Mayonnaise (or mayo, if you prefer) is the most popular condiment worldwide. It’s a perfect pairing for fries, sandwiches, and salad, to say the least.

If you are a regular user, shelf life isn’t really an issue. But, if you’re just an occasional user, you probably end up with a jar that has been sitting in the fridge for months.

At some point, you need to confirm: Does mayonnaise go bad?

What about homemade mayonnaise? How long should you keep it in the refrigerator? How do you tell if mayonnaise is spoiled?

Fear not, we got your back. Keep reading to learn more about mayonnaise shelf life, storage conditions, and signs of mayonnaise going bad. Don’t worry, we will discuss both store-bought and homemade mayonnaise. So, read on!

Commercially-prepared mayonnaise is shelf-stable. Hence, storing a jar or a squeeze tube mayonnaise is straightforward and pretty much the same as other condiments, such as mustard.

That being said, unopened mayonnaise can safely sit in a cool, dry area, out of the heat and moisture. As usual, your pantry is always preferable. But, your kitchen cupboard or cabinet is an excellent place too.

When it comes to storage guidelines after opening, many people (maybe including you) are in doubt whether to refrigerate or not.

According to the USDA’s FSIS and Cornell University via FoodKeeper, storing mayonnaise outside the fridge after opening is considered safe. So, don’t worry if one day you forget to put it back in the refrigerator.

However, refrigeration is highly recommended to preserve the freshness and flavor for an extended period. That’s why every producer (such as Kraft and Hellmann’s) suggests keeping it refrigerated after opening, especially if you don’t use it frequently.

The story is entirely different from homemade mayonnaise, which is perishable and should be kept refrigerated at all times.

A classic homemade mayonnaise recipe always calls for egg yolk. As you’ve known probably, egg yolk is prone to Salmonella contamination⁠—a pathogenic bacteria causing food poisoning. Hence, homemade mayonnaise needs to stay chilled in the fridge and lasts for only 4 days maximum.

With commercial production, the egg yolks have to be sterilized to kill harmful bacteria. Next to that, store-bought mayonnaise is loaded with preservatives. Both treatments consequently extend shelf life and make mayonnaise shelf-stable.

Either way, always tightly close the lid when you’re not using it. There’s another thing worth pointing out: practice good hygiene.

Avoid double-dipping or using your finger to scoop out this dressing. Only use a clean spoon or utensils. These simple habits prevent microbial contamination and make a big difference to the shelf life of your condiments.

Let’s start by examining the container. If you have an unopened jar that looks damaged, such as swollen, leaking, dented, etc., don’t use it. Chances are mayonnaise is spoiled and no longer safe to use.

With proper storage, mayonnaise doesn’t quickly spoil. However, the flavor and taste slightly degrade over time. At some point, you may want to discard leftover mayonnaise because it’s not appealing anymore.

Telling mayonnaise going bad is not so difficult. You can always rely on your nose and eyes.

Common signs of mayonnaise going off include sour or putrid smell, presence of molds, yellowish, or darkened color. If you spot any of these signs, there’s no better option than to throw it out.

If your mayonnaise has separated liquid, this is a regular occurrence. It usually happens if you don’t use the sauce for a long while. As long as no other spoilage signs are spotted, it should be fine to consume. Give it a good stir to fix the consistency.

As mentioned earlier, store-bought mayonnaise is prepared with rigorous steps to guarantee its safety and shelf life.

Mayonnaise also relies on the addition of preservatives to make it last longer. Therefore, depending on the amount of preservatives, the shelf life of mayonnaise varies for every brand.

Don’t worry, you’ll see a “best by” or “best before” date on the package. Similar to other packaged foods, this date refers to quality rather than safety.

Under ideal storage conditions, you can expect unopened packages to last beyond this date, provided that the container is undamaged. Kraft suggests using mayonnaise within 30 days after the “best by” date.

Once opened, mayonnaise retains its freshness for at least 3 to 4 months if continuously refrigerated.

Homemade mayonnaise contains egg yolk, which makes it limited in shelf life. With proper refrigeration, homemade mayonnaise should be consumed within 2 to 4 days.

Once you prepare a salad or sandwich with mayonnaise, consume it immediately or keep it in the fridge for later.

The periods above are general estimates. There is no one-fits-all answer to how long mayonnaise lasts. The actual shelf life depends on the preparation method and storage condition.

As always, the best advice is to respect the expiry date. If you have expired mayonnaise, check for signs of spoilage before use. 

Unless otherwise stated, commercially-prepared mayonnaise is pasteurized. This process eliminates Salmonella and other harmful bacteria causing foodborne diseases. On the other hand, homemade mayonnaise should be avoided because the egg is unpasteurized. (*)

For further information, check the manufacturer’s website. It’s also advisable to consult your physician regarding permissible foods during your pregnancy.

Freezing mayonnaise is discouraged by most manufacturers. Although safety aspects are not likely affected, thawing results in separating liquid, and you’ll find it gross and unappealing.

Mayonnaise is made from at least oil, egg yolk, and acid (vinegar or lemon juice). So, mayonnaise is not a dairy product, since it doesn’t contain milk and its derivatives. Don’t forget to check the label for the ingredients list and allergen information if you have a dietary restriction.

Final Thoughts

Mayonnaise is a must-have condiment in many households. Similar to other sauces, mayonnaise also loses its flavor as time goes by and eventually goes bad.

Store-bought mayonnaise is shelf-stable. Unopened jars can safely sit in a dry, cool place. After opening, you can keep it both at room temperature or refrigerated. However, refrigeration is highly recommended to preserve the texture and flavor for longer storage.

Homemade mayonnaise should be kept refrigerated all the time. It is perishable and should be finished within a few days.

If you spot darkened color, molds, or sour smell and taste, mayonnaise is spoiled and no longer safe for consumption.

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*Photo by AndreySt/depositphotos