Can Peanut Butter Go Bad? Here’s the Scoop.

Can peanut butter go bad? How do you know if it's no good? We'll tell you how to identify funky PB.

You reach into the pantry and find a jar of peanut butter that’s been sitting there for, well, who knows how long. After taking a peek at the best-by date (you’re in the clear!), you open the jar and stare into an ocean of oil. The peanut oil has separated from the solids during its long sit, which makes you wonder if it’s safe to eat.

Actually, it makes you question whether peanut butter is one of those foods you never knew had an expiration date!

Can peanut butter go bad?

Yes, it can go bad. But separated oil isn’t a sign of expired peanut butter. Natural peanut butter doesn’t contain additives, stabilizers or hydrogenated vegetable oils, all of which keep the peanut solids and oils together. The oil on top is actually a sign that you bought a high-quality peanut butter!

(Psst: There’s a genius tip to prevent this kind of separation, and it kind of changed my life.)

It’s hard for peanut butter to spoil because it’s mostly fat—that’s what makes it taste so good. Natural peanut butter only contains peanuts and sometimes salt, and while some nut butters also contain oil, sugar or stabilizers, there’s nothing there to add any water. This gives peanut butter its extremely low moisture content.

Since the majority of spoilage comes from microorganisms that grow in water, unopened peanut butter can happily sit on your shelf without going bad for a long, long time.

How do you know if peanut butter is bad?

You won’t find mold growing on it, but its high fat content means it can go rancid. (That’s the same reason we don’t recommend buying cooking oil in bulk.) Oxygen is the enemy here, and exposure to air can cause your peanut butter to develop off flavors. Rancid foods won’t kill you, but they also don’t taste great, either.

A sure sign of rancid peanut butter is a change in texture—perhaps it used to be soft and creamy, and now it’s dry and hard. It may also look darker in color or it might smell funky (sharp, bitter, soapy or metallic odors are a giveaway).

How should you store peanut butter?

To keep your peanut butter safe and fresh, it’s best to store it in the refrigerator. This is a requirement for natural or homemade peanut butter since these varieties lack preservatives. Once opened, it should last five to eight months past the best-by date.

If your peanut butter has been in the fridge for a while, it might be time to create an excuse to eat more peanut butter!

Have extra PB in the pantry? Find a recipe for dessert
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Lindsay D. Mattison
After years of working in professional kitchens, Lindsay traded her knives in for the pen. While she spends most of her time writing these days, she still exercises her culinary muscles on the regular, taking any opportunity to turn local, seasonal ingredients into beautiful meals for her family.