Eli5: why does “good” peanut butter need to be refrigerated?

Question

The only ingredients on the label are “peanuts, salt.”

We keep peanuts unrefrigerated in the pantry… we keep salt unrefrigerated in the pantry… so how come when you mash them together it makes something that (according to the jar) must be refrigerated after opening?

P.S. I put “good” in quotes because all peanut butter is good. What I mean by “good” peanut butter is the healthier stuff that you have to mix the oil back into and there are only the above mentioned ingredients.

In: 2133

Answer 1

Nut oils also tend to go rancid if you leave it out for too long. I like to store my peanut butter in the fridge after I open it to keep it fresh longer.