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

Because the typical peanut butter you have that doesn’t have to be refrigerated has extra preservatives and hydrogenated oils in it that help inhibit bacteria growth.

That all natural peanut butter that is just ground peanuts and salt does not have that, so the oils in that peanut butter can go rancid.