If you have a jar of peanut butter that has been left out for a few months, it's when you start to wonder, "How long does it last?" or "does it still taste good?". Can you say your peanut butter is gone bad if the date on its label has passed? Do you want to know if it is still safe to eat? If any of these has happened to you, keep reading to figure them out. Even if you leave peanut butter out at room temperature, it will last for months, but not forever. Ground peanut fat will go bad if it's kept for too long or in a warm place. When that happens, you should throw it away. How To Tell If Your Peanut Butter Has Gone Bad? Instead of being soft and peanut-like, PB that has gone bad will taste sharp, bitter, and "off." It might also start to smell funny, like nail polish remover, though this isn't always easy to notice. If you buy peanut butter with added sugar, like Skippy, you might not notice that flavor changes as much because the sugar changes the overall taste. The process of rancidification takes months. That means that if you use your PB often, you won't notice any changes. 
You can only see them if you look at an old jar after a few weeks or months. Now, it's not dangerous to eat rancid nuts, so if you eat a tablespoon of rancid PB, you shouldn't feel bad right away. Besides having that unpleasant taste, that is. Is Separated Peanut Butter Spoiled? Peanut butter that has separated, or has a layer of oil on top, is fine and safe to eat. You just need to stir that oil back in, and you're good to go. There are a few ways to make separated peanut butter nice and easy to spread: Use a spoon or a fork to stir it. If the ground peanuts on the bottom aren't too dry yet, that works great. With a knife, cut through the dry peanut mass all the way to the bottom and make a couple of lines. So, some of the oil will sink to the bottom and mix with the ground peanuts. After a few hours, it should be easier to stir. Keep the jar on its side. Since peanut oil rises to the top, this is how it will try to get to the bottom. Again, you'll probably need at least a few hours and maybe even a few days to get good results. And don't forget to close that lid well. Use a blender or food processor. You can try to mix the oil and dry mass together with a strong blender or food processor. Don't forget to turn off the tool right away if the blade won't move. 
Spreads made with peanut butter and another oil usually don't separate and stay nice and spreadable even after being stored for a while. That's why PB doesn't separate, even though it doesn't have any extra ingredients, and popular brands like Skippy don't. Lastly, if the whole bottom is very dry and you can't mix it all together, it's fine to throw that PB away because it's not good. Now that we know that let's talk about the real signs that peanut butter is going bad. How to Tell if Peanut Butter Has Gone Bad? If any of the following are true: It smells bad. If your peanut butter tastes funny, sharp, or bitter, it's time to throw it out. The same thing is true if it smells sour or likes chemicals. It's completely separated, and stirring won't help. Again, this is normal for plain peanut butter and can be fixed. But if you can't fix the nut butter, you have to throw it away. Since peanut butter is mostly fat, it doesn't tend to grow mold. But if the jar is opened and gets dirty, you might find mold in it. If so, throw away the spread. 
Going bad takes time. Your peanut butter might not be bad yet, but you might notice that the taste has changed, and you no longer like it. How Long Can You Keep Peanut Butter? Peanut butter can usually be kept for 9 to 12 months. And that time will be a couple of months longer if it has preservatives. Once you open a new jar of peanut butter, it usually stays good for about 6 months or until a couple of weeks after the date on the jar. Putting it in the fridge will add a few months to that.
- Unopened Jar
On the label of a jar of peanut butter, there is a "best-by" date that is less than a year from when the spread was made and put in the jar. That date is not the peanut butter's expiration date, but rather a rough estimate of how long it should last. Most of the time, if you store the nut butter well, it will last at least a couple of weeks, and maybe even months, after that date. And even longer if you refrigerate it. As long as the jar isn't opened, rancidity happens pretty slowly because there isn't any fresh air to speed it up. So, if you have two jars of PB with the same date and they are both stored in the same place, the one you open today will be fresher than the one you opened a few months ago. 
Still, peanut butter won't last forever if it's never opened. It will still go bad, and if you open a jar a few months after the date on it, you might find that it's already gone bad.
- After Opening
Peanut butter is good for about 6 months after it has been opened, or a couple of weeks after the date on the jar, whichever comes first. If you open a jar of peanut butter a week before the "best by" date, it will probably still be good for a month or two, but it probably won't last the whole six months. When you open your peanut butter jar for the first time, fresh air gets into it. This speeds up the process of the spread going bad. Because of this, some sellers say how long their peanut butter stays good after it has been opened. For example, Peanut Butter & Co. says that you should finish the jar within six months. Some, like Skippy, just want you to pay attention to the date on the label and not worry too much about when you opened it. What is certain is that the taste will get worse the longer the jar is open. But how quickly peanut butter goes bad depends on things like what's in it and how it's stored. It also varies from brand to brand. 
How to Keep Peanut Butter Fresh Peanut butter should be kept in a cool, dark place away from sources of heat. The kitchen cupboard and the pantry are both good places. Even after you've opened the jar, you don't have to put it in the fridge to keep it fresh. Peanut butter can last for a long time without going bad, and most sellers say to keep it at room temperature before and after opening. So, it stays nice and easy to spread. But you don't have to keep peanut butter in the fridge, and doing so makes it last longer and keeps its quality. So, if you only use it once in a blue moon and want it to last as long as possible, you might want to keep it in the fridge. Another good thing about refrigeration is that it slows down the separation that happens naturally, which I talked about in the section on how food goes bad. But it has a drawback: nut butter is harder to spread when it's cold. And you might have to let it sit out on the counter for a few hours to get it soft enough to spread again. Last but not least, don't forget the basics of storing peanut butter, like keeping the lid on the jar when you're not using it and using clean knives, spoons, or whatever you use to get some PB. 
Should Peanut Butter Be Kept In The Fridge? You don't have to put peanut butter in the fridge, but it helps if you want to keep it for a long time or if the oil keeps separating. The biggest problem with putting peanut butter in the refrigerator is that it gets harder and harder to spread. In other words, you can put peanut butter in the fridge, but there are pros and cons to doing so. And you have to figure out the math. I know that some sites say you should put PB in the fridge after you open it, but most sellers don't say that. And if you're not dealing with one of those problems, I don't think it's worth losing that readability. Overall, if you need to keep peanut butter for a long time, you should put it in the fridge. If you don't want to do that, keep it at room temperature and drink it often.