# Shelf life of peanut butter..............
**URL:** https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427
**Category:** Factual Questions
**Created:** [August 25, 2010, 6:20pm UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427 "2010-08-25T18:20:15Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@Captain\_Midnight](https://boards.straightdope.com/u/Captain_Midnight)
#### Post date: [August 25, 2010, 6:20pm UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/1 "2010-08-25T18:20:15Z")
Reading the post about the shelf life of honey…
What is the shelf life of peanut butter? I have never seen rotten or spoiled peanut butter. This seems like a product that if kept sealed in a container (like what they are now), that the product would last forever.
Anyone know? Is Skippy out there? Jiff?
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### Author:  [@beowulff](https://boards.straightdope.com/u/beowulff)
#### Post date: [August 25, 2010, 6:29pm UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/2 "2010-08-25T18:29:57Z")
I may never “rot” or get moldy, but it does get rancid. I’ve never tried to see how long it stays edible, but it’s probably around a year, maybe less.
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### Author:  [@mcgato](https://boards.straightdope.com/u/mcgato)
#### Post date: [August 25, 2010, 6:31pm UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/3 "2010-08-25T18:31:59Z")
I work for Skippy (among other products). The main reason peanut butter goes bad is that the oil in it oxidizes. In a sealed jar, the amount of oxidation should be minimal, so it should last a long time in a sealed jar. I think that the current plastic jars do allow some oxygen to get in over time, so it won’t last forever. I think the current shelf life on the label is 14 or 18 months, which is what testing indicates is about when the aged peanut butter is noticeably different from fresh peanut butter. There’s a recent thread about butter going bad, and most of that discussion also applies to peanut butter.
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### Author:  [@Smeghead](https://boards.straightdope.com/u/Smeghead)
#### Post date: [August 25, 2010, 7:14pm UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/4 "2010-08-25T19:14:13Z")
Yep. Same deal as honey and butter. Not enough water for microbial spoilage, so all you have to worry about is oxidative rancidity.
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### Author:  [@dracoi](https://boards.straightdope.com/u/dracoi)
#### Post date: [August 25, 2010, 7:48pm UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/5 "2010-08-25T19:48:53Z")
A jar of peanut butter was only partly used during a camping trip and got left in my camping gear for two years. We decided to try it and could not tell any difference in flavor. It was kept in the plastic jar, tightly sealed, in the dark and in a cool place in the garage.
So maybe not forever, but clearly longer than 2 years if stored well.
Natural peanut butter is supposed to have a shorter shelf-life than the more processed commercial varieties, but I wouldn’t be surprised to see it last 2 years too. You’d just have to do some serious work to mix the oil back in.
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### Author:  [@Si\_Amigo](https://boards.straightdope.com/u/Si_Amigo)
#### Post date: [August 25, 2010, 7:55pm UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/6 "2010-08-25T19:55:21Z")
I just had a confortation with my GF over whether or not to put the PB in the fridge because I kinda freaked out on her when she did just that. Thank god that Jiffy actually puts on thier packaging that no refrigiration is required after opening or we would have had an ongoing battle consisting of the movement of the PB from in and out of the fridge over a long period of time until I just gave up and stopped eating PB.
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### Author:  [@Smeghead](https://boards.straightdope.com/u/Smeghead)
#### Post date: [August 25, 2010, 8:21pm UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/7 "2010-08-25T20:21:11Z")
> [@dracoi](#):
>
> Natural peanut butter is supposed to have a shorter shelf-life than the more processed commercial varieties, but I wouldn’t be surprised to see it last 2 years too. You’d just have to do some serious work to mix the oil back in.
“Natural” peanut butter, meaning the kind with liquidy oils that separate out, are liquidy because they have more unsaturated fats. There are more double bonds in the chains of hydrocarbons, which cause kinks in the molecular structure, making it more difficult for them to pack together…never mind. The point is that these oils have more targets for oxidation, meaning that they’re more likely to go rancid quicker.
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### Author:  [@dracoi](https://boards.straightdope.com/u/dracoi)
#### Post date: [August 25, 2010, 10:05pm UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/8 "2010-08-25T22:05:05Z")
> [@Si\_Amigo](#):
>
> I just had a confortation with my GF over whether or not to put the PB in the fridge because I kinda freaked out on her when she did just that. Thank god that Jiffy actually puts on thier packaging that no refrigiration is required after opening or we would have had an ongoing battle consisting of the movement of the PB from in and out of the fridge over a long period of time until I just gave up and stopped eating PB.
How are you guys doing on the mustard and ketchup? 🙂
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### Author:  [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)
#### Post date: [August 25, 2010, 10:17pm UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/9 "2010-08-25T22:17:12Z")
Peanut butter also contains a fair amount of salt, which should help to preserve it.
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### Author:  [@mcgato](https://boards.straightdope.com/u/mcgato)
#### Post date: [August 25, 2010, 11:21pm UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/10 "2010-08-25T23:21:35Z")
I should also mention that with natural peanut butter, the oil separation puts the oil closest to the air in the head space at the top of the jar making oil oxidation easier.
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### Author:  [@Kent\_Clark](https://boards.straightdope.com/u/Kent_Clark)
#### Post date: [August 26, 2010, 12:55am UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/11 "2010-08-26T00:55:04Z")
> [@Si\_Amigo](#):
>
> I just had a confortation with my GF over whether or not to put the PB in the fridge because I kinda freaked out on her when she did just that. Thank god that Jiffy actually puts on thier packaging that no refrigiration is required after opening or we would have had an ongoing battle consisting of the movement of the PB from in and out of the fridge over a long period of time until I just gave up and stopped eating PB.
Back when I was a kid in Texas in the days before air conditioning we regularly had peanut butter go rancid, even with three kids in the house. Ever since then I’ve habitually kept open jars in the refrigerator, despite knowing that a) we have air conditioning and b) peanut butter preservatives are better than they were 50 years ago.
But after a few decades, you get used to digging a cold, solid lump of pb from a jar, so it’s all good.
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### Author:  [@GiantRat](https://boards.straightdope.com/u/GiantRat)
#### Post date: [August 26, 2010, 1:25am UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/12 "2010-08-26T01:25:10Z")
> [@beowulff](#):
>
> I may never “rot” or get moldy, but it does get rancid. I’ve never tried to see how long it stays edible, but it’s probably around a year, maybe less.
Oh no! Not another “rancid vs. rotten” thread!!:eek:
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### Author:  [@Derleth](https://boards.straightdope.com/u/Derleth)
#### Post date: [August 26, 2010, 5:08am UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/13 "2010-08-26T05:08:34Z")
> [@GiantRat](#):
>
> > [@beowulff](#):
> >
> > I may never “rot” or get moldy, but it does get rancid. I’ve never tried to see how long it stays edible, but it’s probably around a year, maybe less.
>
> Oh no! Not another “rancid vs. rotten” thread!!:eek:
I’m more concerned about people suddenly getting so interested in precisely how long they can keep various foods.
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### Author:  [@Siam\_Sam](https://boards.straightdope.com/u/Siam_Sam)
#### Post date: [August 26, 2010, 5:50am UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/14 "2010-08-26T05:50:43Z")
We buy Skippy brand, and the jar we have right now says it was manufactured on March 3, 2010 and expires on June 3, 2011. So that’s 15 months anyway.
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### Author:  [@Smeghead](https://boards.straightdope.com/u/Smeghead)
#### Post date: [August 26, 2010, 12:06pm UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/15 "2010-08-26T12:06:53Z")
> [@Siam\_Sam](#):
>
> We buy Skippy brand, and the jar we have right now says it was manufactured on March 3, 2010 and expires on June 3, 2011. So that’s 15 months anyway.
You can pretty much just ignore that. They have to print a sell-by date, and it often bears little to no relation to scientific fact.
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### Author:  [@Siam\_Sam](https://boards.straightdope.com/u/Siam_Sam)
#### Post date: [August 27, 2010, 1:27am UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/16 "2010-08-27T01:27:22Z")
> [@mcgato](#):
>
> I work for Skippy (among other products). The main reason peanut butter goes bad is that the oil in it oxidizes. In a sealed jar, the amount of oxidation should be minimal, so it should last a long time in a sealed jar. I think that the current plastic jars do allow some oxygen to get in over time, so it won’t last forever. I think the current shelf life on the label is 14 or 18 months, which is what testing indicates is about when the aged peanut butter is noticeably different from fresh peanut butter. There’s a recent thread about butter going bad, and most of that discussion also applies to peanut butter.
> [@Smeghead](#):
>
> > [@Siam\_Sam](#):
> >
> > We buy Skippy brand, and the jar we have right now says it was manufactured on March 3, 2010 and expires on June 3, 2011. So that’s 15 months anyway.
>
> You can pretty much just ignore that. They have to print a sell-by date, and it often bears little to no relation to scientific fact.
Hmmm. Those appear to be contradictory.
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### Author:  [@jpbtoothdoctor](https://boards.straightdope.com/u/jpbtoothdoctor)
#### Post date: [February 20, 2015, 3:00am UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/17 "2015-02-20T03:00:48Z")
Recently (Feb 2015) I have had the task of emptying my 93 year old aunt’s hoarder home. I found two unopened jars of Skippy Peanut butter that had a sell by date of Sept 1983!! Yes, 1983!!! Written in pencil was the date purchased by my aunt of July 1982.
Out of curiosity I had to open these jars. Amazingly when opened they smelled fresh and had no visible signs of going bad or rancid. The jars were glass with metal lids. No paper seals like we have now. No I did not have the slightest notion to eat any of it. But the fact that it looked and smelled like it was a new jar made me wonder if it really was a good thing to be eating in the first place (processed peanut butter that is).
Anybody have a jar of Skippy that is older than my aunt’s 32 year old jar? :smack:
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### Author:  [@Duckster](https://boards.straightdope.com/u/Duckster)
#### Post date: [February 20, 2015, 4:01am UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/18 "2015-02-20T04:01:48Z")
\
I have a 15-year old opened, but untouched, jar of Vegemite on my desk at work. It shows no signs of deterioration, and the fragrance is as strong as ever.
\
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### Author:  [@johnpost](https://boards.straightdope.com/u/johnpost)
#### Post date: [February 20, 2015, 4:10am UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/19 "2015-02-20T04:10:03Z")
zombie or no
things don’t have to be filled with toxins to not spoil.
if you do things like prevent oxygen, prevent moisture you could keep things from spoiling.
also with natural peanut butter some people keep that with the jar inverted, that also can make rehomogination easier.
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### Author:  [@TriPolar](https://boards.straightdope.com/u/TriPolar)
#### Post date: [February 20, 2015, 4:15am UTC](https://boards.straightdope.com/t/shelf-life-of-peanut-butter/551427/20 "2015-02-20T04:15:43Z")
> [@Duckster](#):
>
> \
>
> I have a 15-year old opened, but untouched, jar of Vegemite on my desk at work. It shows no signs of deterioration, and the fragrance is as strong as ever.
>
> \
After enough time, maybe centuries, Vegemite turns good.
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