Should Peanut Butter Be Refrigerated?

We can pretty much all agree that peanut butter is a kitchen staple—but a lot of us have different opinions about the best place to store it. Some people prefer to keep it in the refrigerator, while others swear by pantry storage. So, the real question: Does peanut butter need to be refrigerated to stay fresh? Ultimately, the answer comes down to the type you have in your kitchen—natural or conventional.

How to Store Peanut Butter

There are two main types of peanut butter. One is made with stabilizers that keep the oil from separating (that's the regular, spreadable stuff), while the other is formulated from roasted peanuts (this is typically called natural peanut butter). The type you have will dictate your storage method.

Natural Peanut Butter

Natural peanut butter, which is made of ground roasted peanuts, should be refrigerated immediately after purchase. "Because it does not have preservatives or stabilizers, it is best refrigerated to keep it fresh and to prevent the oil from separating out," says Margarethe A. Cooper, PhD, assistant professor of practice and Victor P. Smith Endowed Chair in Food Safety Education at the University of Arizona. "The separated oil in unrefrigerated natural peanut butter is more likely to become rancid sooner, leading to unpleasant taste and texture."

Natural peanut butter is also more at risk for mold growth; refrigeration can help prevent this. 

Conventional Peanut Butter

Peanut butter with preservatives and stabilizers that keep it from separating don't need to be refrigerated. Instead, you can store conventional peanut butter in a cool, dry place, such as a kitchen pantry or cabinet. "Conventional peanut butter does not need to be refrigerated because it has added oils that stabilize it to keep the oil from separating out and to extend its shelf life," says Cooper.

Additionally, conventional peanut butter has low water activity, which means microbes generally can't grow in it.

How Long Peanut Butter Lasts

No matter where you store your peanut butter, both natural and conventional varieties have a shelf life.

Conventional Peanut Butter

Generally, an unopened jar of conventional peanut butter can last in your pantry for six to nine months, while an open jar can last for about two to three months. "To extend its shelf life past that time, it's okay to store in the fridge," says Lisa Young, PhD, RDN, an adjunct professor of nutrition at New York University. "It may last another three months or so."

Natural Peanut Butter

An unopened jar of natural peanut butter should be stored in the refrigerator immediately after purchase, where it can last for up to 12 months. "Once opened, refrigerated natural peanut butter is best consumed within three to four months of opening," says Cooper.

Signs Peanut Butter Has Gone Bad

There are some telltale signs a jar of peanut butter has spoiled, like if it smells or tastes bad. "When the oil gets rancid, it will give off an unpleasant smell," says Young. This is typically caused by the oil separating out, which may give the peanut butter a dry appearance. "Oil separation in natural peanut butter is more likely since it does not have stabilizers, and when the oil is exposed to oxygen this leads to oxidative rancidity, causing the characteristic unpleasant odor and flavor," says Cooper. Additionally, you should throw away peanut butter if you see any mold in the jar.