Quick Answer
Generally, eggs that float are not safe to eat raw or undercooked. An egg floats when air gets trapped inside the shell and makes it more buoyant. This air pocket forms when eggs get old and the contents start to evaporate through the porous shell. Old eggs are more likely to contain harmful bacteria like Salmonella. However, a floating egg may still be fine to eat if it’s cooked thoroughly. The float test is not 100% foolproof but it’s a helpful way to check an egg’s freshness.
What Makes An Egg Float?
As an egg ages, moisture and carbon dioxide escape through the shell, leaving more air space inside. This makes the egg more buoyant, so it’s able to float in water.
A floating egg isn’t necessarily rotten or bad, but it is past its prime freshness. Over time, the quality deteriorates. The whites get thinner and the yolk flattens. Bacteria have had more time to multiply to potentially dangerous levels in the nutrient-rich interior.
Why Do Old Eggs Float?
There are a few reasons why old eggs float:
- Moisture loss – As an egg ages, water evaporates through the porous shell. This contributes to the air pocket inside.
- Carbon dioxide loss – Carbon dioxide escapes through the shell over time, leaving more air space.
- Yolk thinning – The yolk absorbs water from the white which thins out the whites.
- Air cell growth – The air cell or air pocket naturally grows larger as an egg ages.
All these changes make the egg more buoyant in water.
What Are Signs Of An Old Egg?
Some visual and physical signs that indicate an older egg:
- Thin, watery egg white
- Flattened yolk that breaks easily
- Enlarged air cell
- Pale, dull yolk color
- Weak, thin, or cracked shell
- Floating in water
As the egg contents deteriorate, unpleasant odors may develop like sulfur or rotten smells. The shell may look normal but the inside can still be compromised. Testing for freshness is important.
Are Floating Eggs Safe To Eat?
Floating eggs can still be eaten if cooked thoroughly. However, raw or lightly cooked floating eggs are generally unsafe.
Safe If Cooked Completely
Thorough cooking can destroy any harmful bacteria present in an aging egg. Whole floating eggs hard boiled for at least 15 minutes are considered safe to eat. Using floating eggs in fully cooked dishes like casseroles or baked goods is fine too.
Proper cooking brings the internal temperature high enough to kill pathogens. The whites and yolks must be firm throughout with no visible liquid.
Unsafe Raw or Undercooked
Consuming raw or soft boiled eggs that float is risky. Lightly cooked whites or yolks can still harbor dangerous bacteria.
Food poisoning is a major concern with undercooked floating eggs. Salmonella rates tend to be higher in old, floating eggs. Other bacteria like E. coli and Listeria are also possible risks.
At-risk groups like pregnant women, children, and those with weakened immune systems have greater vulnerability to foodborne illnesses. So floating eggs present an even higher hazard for them.
What Is A Float Test?
A float or water test is a simple way to check the freshness of eggs.
How To Do A Float Test
To perform a float test:
- Fill a deep bowl with cold water.
- Gently place the egg in the water and see if it sinks or floats. An egg that tilts upwards or stands on its pointed end still counts as floating.
- A sinking egg is fresh while a floating egg is old.
The float test works because:
- A fresh egg will sink because it has a dense interior.
- An old egg will float because of the enlarged air cell inside.
Tap water is fine for the float test. Using cold water prevents expansion of the air cell.
Interpreting Float Test Results
- Sinks – Egg is fresh and ok to eat raw or slightly cooked
- Floats – Egg is old and should be hard boiled or cooked before eating
- Stands upright – Egg is aging and should be used soon
The float test has some minor limitations. Very fresh eggs can sometimes float briefly. Floating could also just mean the egg was chilled in cold water. But it’s generally a reliable freshness indicator.
How Long Do Eggs Last?
With proper storage, eggs typically stay fresh 4-5 weeks beyond the pack date or about 3 weeks after purchase. But this can vary based on handling. Here are some general timelines for egg freshness:
Uncracked, Unwashed Eggs
- Pack date to 3 weeks – Very fresh
- 4-5 weeks – Use quickly
- Over 5 weeks – Older but ok if cooked thoroughly
Washed Eggs
Since the protective cuticle may be washed away, these eggs have a slightly shorter shelf life around 3-4 weeks from pack date.
Refrigerated Eggs
Keeping eggs refrigerated in their carton helps prolong freshness to 4-5 weeks past the pack date.
Room Temperature Eggs
At room temperature, eggs may last only 2-3 weeks before quality declines. Keep eggs refrigerated.
Preserving Freshness
To help keep eggs fresh longer:
- Store in refrigerator at 40°F or below
- Keep eggs in their carton – prevents moisture loss
- Check expiration or pack dates
- Use older eggs first
Aging decreases egg quality but old eggs can still be used if cooked thoroughly.
What Makes Floating Eggs Unsafe?
The main safety risk with floating raw eggs is increased bacteria levels. Here’s why bacteria multiply over time:
Salmonella
Salmonella rates are significantly higher in older, floating eggs. This dangerous food poisoning bacterium can contaminate eggs through fecal contamination.
Over time, any Salmonella present can multiply to unsafe levels inside a floating egg. Eating lightly cooked floating egg with live Salmonella bacteria can lead to salmonellosis.
Other Bacteria
Other bacteria like E. coli, Staphylococcus aureus, and Listeria are also found more often in aged eggs. Given time to multiply, these bacteria may also reach hazardous levels, especially if eggs are temperature abused.
Undercooked floating eggs could contain dangerous amounts of these bacteria and cause severe gastrointestinal illness.
Ideal Bacteria Growth Environment
The nutrient-rich interior of eggs is an ideal environment for bacteria to thrive and multiply over time. Pathogens like Salmonella grow best between 40°F-140°F. So sitting at room temperature accelerates bacteria proliferation in an aging egg.
Given warm conditions and nutrients, bacteria counts can increase to risky levels in an old, floating egg. Proper cooking is critical to destroy any potential bacteria.
How To Check For Fresh Eggs
Besides the float test, there are a few other ways to identify fresh eggs:
Check the Pack Date
The pack date on the carton indicates maximum freshness. Eggs are best within 3-5 weeks of this date.
Sell by dates are not expiration dates – eggs should be fine for a while after. But the freshest eggs will be before the sell by date.
Candle Eggs
Candling involves shining a bright light through the egg. A high yolk, small air cell, and thick white indicate freshness.
Open and Inspect
Carefully cracking eggs open reveals signs like firm whites, rounded yolks, and minimal odor.
As eggs age, the whites thin out, yolks flatten, and unpleasant sulfur smells may develop.
Compare Eggs in Water
Placing eggs in water side by side shows relative freshness. Fresher eggs sink lower in the water.
Floating eggs are old while those sinking below the bottom are the freshest.
How To Use Old Floating Eggs
To recap, floating eggs can still be eaten if cooked thoroughly:
Hard Boiled
Fully cooked hard boiled eggs are safe. Boil for at least 15 minutes after the water reaches a boil.
Casseroles & Bakes
Baking floating eggs into casseroles, breads, and other dishes is fine since the high cooking temperature kills bacteria.
Well-Cooked Omelets & Frittatas
Using floating eggs in omelets and other egg dishes is ok if eggs are cooked until completely set. No visible liquid should remain.
Avoid Raw Consumption
Do not eat floating eggs raw or soft boiled. Consuming undercooked whites or yolks puts you at risk for Salmonella and other food poisoning.
With proper cooking, older floating eggs can still be safely enjoyed in many dishes.
Why Do Some Fresh Eggs Float?
In rare cases, fresh eggs can briefly float too. Here are a few reasons why:
Cooling After Washing
Eggs contract slightly as they cool after washing. This can cause a small air pocket allowing fresh eggs to float temporarily.
Farm Temperature Differences
Eggs produced in a very warm environment may temporarily float at cooler grocery store temperatures. Let them sit 1-2 days as eggs acclimate before retesting.
Very Cold Water
Chilled water straight from the refrigerator may cause fresh eggs to float briefly. Allow water to reach room temperature before float testing.
While floating can mean an egg is old, sometimes very fresh eggs float too. Consider it a warning sign to test egg quality further.
Do All Bad Eggs Float?
No, floating is not a foolproof indicator of overall egg quality and safety. Here are exceptions when bad eggs may sink:
Freshly Laid Eggs Sink
Very rarely, a contaminated egg could sink right after being laid before air cells expand. Salmonella can infect ovaries and get inside eggs before the shell forms.
Hairline Cracked Eggs
Eggs with hairline cracks too small to release gases outward may sink even when old. Bacteria could have entered through the cracked shell.
farm-raised eggs in the United States?
Here are some key facts about farm-raised eggs in the U.S.:
- Over 90 billion eggs are produced annually, making eggs the #1 protein consumed in the country.
- Iowa is the #1 egg producing state, accounting for over 16% of national output.
- The top 5 egg-producing states are Iowa, Ohio, Indiana, Pennsylvania, and California.
- Almost all farms that produce eggs are considered family-owned.
- There are about 200 egg-producing companies in the country with flocks of 75,000 hens or more.
- 98% of all eggs produced come from large regulated farms with cage-free or enriched colony housing.
- Only about 2% of production comes from specialty niche farms like pasture-raised or free-range.
- Total number of egg-laying hens is around 325 million, predominantly White Leghorn breed.
- Average number of eggs laid per hen annually is just over 300.
- Top egg production systems:
- Cage-free barns – 67%
- Enriched colonies – 31%
- Cage systems – 2%
- Per capita egg consumption is approximately 278 eggs per person per year.
In summary, the U.S. egg industry produces around 90 billion eggs annually from hundreds of large companies and family farms across the country. Most hens are housed in cage-free or enriched colony systems.
Conclusion
Floating eggs are generally old and can contain higher levels of harmful bacteria like Salmonella. It’s unsafe to consume them raw or lightly cooked. However, thoroughly cooking floating eggs makes them safe to eat.
While the float test is a helpful freshness indicator, it’s not 100% foolproof. Some spoiled eggs may sink, and very fresh eggs may float temporarily. But in most cases, floating signals lower interior quality and higher risks.
To enjoy eggs safely, its best to inspect shells, check pack dates, refrigerate promptly, and use floating eggs only in fully cooked dishes. With proper handling and cooking, eggs can remain a nutritious protein source.
