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

The fat in peanut butter is unsaturated, and so these cats are really good at sliding around. They don’t line up with each other as saturated fats can. So unsaturated fats are liquid at room temperature (usually). So, for regular peanut butter they’ll add another fat to help keep everything solid at room temperature.

The “peanuts and salt” peanut butter is liquid because it only has the unsaturated fat from the peanuts.

Edit: the oil and peanut matter separate out because the proteins and the oil don’t really like to stay mixed together. The oil would rather be with the oil, and the proteins would rather be with the proteins. They’re also different densities, which helps the separation.

Edit: fats are good at sliding around lmao