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Author Topic: Does peanut butter ever go bad?
Myshkin
The First USA Noel


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(I don't know whether this belongs in Food or Science, but I am more curious about the science than about the food itself.)

Not only have a never heard of any "bad" peanut butter, but recently I found a squeeze tube of peanut butter that I filled for a camping trip some 25 years ago. I remember because I borrowed the tube from my High School GF. Now, it is possible that I re-filled it somewhere along the way, but I cannot recall using this tube in at least the last 10-15 years. It looks good. It smells good. So I ate some and I'm not dead yet. It tasted like peanut butter. This tube was not "sealed", just sort of closed.

PB has significant amounts of all three major foodstuffs: carbs, oils, and protein. It should support microbes, should it not? It is not dried or canned. It is not pre-rotted (so to speak) like cheese or some pickles. It does not have a pH that would tend to prevent microbial growth. I have two jars of BP on my shelf, and neither lists a preservative as an ingredient.

Can microbes be grown on a peanut butter medium?

Posts: 741 | From: Big Bend, Texas | Registered: May 2004  |  IP: Logged | Report this post to a moderator
TrekkerScout
Deck the Malls


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Peanut butter typically does not support bacteria and/or mold growth because of its low moisture content (less than 1%) and high oil content. However, the oils can become rancid over time. When peanut butter become rancid, it develops an odd, oily flavor and odor. There are several factors that contribute to the time it takes for peanut butter to become rancid (i.e temperature, additives, oxygen availability). Basically, if it still tastes and smells okay, its probably still safe to consume, but most peanut butters start to turn rancid after 9 to 12 months under normal conditions.
Posts: 306 | From: Tacoma, WA | Registered: Sep 2005  |  IP: Logged | Report this post to a moderator
Giant Communist Robot
I Saw Three Shipments


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I'd guess it needs some exposure to air. Then the oil would go rancid and the flavor would be "off." Peanut butter doesn't require refrigeration--I have never heard of microbes spoiling it.

Just a guess.


...

Posts: 63 | From: Aiea, Hawaii | Registered: Jul 2005  |  IP: Logged | Report this post to a moderator
qualli
We Wish You a Merry Giftmas


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I did have a jar of peanut butter once that, for lack of better word, settled. There was an oily pool on top of the peanut butter. It had been opened though.

Peanut Butter and Jelly together in a jar starts going "funky" faster than just plain peanut butter

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Posts: 820 | From: North Carolina | Registered: Nov 2004  |  IP: Logged | Report this post to a moderator
Myshkin
The First USA Noel


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If I understand it correctly, the "rancidization" of oils is an abiotic process. It is not a metabolism of the oil by microbes. The rancid odor and flavor are aldehydes and ketones that are derived from radical oxidation of hydrocarbons.
Chemogenesis web book

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Gezal
I'm Dreaming of a White Sale


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I did not find anything on old penut butter but there is something on oatmeal from the 70s:

http://www.wired.com/news/business/0,1367,69447,00.html

Here is aquote from this article:

"Such are the findings of food science researchers who recently subjected a panel of human tasters to samples of really old food. They discovered that artifacts like 20-year-old dried milk and 28-year-old rolled oats were still perfectly edible and sometimes even tasted OK."

I had some vintage packets of Kool-aid about five years ago, I don't know how old they were but they were made before ZIP codes. I mixed one up, an orange one, it tasted like Kool-aid.

I also had a tin of Borden chocolate milk powder that had a 1948 copyright date on it. Although the powder had settled into a dense hard block in the bottom half of the can it smelled fine -- like chocolate powder. I didn't try that one but it would probably be OK.

I did notice that the taste study of the old oatmeal was done at Brigham Young University. I remember the Mormons tended to be into surviving nuclear war and Y2K -- I suppose they have found some other reason to store things in their basement these days.

Has anyone ever eaten any falloutshelter food? Or do you know someone who has?

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TheBobo
Markdown, the Herald Angels Sing


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I once had peanut butter assault my jar of Hellmans in the fridge.
So to answer your question-yes peanut butter can go bad.

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Posts: 2474 | From: Scranton, PA | Registered: Apr 2003  |  IP: Logged | Report this post to a moderator
USA-Mick66
I'll Be Home for After Christmas Sales


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Oh yes....

I can still taste it 5 years later..... [Eek!]

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Sasquatch
I'm Dreaming of a White Sale


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A friend bought one of those old decommissioned nuclear missile silos (Atlas I think?) and it still had some food stores in it. Squarish 5 gallon metal cans with survival crackers with a 1957 date, and sardine can sized tins of almonds. We opened and ate some of the crackers just because, there was a very slight rancid odor from the cans, but the crackers individually smelled and tasted fine. The almonds however, had sort of crytallized, and corroded the cans, we didn't sample those.
Posts: 30 | From: Kansas | Registered: Sep 2005  |  IP: Logged | Report this post to a moderator
quiltsbypam
Happy Holly Days


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Peanut butter will keep for a really, really long time. If it separates, just stir it back up. That's what you have to do with organic peanut butter, anyway; even when it's fresh.

PB can survive some extreme conditions. One time when I was a kid, we were driving somewhere on vacation (I don't remember where now), but we stopped for a tailgate picnic. It was a really hot day and, when Mom made the sandwiches, she poured the PB on the bread. Aside from looking like baby poopy, it still tasted fine. And since that was before McDonald's was common, we didn't question it. We just ate and then finished our drive to our vacation spot. The Adirondacks, probably. And none of us got sick.

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"No Biblical hell could ever be worse than the state of perpetual inconsequence." Beatrice in Dangerous Beauty

Posts: 1816 | From: Cayuga County, NY | Registered: Nov 2005  |  IP: Logged | Report this post to a moderator
   

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