high temperature Olive Oil: issues?

Does olive oil (organic extra virgin) de-stabilise and become a transfat when it is heated to a high temperature (like roasting potatoes)?

i think grapeseed oil is more stable for higher temp cooking. i have also heard that adding rosemary to cooking oil (during cooking) helps the oil remain stable for a longer time.

Not according to the Olive Oil Police...

Olive Oil Source: Cooking with Olive Oil
http://www.oliveoilsource.com/cooking_olive_oil.htm

"Trans Fatty acids: Olive oil has no trans fatty acids. When an oil
is partially hydrogenated it can be in the cis or trans conformation
which refers to which side of the fatty acid double bond the hydrogen
is on. Olive oil is not a trans fatty acid because it has not been
partially hydrogenated in a factory to make it solid at room
temperature like margarine has. Trans fat is created by bubbling
hydrogen 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 accidentally make trans or saturated fatty
acids at home on your range when heating olive oil or other oils."

Superb Eric, just what I needed to know. I'm wondering if 'de-stabilising' is the same thing as lots of places seem to say that olive oil shouldn't be heated to a high temperature but I'm off to that source you quoted to have a look.

Kelson, I just love rosemary in the oil even if not cooking with it. I could even 'smell' rosemary when I read your post

As far as I know, high heat wrecks EVO's health properties and flavour, but I haven't heard about it becoming actually harmful.

From what I read when researching use and seasoning of cast iron cookware you don't want an oil to reach it's "smoke point" (temperature) when cooking if you can avoid it - it changes state and creates some carcinogenic compounds. I have hopefully attached a small spreadsheet of the smoke points of various oils that I copied from one of the sites I visited last year; unfortunately I don't have any recollection or record of what site but I think a quick google will confirm or correct the info. The names of the oils seem less than exact but generally the more highly refined an oil the higher the smoke point. (After the site refused to accept any file formats or extensions I could come up with, including plain text, I'll just paste the list here.)


Fat Smoke Point °F Smoke Point °C

Unrefined canola oil 225°F 107°C
Unrefined flaxseed oil 225°F 107°C
Unrefined safflower oil 225°F 107°C
Unrefined sunflower oil 225°F 107°C
Unrefined corn oil 320°F 160°C
Unrfned high-oleic sunflwr oil 320°F 160°C
Extra virgin olive oil 320°F 160°C
Unrefined peanut oil 320°F 160°C
Semirefined safflower oil 320°F 160°C
Unrefined soy oil 320°F 160°C
Unrefined walnut oi 320°F 160°C
Hemp seed oil 330°F 165°C
Butter 350°F 177°C
Semirefined canola oil 350°F 177°C
Coconut oil 350°F 177°C
Unrefined sesame oil 350°F 177°C
Semirefined soy oil 350°F 177°C
Vegetable shortening 360°F 182°C
Lard 370°F 182°C
Macadamia nut oil 390°F 199°C
Refined canola oil 400°F 204°C
Semirefined walnut oil 400°F 204°C
H-qlty(lw acdity)xtr-vrgn olive 405°F 207°C
Sesame oil 410°F 210°C
Cottonseed oil 420°F 216°C
Grapeseed oil 420°F 216°C
Virgin olive oil 420°F 216°C
Almond oil 420°F 216°C
Hazelnut oil 430°F 221°C
Peanut oil 440°F 227°C
Sunflower oil 440°F 227°C
Refined corn oil 450°F 232°C
Palm oil 450°F 232°C
Palm kernel oil 450°F 232°C
Refined high-oleic sunflwr oil 450°F 232°C
Refined peanut oil 450°F 232°C
Refined Safflower oil 450°F 232°C
Semirefined sesame oil 450°F 232°C
Refined soy oil 450°F 232°C
Semirefined sunflower oil 450°F 232°C
Olive pomace oil 460°F 238°C
Extra light olive oit 468°F 242°C
Soybean oil 495°F 257°C
Safflower oil 510°F 266°C
Avocado oil 520°F 271°C



Rufus

I believe the stability of olive oil relates to it maintaining surface tension. Olive is not a good frying oil because prolonged high heat breaks it down and food more or less boils in it. However, I have had great success roasting potatos , beets , garlic in olive oil and the food browns nicely. But the " boiling in oil " tendency in olive oil cooking is used to advantage. I make a few Lebanese/Syrian dishes which utilize this effect wonderfully. One dish is called lubi-be-zeit{spelling is phonetic} . It is beans in oil. Whole green beans are sauteed in a lot of olive oil with a little minced onion and garlic until semi soft. Then a bit of tomato paste is added and it is simmered until soft. A little more oil can be added along the way. So , rather than browning and forming a crust the beans and oil sort of infuse into each other , the oil becomes the base of a sauce. With heavier oils , butter , lard you would just have gobs of oil floating to the top of your dish. I cook similar dishes with eggplant , lamb , or peppers. By the way , the beans in oil are wrapped in flat bread. Can't wait till summer. When it comes to olive oil - local shmokal. I will buy it no matter where I live.

Hi all,
I'm chad.
I read that organic olive oil alters its molecular composition only between 210-220 ° C.

No—organic extra virgin olive oil does not turn into trans fat when heated, even at typical cooking or roasting temperatures. While heating can reduce some of its beneficial compounds and, if overheated past its smoke point, may cause it to break down in quality, it doesn’t convert into trans fats. So roasting potatoes with a good-quality oil like Redstone Olive Oil is still a safe choice, as long as it’s not heated excessively beyond its smoke point.