Quick Answer
Eggs that sink in water are not necessarily old. While fresh eggs tend to float and older eggs sink, there are other factors that can cause sinking, such as temperature and processing method. An egg can sink but still be perfectly safe to eat.
What Causes Eggs to Float or Sink?
The main factor that determines if an egg will float or sink is the size of its air cell. As an egg ages, air enters the egg and the air cell grows larger. The larger air cell gives the egg more buoyancy, making it float.
A fresh egg has a small air cell and is dense enough to sink. But as the egg ages and moisture and carbon dioxide escape, the air pocket enlarges and the egg becomes less dense. Once the air cell is large enough to keep the egg afloat, it will float in water.
Here are some other factors that affect floating:
Temperature
Eggs stored at colder temperatures will have smaller air cells and are more likely to sink. Eggs stored at warmer temperatures have expanded air cells and are more likely to float.
Processing method
Pasteurized eggs may sink more readily than non-pasteurized eggs due to the processing effects on the inner membrane. Pasteurization can weaken the vitelline membrane and allow interior liquid to move out, increasing the size of the air cell.
Freshness
Very fresh eggs can sometimes sink because the air cell has not had time to develop sufficiently. Over time, as air enters the egg, it will likely float.
Shell thickness
A thicker, coarser shell allows less air to penetrate so the air cell doesn’t enlarge as quickly. Eggs with thinner shells age faster and are more likely to float.
Does Floating or Sinking Indicate Egg Quality?
While floating can be a sign of an older egg, it does not necessarily mean poor quality. An older egg may still be perfectly safe to eat but with a few differences:
Floaters
Floating eggs tend to be older but can still be eaten. The white and yolk may be flatter and the yolk less round.
Sinkers
Sinking eggs can be very fresh with a round, perky yolk and thick white. They could also be older eggs that were temperature controlled to minimize air cell growth.
Off odors or appearance
Any eggs with an off smell or appearance should be discarded, regardless of floating or sinking. Floating does not definitively mean an egg is bad.
How Long Are Eggs Good For?
The length of time an egg can be kept before spoiling depends on storage conditions:
| Storage Method | Shelf Life |
|---|---|
| Refrigerator (40°F or below) | 3-5 weeks beyond pack date |
| Freezer (0°F or below) | Do not freeze eggs in shells |
| Room temperature | 2-4 weeks beyond pack date |
The pack date is the day the eggs were washed, graded and placed in the egg carton. The USDA recommends using eggs within 3 to 5 weeks of the pack date for best quality.
However, eggs that are 4-5 weeks beyond the pack date may still be used if they pass the float test.
What is the Float Test?
The float test is a simple way to check the freshness of eggs:
How to do the float test
1. Fill a bowl with cold water.
2. Gently place the egg in the water.
3. If it sinks, it’s fresh. If it floats, it’s older but may still be fine.
Floating eggs should be cracked open to check for any off odors before cooking. Any eggs that float and have an off smell or appearance should be thrown out.
Float test results
– If it sinks, it’s fresh
– If it floats vertically, it’s less fresh but likely ok
– If it floats horizontally, it’s older but may be safe if no odor
– If it floats and smells off, discard it
The float test works because of the size of the air cell inside the egg. Fresh eggs will sink, while old eggs float because of the enlarged air pocket inside the shell.
What Happens As Eggs Age?
Several changes occur as an egg ages and dries out:
Air cell growth
The air cell naturally grows larger over time as moisture escapes and air enters through the pores of the shell. The air pocket lift makes the egg more buoyant.
Thinning of the white
The egg white thins out as the egg ages and moisture is lost. This makes the thick albumen become more watery.
Yolk flattening
The yolk starts high and round in a fresh egg. As moisture is lost, the yolk absorbs water from the white, which makes the yolk flatten and become less round.
Loosening of the shell membranes
The inner and outer shell membranes separate and weaken as the egg ages. This makes it easier for bacteria and mold to penetrate the egg.
Enlargement of the yolk
As the white thins, the yolk absorbs more liquid. This causes the yolk to swell and flatten even more against the inside of the shell.
How To Store Eggs Properly
Proper storage prevents rapid moisture loss and keeps eggs fresh longer:
Refrigeration
Store eggs pointed end down at a constant 40°F or lower temperature. Eggs age faster at higher fridge temperatures.
Use within 3-5 weeks of pack date
For best quality, use eggs within 3 weeks of pack date or within 5 weeks if refrigerated consistently at 40°F or below.
Avoid temperature fluctuations
temperature changes cause condensation which can accelerate quality loss. Avoid leaving eggs out on counter overnight.
Store eggs alone
Keep eggs in their carton on an interior shelf, not side or fridge door. Eggs can absorb odors and flavors from nearby food.
Check expiration dates
Some state laws require sell-by or expiration dates on cartons. Check dates for freshness guidance beyond the pack date.
Clean dirty eggs
Washing eggs in water actually increases chances of spoilage. Instead, gently rub off dirt with fine sandpaper, emery board or brush.
How To Use Older Eggs
Instead of scrambling or frying, use floating eggs in dishes where appearance doesn’t matter:
Hard boil older eggs
The egg will be safe to eat hard boiled, even if the white and yolk are a little flat and watery. Use these for egg salads.
Use in batters and baking
Old eggs work fine in baked goods like cakes, cookies, muffins, pancakes or waffles. The leavening makes appearance unimportant.
Make pickled eggs
Floating eggs are perfect for pickled eggs. The acidity helps control bacteria growth.
Use in casseroles and quiches
When eggs are combined with other ingredients, minor aging defects won’t stand out.
How To Tell If Hard Boiled Eggs Are Bad
If a hard boiled egg has gone bad, you can tell by:
Sulfurous odor
A foul sulfur or rotten smell indicates bacterial growth. This can happen if boiled eggs sit at room temp too long.
Pink, blue, green discoloration
Unnatural colors like green or blue are a sign of mold. Pink or iridescent egg whites can mean spoilage bacteria are present.
Soft or slimy texture
Decaying hard boiled eggs will have a mushy or slimy texture versus firm, sliceable whites and yolks.
Dark yolk surface
As hard boiled eggs age, the yolk develops a darker ring around the outside that eventually turns grayish/green.
Dry, crumbly yolk
Very old hard boiled eggs have chalky, crumbly yolks versus a moist texture when sliced.
Can You Eat Moldy Hard Boiled Eggs?
Hard boiled eggs showing any signs of mold should be discarded. Mold penetrates porous foods and can make you sick even if you don’t see it. Boiled eggs should be eaten within a week.
What Is a Safe Room Temperature For Boiled Eggs?
Hard boiled eggs should be refrigerated and used within a week for best quality and safety. If served at room temp, boiled eggs should be discarded after sitting out for more than 2 hours above 40°F.
Can You Freeze Hard Boiled Eggs?
Freezing whole hard boiled eggs is not recommended. The rigid shell can crack and damage the contents during freezing. For storage, refrigerate hard boiled eggs and use within a week.
How Long Do Hard Boiled Eggs Last?
| Storage Method | Shelf Life |
|---|---|
| Refrigerator | Up to 1 week |
| Room temperature | Discard after 2 hours |
To maximize shelf life, store hard boiled eggs in the fridge and use within 7 days. At room temp, use within 2 hours. Discard any eggs with an off appearance or odor.
Conclusion
While floating eggs are older, they aren’t necessarily bad. An egg can sink but still be old if it was refrigerated properly. Check the pack date for optimal freshness and perform the float test if eggs are several weeks old. If eggs have an off smell or appearance, they should be discarded regardless of float results. With proper storage, most eggs are fine to eat for 3-5 weeks beyond the pack date. Hard boiled eggs should be refrigerated and eaten within a week for food safety.
