The Short Answer
Eggs that float in water are usually not fresh and should not be eaten raw. However, floating eggs can still be eaten if cooked thoroughly. The float test is commonly used to check the freshness of eggs because old eggs fill with air, making them float. As an egg ages, air enters through the porous shell and the air cell inside gets larger, causing the egg to float. But this doesn’t necessarily mean the egg is rotten. As long as eggs are cooked well, they are safe to eat. However, raw or undercooked floating eggs pose a higher risk for salmonella contamination and foodborne illness.
Examining the Causes of Floating Eggs
There are a few reasons why an egg may float:
Age
The older an egg gets, the more air penetrates through the shell and into the egg. Eggshells are semipermeable, which means air can pass through tiny pores in the shell over time. As the egg ages, the air cell inside enlarges as moisture and carbon dioxide escape and oxygen enters. This causes the egg to become less dense than water and float. Freshly laid eggs will sink because they contain less air.
Temperature Changes
Temperature fluctuations can also cause air to enter the egg. Eggs experience expansion and contraction when moved between temperature extremes. This pressure change can force air through the shell. Refrigerating eggs after they’ve been sitting at room temperature may trap air inside and make them float. Storing eggs consistently at cooler temperatures helps limit temperature swings.
Cracks
Cracks in the shell allow air to seep inside rapidly, causing eggs to float. Cracks are often formed when eggs collide or experience pressure during transportation and handling. Always inspect eggs for cracks before purchasing or using.
Does Floating Mean the Egg is Bad?
A floating egg does not necessarily mean the egg has gone bad, but it is a sign of decreasing freshness. As eggs age, the quality declines:
At 7 to 10 days old
The air cell has grown larger but the egg still contains high-quality protein and nutrients. The whites may be more watery and the yolks less centered. Floating at this stage is due to air penetration but the eggs are still edible.
At 3 to 5 weeks old
The air cell has expanded to take up a large portion of the egg. The whites are thinner and the yolks flatter. The eggs may have a mild odor when cracked open. They are best used for cooking and baking at this point, not eaten raw or undercooked.
At 5 weeks and beyond
The air cell has grown very large, causing the egg to float completely. The whites are very thin and the yolks break easily. The eggs will have a distinct odor and flavor and should not be eaten raw. Hard boiling or cooking can control bacteria growth and make these eggs safer to eat if thoroughly cooked. Rotten eggs will have an unpleasant, sulfur-like smell and dark discoloration of the whites and yolks. These eggs should be discarded.
Are Floating Eggs Safe to Eat?
Floating eggs can still be eaten if handled and cooked properly:
Cook thoroughly
Thorough cooking is necessary to destroy harmful bacteria like salmonella that could be present in older eggs. Cook eggs until the whites and yolks are firm. Egg dishes like omelets, casseroles and sauces should be cooked to an internal temperature of 160°F to kill bacteria.
Use promptly
Use floating eggs as soon as possible after cracking them open rather than letting them sit out. Bacteria multiply rapidly at room temperature.
Avoid raw consumption
Older eggs should not be eaten raw or soft cooked. Consuming raw or undercooked egg whites or yolks increases the risk of salmonella food poisoning. Always cook older eggs thoroughly.
Check for normal appearance and smell
Inspect cracked eggs closely before cooking. Discard eggs with an abnormal appearance or odor, as those are signs of spoilage.
How to Test if Eggs Float
The float test is a simple technique for checking the age and quality of eggs:
Fill a bowl with cold water
Use enough fresh cold water to allow the egg to float freely. Cool water works best.
Carefully place the egg in the water
Gently lower the egg into the water and let go. Allow it to settle briefly.
Check if the egg sinks or floats
– A sinking egg is very fresh, only a day or two old.
– A floating egg is older, usually 3 weeks or more.
– Eggs that tip upwards or stand on end are moderately fresh, around 1-2 weeks old.
The angle of float can indicate the relative age of the egg.
Spin the eggs
Twirl the floating eggs to check for weak spots in the shell indicating cracks. Cracks make eggs more prone to contamination.
Break open and inspect before use
Carefully crack eggs and look for an enlarged air cell, thin whites, watery appearance, unusual odor or dark discoloration before cooking.
How Long Do Eggs Last?
With proper storage, eggs can stay fresh 4-5 weeks past the pack date or about 3 weeks after purchase. Here are some tips for maximizing freshness:
Purchase date-stamped cartons
Look for cartons with a sell-by or expiration date on them and choose the freshest eggs.
Keep eggs refrigerated
Store eggs in the coldest part of the refrigerator, not the door. Keep separator trays closed to prevent odor absorption.
Maintain consistent cold temperatures
Eggshells are porous so temperature fluctuations cause pressure changes that can draw bacteria and moisture in or out.
Use within 3 weeks
For peak quality and nutritional value, use eggs within 3 weeks of purchase. Older eggs are best for baking and cooking.
Check for freshness
Do the float test to identify older eggs. Check for normal odor, color, consistency and appearance when cracking them open before cooking.
Can You Freeze Eggs?
Eggs can be frozen raw or cooked, but they need to be prepared properly first:
Raw whole eggs
Do not freeze raw eggs in the shell. As eggs freeze, the contents expand which can crack the shell and allow bacteria to enter after thawing.
Raw egg whites
Place egg whites in a covered airtight container. Add 1/8 tsp salt per 1 cup egg whites to stabilize proteins. Stir gently to incorporate. Label with date and freeze. Use within one year.
Raw egg yolks
Do not freeze unmixed raw yolks. The high fat content causes them to thicken and gel.
Whole eggs
Beat eggs together with salt or sugar (1/2 tsp per 1 cup eggs) until blended and pour into airtight freezer containers. Label with date and freeze. Use within one year.
Cooked eggs
Cooked scrambled eggs, frittatas, and hard cooked eggs keep 6-8 months in the freezer. Wrap tightly in plastic wrap or foil and place in bags. Label with date. Thaw in the refrigerator before use.
| Egg Type | Preparation | Storage Life |
|---|---|---|
| Raw egg whites | Mix with salt or sugar, freeze in airtight container | Within 1 year |
| Raw whole eggs | Beat with salt or sugar, pour into freezer containers | Within 1 year |
| Cooked eggs | Wrap tightly in plastic wrap or foil, place in freezer bag | 6-8 months |
What Happens If You Eat a Bad Egg?
Eating spoiled raw eggs, especially runny yolks or whites, can cause foodborne illness. Symptoms may include:
– Nausea, vomiting, stomach cramps
– Diarrhea
– Fever
– Headache
– Muscle pains
– Chills
Food poisoning from bad eggs is commonly caused by salmonella bacteria. Salmonella can contaminate eggs through microscopic cracks in the shell, during the laying process, or via exposure in poultry farms or processing facilities.
Proper cooking kills salmonella and makes bad eggs safe to eat. But consuming raw, runny, or undercooked eggs increases the risk of bacterial contamination and sickness, especially in young children, pregnant women, elderly adults or those with weakened immune systems.
Most healthy people will recover from egg-related salmonella without treatment. See a doctor if vomiting and diarrhea last more than 2 days or if severe dehydration occurs. Antibiotics may be prescribed in severe cases.
To prevent foodborne illness, discard eggs that are cracked, leaking, or giving off a bad odor when opened. Cook eggs thoroughly until both yolks and whites are firm. Refrigerate promptly after cooking and eat within 3-4 days. Practicing good personal and cooking hygiene helps keep eggs safe to enjoy.
Conclusion
Floating eggs are usually a sign of age and decreasing freshness as air passes through the shell over time. But floating alone does not mean eggs are rotten or unsafe to eat. As long as older eggs are cooked thoroughly until the whites and yolks are firm, they can still be enjoyed without risk of salmonella poisoning. The float test is a handy technique for checking the freshness of eggs. While raw or soft cooked eggs should only be prepared with fresh eggs, older floating eggs are fine for use in baked goods, casseroles, sauces, and other dishes that require thorough cooking. With proper handling and refrigeration, eggs typically stay fresh 4-5 weeks past the pack date. Storing eggs properly, cooking them fully, and taking care not to consume raw, runny eggs will keep your egg dishes safe and delicious.