The Straight Dope

Go Back   Straight Dope Message Board > Main > General Questions

Reply
 
Thread Tools Display Modes
  #1  
Old 08-25-2010, 01:20 PM
Captain Midnight Captain Midnight is offline
BANNED
 
Join Date: Jun 2010
Posts: 409
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?
Reply With Quote
Advertisements  
  #2  
Old 08-25-2010, 01:29 PM
beowulff beowulff is offline
Member
 
Join Date: May 2001
Location: Scottsdale, more-or-less
Posts: 10,672
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.
Reply With Quote
  #3  
Old 08-25-2010, 01:31 PM
mcgato mcgato is online now
Guest
 
Join Date: Aug 2010
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.
Reply With Quote
  #4  
Old 08-25-2010, 02:14 PM
Smeghead Smeghead is offline
Guest
 
Join Date: Apr 2000
Yep. Same deal as honey and butter. Not enough water for microbial spoilage, so all you have to worry about is oxidative rancidity.
Reply With Quote
  #5  
Old 08-25-2010, 02:48 PM
dracoi dracoi is offline
Guest
 
Join Date: Dec 2008
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.
Reply With Quote
  #6  
Old 08-25-2010, 02:55 PM
Si Amigo Si Amigo is offline
Member
 
Join Date: Nov 2004
Location: North of 8 Mile
Posts: 3,115
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.
Reply With Quote
  #7  
Old 08-25-2010, 03:21 PM
Smeghead Smeghead is offline
Guest
 
Join Date: Apr 2000
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.
Reply With Quote
  #8  
Old 08-25-2010, 05:05 PM
dracoi dracoi is offline
Guest
 
Join Date: Dec 2008
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.
How are you guys doing on the mustard and ketchup?
Reply With Quote
  #9  
Old 08-25-2010, 05:17 PM
t-bonham@scc.net t-bonham@scc.net is offline
Guest
 
Join Date: Mar 2003
Peanut butter also contains a fair amount of salt, which should help to preserve it.
Reply With Quote
  #10  
Old 08-25-2010, 06:21 PM
mcgato mcgato is online now
Guest
 
Join Date: Aug 2010
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..
Reply With Quote
  #11  
Old 08-25-2010, 07:55 PM
kunilou kunilou is online now
Charter Member
 
Join Date: Apr 1999
Posts: 17,365
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.
Reply With Quote
  #12  
Old 08-25-2010, 08:25 PM
GiantRat GiantRat is offline
Guest
 
Join Date: Apr 2006
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!!
Reply With Quote
  #13  
Old 08-26-2010, 12:08 AM
Derleth Derleth is offline
Guest
 
Join Date: Apr 2000
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.
Reply With Quote
  #14  
Old 08-26-2010, 12:50 AM
Siam Sam Siam Sam is offline
Elephant Whisperer
 
Join Date: Nov 2006
Location: Bangkok
Posts: 28,583
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.
Reply With Quote
  #15  
Old 08-26-2010, 07:06 AM
Smeghead Smeghead is offline
Guest
 
Join Date: Apr 2000
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.
Reply With Quote
  #16  
Old 08-26-2010, 08:27 PM
Siam Sam Siam Sam is offline
Elephant Whisperer
 
Join Date: Nov 2006
Location: Bangkok
Posts: 28,583
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.
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 10:57 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.

Send questions for Cecil Adams to: cecil@chicagoreader.com

Send comments about this website to: webmaster@straightdope.com

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Publishers - interested in subscribing to the Straight Dope?
Write to: sdsubscriptions@chicagoreader.com.

Copyright © 2013 Sun-Times Media, LLC.