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Rancid


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#1 KingLear

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Posted 14 January 2009 - 10:43 PM

I thought for my first post that I'd ask the greater collective to comment on something that has puzzled me - how long does it really take certain foods to go rancid?

For example - nuts. I have read again and again that nuts should be refrigerated or frozen. Even though I freeze raw pine nuts, since I typically buy tons at a time, I keep at least 10-12 types of nuts in my pantry - walnuts, cashews, pistachios, peanuts, almonds, pecans, etc. Some have been there for months - perhaps years. Not yet have I had a situation where I tasted one and went "yechhh, that's rancid!". Stale, perhaps, but not rancid.

Similar situation with butter. "Never keep it on the counter" we are told. Yet I do - have all my life - and have yet discovered rancid butter in the dish on my counter. I couldn't pick the taste of rancid butter out of a lineup. In the summer, it might go a bit yellow, but it never acquires an off taste. Mind you, we only put out about a stick at a time, but it still takes a few days to get through that much room temperature butter. Even with the butter I make from scratch, it's the same story.

Last year, I made a chicken confit - chicken thighs cooked for 12 hours at 200° F in olive oil. After it cooled, I poured the oil, which contained chicken fat by that point, into a jar. It lasted in my fridge for 10 months - not that it went bad, rather I just finally finished it after that amount of time. Given what I have read online, it should have turned long before I used up the last of it.

In a somewhat similar vein (even though it's not a fat) - wine - I love it, I drink it every day. I try a wide assortment from all over the world. Unfortunately, I still can't tell a tainted wine from a wine that simply tastes bad. I may have had a rancid wine, but I more than likely considered it not a good beverage, as opposed to an off one.

Just in case you're wondering, I'm told that I do have a good palette, so I don't think it's just me. I have queried friends and family about this topic - no one seems to be able to definitively describe what rancid really means.

So there you go - I'd love to hear about peoples' experiences with rancid. Is it easy to predict, to taste, to see? Is rancid a matter of degree or is it an absolute?

#2 muichoi

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Posted 15 January 2009 - 01:37 AM

I think in the case of butter you're just used to the rancid taste-and actually nearly all salted butter tastes rancid anyway.

#3 stuartlikesstrudel

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Posted 15 January 2009 - 01:52 AM

I have definitely had rancid nuts before. Usually walnuts, I think... they take a bitter, unpleasant taste. Not inedible, but not something I would use in cooking or for snacking on.

But I still don't refrigerate nuts, and very rarely have I had to throw them out.

#4 Starkman

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Posted 15 January 2009 - 08:53 AM

Okay, so does "rancid" mean spoiled, as in you can get sick from it, or does it just mean chemically changed, as in wine in a bottle that's been sitting around for five days?

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#5 KingLear

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Posted 15 January 2009 - 08:36 PM

Great question - I don't know the answer. Interesting that no one yet can describe what a rancid walnut or what rancid butter tastes like. Despite all the warnings out there on the interweb, no one reading or posting to this thread yet has had the experience.

#6 Qwerty

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Posted 15 January 2009 - 08:42 PM

Rancid to me implies that it would be inedible. If something were slightly or just beginning to spoil I would call it "off."

If something is truly rancid odds are 99% of people would know due to smell and taste.

I don't think room temp. butter is a problem. If left out for weeks maybe but I've always understood that butter was fairly stable at room temp.

#7 KingLear

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Posted 15 January 2009 - 08:48 PM

Interesting that no one yet can describe what a rancid walnut ...

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Sorry - other than stuartlikesstrudel.

#8 Pam R

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Posted 15 January 2009 - 09:11 PM

Rancid to me implies that it would be inedible. If something were slightly or just beginning to spoil I would call it "off."

If something is truly rancid odds are 99% of people would know due to smell and taste.

Absolutely. When you open a bottle of nut oil that's rancid, you'll know. The smell will hit you fast. If you taste a rancid walnut, you'll know it and most likely wish to spit it out and throw out the bag.

#9 Chris Hennes

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Posted 15 January 2009 - 09:19 PM

Fat that has gone rancid has a very distinct smell, and it seems to be the same (or very similar) across any fat I have ever experienced it with. Various fats seem to hold up better than others, but eventually they will all go: the effect is exaggerated by exposure to heat, and I am told light as well, though I don't know that from personal experience.

I can call the smell to mind, but I don't quite know how to describe it: it's pungent, funky, musty, and just generally nasty. You really can't mistake it. And if you taste it, you'll know for sure. My taste buds are cringing right now just thinking about it...

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#10 paulraphael

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Posted 15 January 2009 - 09:22 PM

Rancid to me implies that it would be inedible.


No, rancid has a specific definition ... it's a particular kind of spoilage. In general the effect of rancidity is less dramatic than the word, so people consume rancid stuff all the time.

Rancidity is spoilage due to oxidation of fats. It has nothing to do with microbes. The process is slowed but not halted by freezing. Polyunsaturated oils rancidify most quickly (fish oil, canola oil); saturated fats least quickly (pork fat, butter). Monounsaturated fats are somewhere in between (olive oil, etc.).

If you've ever noticed cooking oil or butter that smelled a bit like stale nuts, that's rancidity.

It won't usually taste so bad that you spit it out; it just won't taste good. It won't make you sick, at least not accutely. Rancid fats are high in free radicals, which may have bad longterm health effects, but you won't get any kind of food poisoning from them.

#11 Pam R

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Posted 15 January 2009 - 09:27 PM

It won't usually taste so bad that you spit it out; it just won't taste good.

A rancid walnut might be bad enough to make you spit it out. I have.

#12 Qwerty

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Posted 15 January 2009 - 09:32 PM

I suppose inedible may have been the wrong term, but my intention was to say that you would almost certainly know if something was rancid--would you not? While not technically inedible it would be rendered inedible due to our sense of smell and taste.

#13 Chris Hennes

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Posted 15 January 2009 - 09:34 PM

No, rancid has a specific definition ... it's a particular kind of spoilage. In general the effect of rancidity is less dramatic than the word, so people consume rancid stuff all the time.

It's important to remember that as Paul points out, "going rancid" is a process that takes time. It's not like one day your oil is perfect and the next it's gone. It gets more and more rancid as time goes on. Stuff that's only a little rancid may be tolerable, but believe me, if it's really rancid, it's definitely not "less dramatic than the word" and you will spit it out. Truly gross. Find a can of vegetable shortening, unseal it, and leave it in your cupboard for three years. When you open it, you will understand rancidity. Personal experience.

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#14 C. sapidus

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Posted 15 January 2009 - 10:13 PM

Our high school chemistry class made esters with n-butyric acid (clicky), the compound that gives rancid butter its distinctive foul odor. The rancid butter stench traveled from the chemistry lab, down the stairwell, and into the cafeteria. This made lunch period pretty unpleasant for a few days each year. Amazingly, butyric acid esters have lovely, fruity aromas. Ahh, fun with chemistry.

I had the dubious pleasure of smelling n-butyric acid once before high school. We moved when I was in middle school, and the previous homeowner had forgotten to empty the butter tray before turning off the refrigerator. The house must have remained empty for many weeks because opening the refrigerator door released a memorable stench.

I seriously doubt that anyone not afflicted with anosmia would have eaten that particular stick of butter.

#15 KingLear

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Posted 15 January 2009 - 10:14 PM

Now we're talking! Thanks to paulraphael and Chris Hennes. I was indeed hoping to read that rancidity is a matter of degree rather than an absolute. After reading the last couple of posts, the image that comes to mind is that of a dishcloth. After a couple of days, there is an odor that is less than fresh. A couple of days later, the smell is a bit off. A couple of days after that, you'll turn your head in disgust at the smell. I guess that encapsulates rancidity.

The reason I started the thread in the first place was because I wanted to start to understand how some people define rancidity as opposed to simply smells/tastes that are not favorable to them. My wife recoils at the smell of my homemade sauerkraut, yet my teenage son can't wait for a Rueben. But the same son wouldn't touch fromage bleu, whereas my wife can't get enough. However, if I make a fromage fort that includes bleu cheese, my son can't stop eating it when I open the jar. Some people would consider cultured butter to be rancid, but many would be drooling at the notion.

Anyhoo, it's an interesting discussion of taste - what may be one's garbage is another's gold.

#16 JasmineL

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Posted 15 January 2009 - 10:46 PM

I had the dubious pleasure of smelling n-butyric acid once before high school. We moved when I was in middle school, and the previous homeowner had forgotten to empty the butter tray before turning off the refrigerator. The house must have remained empty for many weeks because opening the refrigerator door released a memorable stench.

I seriously doubt that anyone not afflicted with anosmia would have eaten that particular stick of butter.

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This happened to me. It took me ages to get the smell out of the refrigerator. It makes me heave just thinking about it.

#17 paulraphael

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Posted 15 January 2009 - 11:02 PM

"going rancid" is a process that takes time. It's not like one day your oil is perfect and the next it's gone. It gets more and more rancid as time goes on. Stuff that's only a little rancid may be tolerable, but believe me, if it's really rancid, it's definitely not "less dramatic than the word" and you will spit it out.


That's a good point. In my experience, things rarely get to that point. The freezer is the only place I might forget food for a period of months, but well wrapped in that environment food takes a lot longer than that to go disgustingly rancid.

Nuts and oils and butter are the most common culprits. They usually don't get much past the iffy stage before they get tossed.

One counterintuitive tip: salt speeds rancidification. Even though it acts as a preservative against microbes, it speeds oxidation of fats.

Edited by paulraphael, 15 January 2009 - 11:06 PM.


#18 Chris Hennes

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Posted 16 January 2009 - 08:37 AM

Some people would consider cultured butter to be rancid, but many would be drooling at the notion.

Again, as paulraphael pointed out above, in the culinary world the word "rancid" means something very specific. It is not a "catch-all" term for something that one doesn't like, it refers to a specific type of spoilage. So, cultured butter may be distasteful to some, but in the sense that we are discussing rancidity here, it is not rancid (well, at first! of course it can turn rancid like any other fat). I promise you, the best way to understand rancidity is to find something rancid and smell it. You will forever be able to detect its presence, even in smaller quantities. It is a specific and distinctive smell that is not just "ooh, I don't like that smell," it's "ooh, that's rancid."

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#19 KingLear

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Posted 16 January 2009 - 11:31 PM

I promise you, the best way to understand rancidity is to find something rancid and smell it. You will forever be able to detect its presence, even in smaller quantities. It is a specific and distinctive smell that is not just "ooh, I don't like that smell," it's "ooh, that's rancid."

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Chris - I completely agree with your assessment, however the general population would think of rancid as having a much broader definition. Here are a few examples from dictionary.reference.com:

1. having a rank, unpleasant, stale smell or taste, as through decomposition, esp. of fats or oils: rancid butter.
2. (of an odor or taste) rank, unpleasant, and stale: a rancid smell.
3. offensive or nasty; disagreeable.

1. (used of decomposing oils or fats) having a rank smell or taste usually due to a chemical change or decomposition; "rancid butter"; "rancid bacon"
2. smelling of fermentation or staleness [syn: sour]

As you can see, by definition, rancid can simply mean an offensive, fermented or stale odor. In culinary terms, those definitions are too broad, but for the general population, rancid is anything that is simply unpleasant.

Edited by KingLear, 16 January 2009 - 11:32 PM.