. Refrigerated eggs should not be left out more than 2 hours,” the USDA advises.
Freezing raw eggs for later use is also safe, provided they’re properly cooked once thawed. If you have a big batch of eggs that are close to expiring, crack them and whip them until homogenous. Stash the beaten eggs in an airtight container in the freezer for future scrambles or baking projects (1 large egg is equal to about 50 grams or ¼ cup beaten egg)—just be sure to thaw them in the refrigerator overnight, not at room temperature.
Now that you know how to tell if eggs are bad, it’s time to get cooking. Eggs on the verge? Make perfect, easy-peel hard-boiled eggs. Eggs gone to the dark side? Make tofu scramble instead.