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View Full Version : Olive oil turns to trans fat if heated past smoke point???



adrianna!!
02-02-2006, 04:19 PM
Just saw this on another message board, and I do not think it is correct. But alas, I have no way to prove it. Do any of you smart BBers know of a site that explains why this is not possible?

Or *IS* it possible????? :confused: The poster said that all oils turn to trans fat when heated too high. I thought you had to do some hydrogenating process to the oil to make it a trans fat. Please advise!

GingerPow
02-02-2006, 04:27 PM
I don't know if this is to be considered the final authority, but I found this:

"3. AVOID BURNING OR OVERCOOKING OF FATS
Typical frying temperature is about 400 degrees F and can reach up to 600-700 degrees F. When fats/oils are heated to such temperatures the CIS fatty acids are converted to TRANS fatty acids. This simply pertains to how the molecule is turned but the consequence is that unsaturated fats begin to behave like saturated fats with respect to their effects in raising instead of lowering serum cholesterol levels (about 50% of the cholesterol increasing effect of saturated fat) and can raise LDL cholesterol by nearly as much as the saturated fat (Mensink & katan, 1990). Besides the extra fat consumed, this is another reason why fried foods are more likely to contributes to a hardening of the arteries. Also, partially hydrogenated vegetable oils can vary in their TRANS isomer content from 5% to 45%.

When fat is reheated to frying temperatures a second time (as in deep fryers) the fat is more likely to develop cancer the producing agent acrolein and even benzopyrene (one of the most potent carcinogens known).

Very hot temperature also destroy certain vitamins and may alter the major proteins.

Hence, baking is preferable to frying since here the commonly used temperature is 350 degrees F.

Burning produces charring products that are carcinogenic. If one is quick frying and burning occurs, temperatures up to 1000 degrees F could have been reached. Even if one does not burn the oil or fat, overcooking (esp. when one reuses oils) breaks down the polyunsaturated molecule and free radicals can form. These are fragments that have combined with any available oxygen to produce toxic peroxides. They are toxic because that act as strong oxidizing agents that damage and destroy cells.

Now, for a practical solution. One actually doesn't need to fry with oil, water will suffice as long as one uses a good stainless steel frying pan and stirs more frequently. This is a trick I picked up from one of Pritikin's books; a book useful for such advice as to how to use less oil. For instance, a very good recipe for making some very tasty chips produced without deep frying or any oils whatsoever is to be found there."

http://www.efn.org/~sundance/fats_and_oils.html

sneezles
02-02-2006, 05:00 PM
Interesting article, Gingerpow. Thanks for sharing.

I've always thought the oil was damaged and released free radicals which then increase your C-Reactive Protein and cause inflammation and raise your LDL. This is the first I"ve heard of it actually becoming a trans fatty acid.

Maybe Ana will know something!

DmOrtega
02-02-2006, 05:06 PM
Would a typical stir-fry, med-high, fall into the 400+ degree range?

wallycat
02-02-2006, 05:20 PM
From one website:
"The large refinery-like factories which take unsaturated vegetable oil and turn it into margarine or vegetable lard do so by bubbling hydrogen gas through 250 to 400 degree hot vegetable oil in the presence of a metal catalyst, usually nickel or platinum. The process can take several hours. You cannot make a saturated product like margarine at home by heating olive oil or any other vegetable oil in a pan."

Yes, oil changes when you heat it (molecules move around...that is the nature of heating and cooling) but NO, you cannot, to any degree, hydrogenate your oils into trans fats unless you have a huge basement and a big lab down there :D :p

dorothyntototoo
02-02-2006, 05:34 PM
GingerPow, I wouldn't consider this person's information "the final authority". The writing seems to ramble & is full of typos - to me a giveaway that it's an amateur. Oil used for frying is usually about 360 degrees. At 1000 degrees you'd burn your house down. Those interested in this topic might want to do more research. There's alot of junk out there on the www. ;)

GingerPow
02-02-2006, 06:56 PM
GingerPow, I wouldn't consider this person's information "the final authority". The writing seems to ramble & is full of typos - to me a giveaway that it's an amateur. Oil used for frying is usually about 360 degrees. At 1000 degrees you'd burn your house down. Those interested in this topic might want to do more research. There's alot of junk out there on the www. ;)
No question about that - it wasn't from a research or university website. That's why I stated that "I don't know if this should be considered the final authority" as kind of a disclaimer of my own. I didn't find a plethura of info on that question (that may be an indicator right there). Who knows, maybe it's the next urban myth/internet rumor? How many of THOSE are circulating these days? :rolleyes:

Here's one that I read about a couple years ago, and actually stopped buying canola oil because of it. (I'm buying it again now). This is the Snopes.com link disputing the internet rumor.
http://www.snopes.com/medical/toxins/canola.asp

adrianna!!
02-03-2006, 05:50 AM
Wow! LOL...I did not get any email notifications for this thread, so i assumed no one had answered! I did some more research and came up with this...

Olive Oil Myth: Heating a cooking oil will make it saturated or a trans-fatty oil.

The Facts: As far as making a saturated fat, according to Dr. A. Kiritsakis, a world renowned oil chemist in Athens, (Book - OLIVE OIL FROM THE TREE TO THE TABLE -Second edition 1998), all oils will oxidize and hydrogenate to a tiny degree if repeatedly heated to very high temperatures such as is done in commercial frying operations. Olive pomace oil and virgin olive oil are both highly monounsaturated oils and therefore resistant to oxidation and hydrogenation. Studies have shown oxidation and hydrogenation occurs to a lesser degree in olive oil than in other oils. But in any case, the amount of hydrogenation is miniscule and no home cook would ever experience this problem.

The large refinery-like factories which take unsaturated vegetable oil and turn it into margarine or vegetable lard do so by bubbling hydrogen gas through 250 to 400 degree hot vegetable oil in the presence of a metal catalyst, usually nickel or platinum. The process can take several hours. You cannot make a saturated product like margarine at home by heating olive oil or any other vegetable oil in a pan. We don't know where this weird notion has come from. For more see our olive oil chemistry page

Changing a cis-fat to a trans-fat does not occur on a home stove

adrianna!!
02-03-2006, 05:52 AM
http://www.oliveoilsource.com/cooking_olive_oil.htm

forgot to post the source!

Thanks for the replies, it is an interesting topic.