Does Mayonnaise Expire? Here is The Truth

Yes, mayonnaise does expire. But it lasts longer than milk or bread. What is in it matters a lot. Most store mayonnaise has vinegar or lemon juice. It often has preservatives too. These stop bacteria from growing fast.
An unopened store jar can last months past its "best by" date. Keep it in a cool pantry. It can stay good for three to six extra months. But after you open it, things change.
Opening the jar lets in air and germs. Even with preservatives, use opened store mayonnaise within two or three months. Keep it in the refrigerator. Homemade mayonnaise is different. It uses eggs, oil, and maybe lemon juice. It has no preservatives. So it expires faster. Use it within seven to ten days. Keep it in the fridge. Even if unopened.
mayonnaise does not spoil quickly. But it will not last forever. Waiting too long can make it go bad. That is not just unappetizing. It can make you ill.

Do homemade and factory mayonnaise last the same time?

No. How they are made is different. Factories use very clean mayonnaise filling machine. They often use pasteurized eggs. This reduces bacteria risk. Machines fill and seal the jars tightly. This keeps out air and dirt. Preservatives are added. So it is made to last. Unopened, it is good for months. Opened, it lasts months in the fridge.

Homemade mayonnaise is made in your kitchen. Even with clean tools, the seal is not as tight. You might use a regular jar. It is not as airtight. Without preservatives, bacteria grows once air gets in. So it is only good for about a week in the refrigerator.
Remember this: Do not treat homemade like store-bought. If you make it, use it quickly. Store-bought mayonnaise lasts longer because of machines and preservatives.

How can you tell if mayonnaise is bad? Look for some signs

check the texture：Good mayonnaise is smooth and thick. It looks even and creamy. If it is separated, that is a problem. Liquid on top and lumps below are bad. A little separation can happen. But if shaking does not fix it, it is likely spoiled.

smell it：mayonnaise should smell mild and tangy. It might smell like eggs or vinegar. If it smells sour or bitter, do not taste it. A sour smell means bacteria is growing. It is not safe.
look for mold：Mold can be white, green, or black spots. Look on the surface or jar edges. Even a tiny spot means throw it all away.
think about time：If store mayonnaise was opened over three months ago, throw it out. If homemade is over ten days old, throw it out. Do this even if it seems fine. It is better to be safe.

You can make mayonnaise last longer. Do some simple things

What is the shelf life of mayonnaise? The key lies in whether it is stored correctly. For unopened store mayonnaise, keep it in a cool, dark pantry. Do not put it near the stove or in sun. Heat spoils it faster. After opening, always refrigerate it. Cold slows bacteria. Do not leave it out over two hours.
Be careful when using it. Do not put a dirty utensil in the jar. Crumbs or other food can bring bacteria. Scoop what you need onto a plate first. Then put the jar back in the fridge.
If making homemade mayonnaise, make a small amount. Make only what you can eat in a week. Add a bit more lemon juice or vinegar. This acid helps it stay fresh longer. Keep it in a clean, airtight container.
For store mayonnaise, note the "best by" date. It is not an expiration date. But it is a good guide. If unsure when you opened it, write the date on the jar. That way you will not forget.

Does mayonnaise need to be refrigeration?

Unopened mayonnaise does not need the fridge. Store jars are sealed tight. Preservatives keep them good at room temperature. Keep an unopened jar in the pantry. Just keep it away from heat.
After you open the jar, you must refrigerate it. Breaking the seal lets in air and bacteria. At room temperature, especially when warm, bacteria grows fast in mayonnaise. So after opening, always put it in the refrigerator.
What about picnics or parties? If you take mayonnaise out, do not leave it out over two hours. If the day is hot, over 90°F, only leave it out one hour. After that, throw it away. It is safer than getting sick.
Homemade mayonnaise must always be in the fridge. Even if unopened. It has no preservatives. Cold is the only way to slow spoilage. Do not leave it out. Put it in the fridge right after making it.