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Q: Olive Oil Fats Converted Through Cooking or High Heat ( Answered 5 out of 5 stars,   0 Comments )
Subject: Olive Oil Fats Converted Through Cooking or High Heat
Category: Health
Asked by: purrsian-ga
List Price: $15.00
Posted: 05 Jan 2005 15:02 PST
Expires: 04 Feb 2005 15:02 PST
Question ID: 452598
The son of a chef once mentioned that whenever olive oil is used for
cooking that the temperatures being used will convert this
monounsaturated fat into a saturated fat.  I've never heard that
before and am amazed it's not in the natural foods literature.  Can
someone clear this up for me, please?
Subject: Re: Olive Oil Fats Converted Through Cooking or High Heat
Answered By: pinkfreud-ga on 05 Jan 2005 15:43 PST
Rated:5 out of 5 stars
Howdy again, Purrsian!

High temperatures aren't good for any kind of cooking oil, but the
notion that olive oil becomes unhealthful when heated is a myth.

"Elizabeth asks: 
I have recently been informed that when olive oil is heated it creates
a saturated fat as opposed to unsaturated when used directly from the
bottle. It has been recommended that one cook with Canola Oil and use
Olive Oil directly from the bottle for its flavor.

OOS Replies:  
Myth. Heating olive oil will evaporate the alcohols and esters which
make up the delicate taste and fragrance of olive oil. Heating olive
oil will not change its health aspects appreciably. All oils will
oxidize if repeatedly heated to high temperatures. Olive Oil seems to
be more resistant to this. Heating olive oil will not change it from a
monosaturated fat which is considered far healthier than the
polyunsaturated fats in margarine or the cholesterol in butter. When
olive oil and other vegetable oils are subjected to heating a lower
amount of undesirable TRANS fatty acids are formed in olive oil than
in the other oils. Use a cheaper, less flavorful pure oil for frying
and a more flavorful extra virgin olive oil on salads and as a
condiment at the table."

Olive Oil Source: California Olive Oil News©

"Olive Oil Myth:  Olive oil loses its benefits when heated

The Facts: Excessively heating olive oil will evaporate the alcohols
and esters which make up its delicate taste and fragrance. Heating
olive oil will not change its health aspects, only the flavor. Use a
cheaper olive oil which doesn't have much flavor to begin with if you
want to fry with it, add a more flavorful olive oil after cooking or
at the table.

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 trans
fat formed is miniscule and no home cook would ever experience this

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.

Olive Oil Myth:  Cooking in olive oil diminishes the nutritional value of the food.

Olive Oil Fact:   Heating food will break down its nutritional value. 
High heat such as frying is worse than moderate heat such as steaming,
which is worse than eating vegetables raw. It is not the cooking oil
per se, but the high heat of frying. I am not aware of any edible
cooking oil which of itself diminishes the nutritional value of the
food cooked in it.  Most nutritionists recommend lightly steaming
vegetables or eating them raw.  A touch of a flavorsome olive oil
added at the table will add taste and healthful anti-oxidants.  Such
is the 'Mediterranean diet' which has been shown to help prevent
coronary disease and have other health benefits."

Olive Oil Source: Cooking with Olive Oil

"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."

Olive Oil Source: Olive Oil Chemistry

"As long as you're using fats and oils sparingly in your cooking and
preparation, it would be fine to use any one of the following 'good'
oils. All of the following oils are low in saturated fats and trans
fats. Some have high concentration of monounsaturated fats such as
olive oil. Choose corn oil, safflower oil, sunflower oil, soy oil or
canola oil if you wish to fry foods as these oils have higher smoke
point. It is best not to fry with olive oil as its smoke point is only
about 190C/375F.

Good Cooking Oils: 

canola oil 
flax seed oil 
peanut oil 
olive oil 
non-hydrogenated soft margarine 
safflower oil 
sunflower oil 
corn oil 

The following 'bad' oils contain high percentage of trans fat or
saturated fats. Some, such as coconut oil, even contain more saturated
fats than animal products!

Bad Cooking Oils: 

Vegetable shortening 
Hard margarine 
Palm oil 
Palm kernel oil 
Coconut oil" 

Healthcastle: Which cooking oil is the best?

I hope this helps. If you need anything further, please request
clarification, and I'll get back to you as soon as I can.

purrsian-ga rated this answer:5 out of 5 stars
Hey, Pink!  My e-mail account must go directly to you!  Thanks for
this wonderful answer.  You are really worth your weight in good
research. ;o)

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