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Refining and Processing Oils
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A different point of view from an engineer in the industry of which I am not... 4 Jun 00
Mark,
I am a chemical engineer in the oilseed industry. Every once in a while I read
articles on the net to see if there are any new ideas or techniques around.
I was reading your description on trans fatty acids. I just wanted to let
you know that some of the information in the EFA description is not
altogether correct. For instance, the description on cis versus trans fatty
acids. It is not so important that the Hydrogen atoms move. It is that the
double bond is momentarily weakened and the carbon chain flips to where the
hydrogen atom was. You see, the molecule looks much different three
dimensionally. Correctly stated that most oilseeds have a higher
concentration of the cis-configuration when brought in from the field.
However, in order to remove many of the harmful, bad tasting, and easily
oxidized material from the oil (aldehydes, ketones, hydro-peroxides,
free-fatty acids (which easily oxidize and smoke, discolor in a
skillet/fryer), sterols, tocopherols (a natural antioxidant which will also
discolor in a skillet at naturally occurring high levels), and other
hydrocarbons), the oil must be deodorized at the elevated temperatures. This
is because they will not boil off until they reach the high temperatures.
Yes, the cis-to-trans conversion can occur at these temperatures. However,
the conversion happens more readily during hydrogenation.
People like shortening because it is more stable and has special
characteristics that help bread bake a certain way, give a good consistency
to products, and extend the shelf life. Unfortunately, hydrogenation also
increases the degree of saturation - which is worse than converting from cis to
trans (no matter what anyone tells you, saturated fat is worse than a trans
containing lipid). A saturated fat has a much higher internal energy than a
trans unsaturated fat with the same basic backbone. You see, although nature
dictates that oilseeds contain more cis fatty acid chains in the field,
nature also dictates that molecules always do seek the most stable energy
level. And the most stable energy level is the one with the highest internal
energy. In laymen's terms, this means they are harder to break down, because
more calories have to be supplied in order to do so. It's in the books.
Yes, the cis configuration is better and breaks down more readily. However,
no one has been able to completely eliminate the conversion of cis-to-trans.
It is impossible to keep your cooking oil prices anywhere near affordable and
supply a 100% cis fatty acid oil. Whoever comes up with a solution will most
likely be a very wealthy person.
Also, the statement about some of the catalyst staying in the oil. This
is not mysterious by any means. The catalyst producers put a saturated
(stearic acid oil ) carrier around the catalyst to give it a more easily
manageable shape and consistency. The only thing that stays in there after
hydrogenation is pure stearine, which is already in the oil anyway!
Let's not forget what we learned 30 years ago. Saturated fats are very
harmful. If they were less harmful than trans unsaturated fats, wouldn't you
think that we would have discovered them after trans? An effective plan to increase cis-fatty
acids in cooking oils should be aimed at end users such as restaurants, since
they are the ones who put the specifications on the industry. Meanwhile, my
suggestion to you and all health conscious people would be to purchase a
once-refined peanut oil for your cooking and be done with it. I am also a
cook and a health enthusiast, and this is what I use. NDCHEG@aol.com
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Introduction: Oils fresh out of
the seed are mostly nutritious and healthy. The seeds rich in Essential Fatty
Acids (EFAs) contain many valuable side components. By and large, they contain
all the essential vitamins and minerals needed for their own assimilation.
Many of these components are rich in antioxidants. As unprotected EFAs
go rancid quickly, the last thing the oil manufacturers want is to have us
purchase their oil in the grocery store, just to find that it has gone rancid.
To prevent this, they remove and alter them. And what a price we pay!
By the time the oils we eat have been through the refinement process, a radical
change has taken place.
- Extraction: The oil is extracted
from the seed by mechanical extraction through a screw press.
This removes all but 9 to 18% of the oil in the `seed cake' depending
on how good the press is. Today's standard screw presses do not protect
the oil from light or oxygen. Because of this, the oil starts to become
rancid from the very beginning. This oil is sometimes sold as `unrefined
oil' in health food stores even though it has already been damaged. To
get the other 9 to 18% oil from the seed cake, companies often use a petroleum
solvent. After the oil/solvent mixture is mechanically extracted from the
crushed seed, the solvent is removed from the oil at a temperature of about
300 degrees F. (150 C).
- Degumming: The degumming process removes
phospholipids, including the lecithin. It also removes iron, copper, calcium,
and magnesium.
- Refining: The oil is mixed with the
base sodium hydroxide (A base is the opposite of an acid. Sodium hydroxide
is what gives 'Drano' its kick). It mixes with the free fatty acids forming
soap. Refining the oil also removes more minerals and
phospholipids.
- Bleaching: Bleaching removes the
beta-carotene. Of note, the temperature at which this happens is 230 degrees,
(110 C) the threshold at which fatty acids begin to become altered.
- Deodorizing: Deodorizing removes the
aromatic oils, and any remaining free fatty acids. This takes place at 464-518
degrees F (240-270 C) for 30-60 minutes.
The end result: By the time the
process is complete, the oil is odorless, tasteless, and has no natural vitamins
or minerals. Not only is everything taken out, but the oil that remains has
been severely damaged by the high temperatures of the refinement process.
It really is `white oil.' (Sometimes, at the end of the refinement process,
the manufacturers add artificial antioxidants to ensure any remaining EFAs
won't go rancid! The natural is taken out, then artificial substances put
in.) Be aware that above 300 degrees F (150 C), unsaturated fatty acids become
mutagenic, IE, they become dangerous to our genes. Above 320 degrees F (160C)
trans- fatty acids begin to form. Above 392 degrees F (200 C) trans- fatty
acids form in substantial quantities. Remember the deodorizing temperature
is far above this, at 464-518 degrees F (240-270 C). But I've got the `cart
before the horse' again. Lets talk about trans- fatty acids.
Introduction:
Shown above is the essential fatty acid, Alpha-Linolenic Acid. Remember,
at the double bonds the missing hydrogen atoms all come from one side. This
is called the cis- configuration, and shows the EFA in its natural
state. When unsaturated fatty acids are overheated, the hydrogen atoms tend
to jump around. The picture below shows LNA in its trans-
configuration.
Shifting of atoms: The
gray H's in the above illustration show where the hydrogen atoms were before
heating. The red H's show the spots they moved into. Notice that they
flipped sides. Even though the same number of carbon and hydrogen atoms are
in the molecule, this is not at all the same fatty acid. For example, because
there is now a balanced number of hydrogen on each side of the molecule,
it no longer bends, but is straight like the saturated fatty acid. Its melting
point has also dramatically raised. And in our bodies it acts more like a
saturated fatty acid than an unsaturated oil. The bottom line is the oil
manufacturers are pleased to tell us their oil is `polyunsaturated,' knowing
we have enough smarts to understand this means `good oil.' But they don't
bother to tell us how much of it is in the trans- configuration. Our body
knows how to deal with trans- fatty acids, to a point. It burns them up to
form energy. After the point of tolerance is reached, however, it can confuse
them for EFAs. When it sees a need for an EFA, it reaches out and grabs an
altered fatty acid and plugs it in. Only it doesn't work! Many researchers
believe this to be one of the root causes of some of our greatest health
challenges of the modern age: cancer and heart disease.
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Al Durtschi, E-mail: mark@waltonfeed.com
Home Page: http://waltonfeed.com/
Much of the information for the EFA pages was taken from Fats that
Heal Fats that Kill by Udo Erasmus, Published by Alive Books, Burnaby,
BC, Canada 1-800-661-0303
All contents copyright (C) 1995, Al Durtschi. All rights reserved.
Revised: 19 Jun 00