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  #1  
Old 08-25-2010, 01:20 PM
Captain Midnight Captain Midnight is offline
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Shelf life of peanut butter..............

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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  #2  
Old 08-25-2010, 01:29 PM
beowulff beowulff is offline
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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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  #3  
Old 08-25-2010, 01:31 PM
mcgato mcgato is offline
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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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  #4  
Old 08-25-2010, 02:14 PM
Smeghead Smeghead is offline
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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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  #5  
Old 08-25-2010, 02:48 PM
dracoi dracoi is offline
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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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  #6  
Old 08-25-2010, 02:55 PM
Si Amigo Si Amigo is offline
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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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  #7  
Old 08-25-2010, 03:21 PM
Smeghead Smeghead is offline
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Quote:
Originally Posted by dracoi View Post
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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Old 08-25-2010, 05:05 PM
dracoi dracoi is offline
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Originally Posted by Si Amigo View Post
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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  #9  
Old 08-25-2010, 05:17 PM
t-bonham@scc.net t-bonham@scc.net is offline
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Peanut butter also contains a fair amount of salt, which should help to preserve it.
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  #10  
Old 08-25-2010, 06:21 PM
mcgato mcgato is offline
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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.

Last edited by mcgato; 08-25-2010 at 06:22 PM..
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  #11  
Old 08-25-2010, 07:55 PM
kunilou kunilou is offline
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Quote:
Originally Posted by Si Amigo View Post
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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  #12  
Old 08-25-2010, 08:25 PM
GiantRat GiantRat is offline
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Originally Posted by beowulff View Post
I may never ďrotĒ or get moldy, but it does get rancid. Iíve never tried to see how long it stays edible, but itís probably around a year, maybe less.
Oh no! Not another "rancid vs. rotten" thread!!
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  #13  
Old 08-26-2010, 12:08 AM
Derleth Derleth is offline
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Quote:
Originally Posted by GiantRat View Post
Quote:
Originally Posted by beowulff View Post
I may never ďrotĒ or get moldy, but it does get rancid. Iíve never tried to see how long it stays edible, but itís probably around a year, maybe less.
Oh no! Not another "rancid vs. rotten" thread!!
I'm more concerned about people suddenly getting so interested in precisely how long they can keep various foods.
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  #14  
Old 08-26-2010, 12:50 AM
Siam Sam Siam Sam is offline
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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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  #15  
Old 08-26-2010, 07:06 AM
Smeghead Smeghead is offline
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Originally Posted by Siam Sam View Post
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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  #16  
Old 08-26-2010, 08:27 PM
Siam Sam Siam Sam is offline
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Quote:
Originally Posted by mcgato View Post
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.
Quote:
Originally Posted by Smeghead View Post
Quote:
Originally Posted by Siam Sam View Post
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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  #17  
Old 02-19-2015, 09:00 PM
jpbtoothdoctor jpbtoothdoctor is offline
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Lasts Forever Perhaps

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?
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  #18  
Old 02-19-2015, 10:01 PM
Duckster Duckster is offline
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<hijack=slight>

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.

</hijack>
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  #19  
Old 02-19-2015, 10:10 PM
johnpost johnpost is online now
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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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  #20  
Old 02-19-2015, 10:15 PM
TriPolar TriPolar is offline
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Originally Posted by Duckster View Post
<hijack=slight>

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.

</hijack>
After enough time, maybe centuries, Vegemite turns good.
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  #21  
Old 02-21-2015, 03:35 PM
Hari Seldon Hari Seldon is online now
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I used to get PB from a health food store that had a grinder. You put nuts in the hopper, put your container underneath, turned the switches and out came fresh PB. We always kept it in the fridge and, kept that way, it never separated and didn't get rancid in a couple years, anyway. Sadly the store closed at least ten years ago.
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  #22  
Old 02-21-2015, 06:48 PM
t-bonham@scc.net t-bonham@scc.net is offline
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Originally Posted by Hari Seldon View Post
I used to get PB from a health food store that had a grinder. You put nuts in the hopper, put your container underneath, turned the switches and out came fresh PB. We always kept it in the fridge and, kept that way, it never separated and didn't get rancid in a couple years, anyway. Sadly the store closed at least ten years ago.
Can't you just use any good food processor or blender to do this at home?
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  #23  
Old 02-21-2015, 10:12 PM
HoneyBadgerDC HoneyBadgerDC is online now
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I have a jar in my shop that I only occassionaly use. My guess is a minimum of 4 years old. I have to stir it up every time I use it as the oil sperates. I maybe use it only a couple of times a year. Las time I used it the lid was not as tight as it should have been and I almost trashed it but the smell was fine after stirring.
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  #24  
Old 02-22-2015, 02:16 AM
Habeed Habeed is online now
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If you put it in the freezer, that should boost the shelf life enormously, right? This is because the oxidation reaction, which is probably some variant on combustion, needs the reacting species to interact with sufficient energy (and orientation) for the reaction to happen. Lowering the temperature would make only a tiny fraction of all the oil molecules in that jar to ever meet the activation energy criterion, and so the rate should drop nonlinearly to near zero.

Last edited by Habeed; 02-22-2015 at 02:16 AM..
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  #25  
Old 02-22-2015, 10:44 AM
kopek kopek is offline
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Somehow this has brought back the taste of C-rats past. ROTC didn't rate high up the food chain and some of the stuff we got was real vintage. The peanut butter and crackers and spaghetti were the high points.

I think I'll go chainsmoke a couple cigars until the memory flashback leaves my tongue.
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  #26  
Old 02-22-2015, 12:51 PM
GusNSpot GusNSpot is offline
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ARMY, 1961, "C" rations was all I ever got. The canned ham was good as gold for trading. Better than the cigarettes. IIRC
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  #27  
Old 02-22-2015, 01:20 PM
DrDeth DrDeth is online now
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Quote:
Originally Posted by mcgato View Post
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.
Yes, a sealed glass jar of Pnut butter should be edible for quite some time. One reason why for disaster readiness I suggest a case of that and two large boxes of Matzo- those ones that grocery stores sell at a loss-leader for Passover. (I used to suggest Pilot bread aka hardtack, but now that's rare and expensive).
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