Expire is such a strong word. This peanut butter is dead, it’s no longer among the living and like many dead things, you probably don’t want to eat it. Well, maybe peanut butter isn’t the best example. It’ll be a long time before you inherit all those peanuts.
Peanut butter in a plastic jar at the supermarket usually has a sell-by date of about 18 months after it hits the shelf. Past this date, if it’s unopened it’s still perfectly good. Opened, peanut butter will slowly develop off-flavors of rancid nuts over the next five or so years before it’ll taste so bad not even the most peanut butter-obsessed child will go near it. But it’s still very unlikely to make you sick. (Unless of course you have a peanut allergy.)
Fresh peanut butter doesn’t have the preservatives and emulsifiers of the shelf-stable stuff. Within two weeks, the oil will separate, float to the top, require mixing back in and go rancid more quickly. You’ll want to toss fresh peanut butter after two months.
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