We Tested 9 Methods to Prevent Peanut Butter From Separating—Here’s What Worked

I have a love-hate relationship with peanut butter. I’m talking about the good stuff, the real stuff, the stuff made with peanuts, maybe a touch of salt, and none of the more processed add-ins like sugar, palm oil, and emulsifiers—the stuff that also, as a result of its minimal ingredients, is prone to separating. That’s where the hate comes in. I usually give a jar my best stir when opening it and then hope for the best, until I inevitably get close to the bottom and find unappealing bits of dry nut butter.

Clearly, my stir-and-hope-for-the-best method isn’t great, so I set out to find the best option for keeping nut butter combined until the very last spread. I tested nine commonly touted methods, and got a good arm workout in the process. In addition to my results, I also have some tips for how to revive any dry bits of peanut butter you may come across despite your best mixing efforts.

How We Tested

This testing requires starting with peanut butter that’s heavily separated, so I went to the store and grabbed nine oil-laden jars of the same brand of natural peanut butter—as in peanut butter that only contains peanuts and salt. In my case, Smucker’s Natural Creamy Peanut Butter had separated the most on my market’s shelves.

The following are the variables I tested; in each case I let the peanut butter sit untouched for two weeks after mixing before recording the results.

Mixing Methods: One big question is which methods work best for recombining the separated peanut butter. I tested several methods, including the good ole “jam a knife down into the jar and attempt to stir without sloshing peanut oil all over,” simply storing the unopened jar upside down to see if the peanut butter could mix itself as the oil flowed upwards, as well as several more time-consuming techniques that require transferring the contents of the jar to another container to then be mixed with a variety of implements (wooden spoon, whisk, immersion blender, food processor).
Storage Containers: After mixing, I tested storing the peanut butter in both the the original jar as well as wider vessels to see whether the shape of the vessel and the amount of surface area of exposed peanut butter on top had any effect on how quickly it re-separated.
Jar Position: In addition to flipping an unopened jar upside down in the mixing tests, I also checked how much an effect jar position had on separation after mixing. Was it more effective to flip a jar upside down after putting the recombined peanut butter back in it, or does it not matter at that point?

Storage Temperature: I kept recombined jars of peanut butter out at room temperature and also in the fridge to determine what effect temperature has on the rate of separation.

Results

Mixing Method

Method	What It Is	How It Worked
Flip Jar Upside Down	Turn the unopened jar of separated peanut butter upside down, the idea being that as the oil then flows upwards it will slowly mix itself into the thick peanut butter.	After two weeks, it ended up even more separated than when originally purchased.
Knife in Jar	Using a knife, attempt to recombine the peanut butter in the jar by plunging and stirring as best as possible without spilling.	Not the best, returning back to its original separation after two weeks but only separated slightly in the first two days.
Wooden Spoon	Transfer peanut butter to a larger container, then stir with a large spoon.	This didn’t seem to offer results that were much different than stirring with a knife in the jar itself, resulting in a thin layer of oil separation at the top.
Whisk	Transfer peanut butter to a larger container, then recombine with a whisk.	Did not work well: The peanut butter is too thick for the wires of a whisk. Only after an exhausting arm workout did I manage to blend the oil back into the dry peanut butter, and after two weeks it had separated again.
Immersion Blender	Transfer peanut butter to a container large enough to accept the blade end of an immersion blender, then recombine with an immersion blender.	Also did not work well, once again due to the thickness of the peanut butter. An immersion blender is not a good tool for this task.
Food Processor	Transfer peanut butter to a food processor, then process until re-blended.	This worked the best. After two weeks, the food-processor peanut butter mostly still hadn’t re-separated (when combined with some of the techniques discussed below, it didn’t separate at all). Downside is it means having to wash a food processor after doing this.

Jar Position

Some people claim that simply flipping a jar of brand new, unopened peanut butter over works as a method of mixing it back together, but as described above, my tests did not support that claim. There is an argument for flipping the jars over after mixing the PB together. The idea is that by inverting the jar, the “bottom” is always actually on top, so you avoid thick peanut butter settling on the actual bottom. This way, each time you turn it over to take some peanut butter out, you’re dipping into the thickest part while still able to access the thinner peanut butter below.

In my tests, this was a worthwhile practice for storing well-blended peanut butter, ensuring it remained in a more blended state.

Temperature

By chilling the peanut butter in the fridge, its oils congeal, which can slow the rate of separation. But while my tests confirmed this to be true, the difference between samples stored in the fridge versus room temperature were not so different to say it’s an absolutely required step. If you don’t mind working with cold peanut butter (and also if you make your way through a jar slowly and want to slow down rancidity), the fridge is a good idea. If you prefer PB that’s room temp, feel free to keep your jar in the pantry—it’ll still be fine after the initial remixing.

Containers

Since some of these tests necessitated transfering the peanut butter to a larger container, I took advantage of that to also test whether leaving the PB in that larger container afterwards was better than returning it to the jar. Following my testing, I’ve come to the conclusion that the container you leave the peanut butter in is less important to keeping it combined than the method you use to mix it.

On the one hand, if you’ve already removed the PB from its jar to mix it, it might be easier to leave it in a larger vessel after that instead of trying to pack it back into the jar. On the other, a wider, air-tight container will take up more room in your pantry or fridge than a regular jar of peanut butter would.

Conclusion: The Best Method of Mixing and Storing Peanut Butter

If your goal is utter optimization with no concern for the labor involved, then my results are clear: Blend the nut butter in a food processor, then store it in its original container upside down in the fridge.

But this may not be the best method for everyone. After all, dirtying the food processor is a pain, and transferring the nut butter back into its jar can be messy if you’re not careful. You could split the difference, using the food processor to blend the peanut butter and then transfer the result to a larger container for storage.

Otherwise, the option that requires the least amount of effort is stirring the peanut butter in the original jar with a knife, and then storing it upside down in the fridge. Just keep in mind it’s hard to blend it well, and you’ll need to give it another good stir from time to time, but that arguably is less of a pain than having to deal with a bunch of dirty dishes.

What to Do With Dry Bits of Nut Butter

If you’re reading this with one (or maybe more…it’s me, I’m guilty) jars with bits of dried up nut butter hanging out in your pantry, fear not! This tends to happen when the peanut butter gets dry because its oil separates out, leaving you with a thinner paste and therefore drier chunks of peanut butter. While you now know the best method for preventing that from happening from the start, you can still save those other jars. Our culinary editor Genevieve recommends adding in a few drops of neutral oil—essentially reincorporating what was extracted from the nut butter—to get it to stir, or tossing it in a blender if it’s a larger amount.