Mayonnaise is a condiment with a complex reputation. On the one hand, this rich, tangy spread can elevate any sandwich or salad. On the other hand, every summer we are warned against the dangers of letting mayo-containing potato salad sit out too long or eating that tuna sandwich you accidentally left in the car.
When you buy mayo at the store, it is in the regular shelving, and often has a best-by date that is shockingly far in the future. But it says on the package to refrigerate after opening. And then there are those bottles you see at restaurants, blithely sitting out at room temp on tables and the sandwich station all day long. So, does mayo really need to be refrigerated or not?
The answer is a frustrating yes, and no.
The Complicated Case of Mayonnaise and Refrigeration
Before we dive in further, let's be clear that in this article we are only talking about commercial mayonnaise. Homemade mayo or aioli that are made with raw eggs will always need to be refrigerated and should be consumed within a few days of making it. But the jarred stuff? Less clear.
Mayonnaise, to be officially labeled such in the United States, as listed by the FDA, must contain 65% oil, with some percentage of egg yolk or egg product (including but not limited to liquid egg yolks, frozen egg yolks and dried egg yolks), lemon, vinegar and seasonings. While egg yolks are perishable at room temperature, the acidity in the vinegar and lemon juice helps to balance that risk, according to the USDA, and many commercial products are now touted as safe to keep at cool room temperature even after opening, much as you can with both ketchup and mustard.
Here is where the caveats come in.
In the case of all three of these condiments, but especially mayo, refrigeration will help to both prolong consumable life and maintain optimal quality of flavor. So while it is safe to keep those condiments in the pantry, you might find it worthwhile to stash them in your chill chest purely for flavor purposes.
Be sure to read the package directions very carefully before opting for pantry life for your opened mayonnaise. If you do choose to keep opened mayo in the pantry, buy only sizes of jars or bottles that you believe you will consume within a few weeks. Think about buying mayo in a squeeze bottle instead of a jar, since that will prevent contamination from knives and spoons going into the jar and help keep out oxygen and prevent the growth of mold. And if you see any mold or color changes, or smell any off odors, discard immediately.
Common Questions
How Long Can Mayo Be Unrefrigerated?
Commercial mayo that has a label that says it can be left unrefrigerated can typically be stored at cool room temperature (72°F or cooler), preferably in a dark place like a cabinet or pantry, for up to two months. Do not store it over or near any appliance that can create heat, especially a stove. If you do not have a squeeze bottle, be sure to only use clean utensils in the jar, and be cautious of cross-contamination.
What Happens When Mayo Is Not Refrigerated?
Mayo that is unrefrigerated will often have a looser texture and more pronounced flavor than mayo that is straight out of the fridge. The acid from the vinegar and/or lemon juice, plus any salt and sugar that are in the mayonnaise, will help to protect it from going off.
Why Do Restaurants Not Refrigerate Mayo?
Many restaurants use mayonnaise products that are specifically blended to be safe at room temperature for longer periods of time, or even to be shelf-stable after opening. They also tend to go through the product at a much more rapid rate than a home cook, so they may only be storing their opened mayo for a day or two.
Does Hellman's Mayonnaise Have to Be Refrigerated After Opening?
Most Hellman's products say to refrigerate after opening, with the exception of their squeeze bottles. If you love your Hellman's, but want to keep it out of the fridge, be sure to buy it in the squeeze bottle for safety.
What About Other Mayonnaise-like Products?
Products referred to as "salad dressings" like Miracle Whip, or other specialty versions like the Japanese Kewpie brand, all say to store in the fridge after opening. Always follow package directions when it comes to food storage.
The Bottom Line
While I think most of us will continue to store our mayonnaise in the fridge after opening, it is nice to know that the danger zone for some products is not as dangerous as previously touted. If you have ever had that sinking feeling when you walk into the kitchen in the morning to discover that the jar of mayo from the midnight sandwich raid was left out overnight, you may no longer have to automatically throw it away.
