Wow, what an excellent post! Exemplifies the reason I belong to this list.
Thank you Dr Wekell.
Jon McGraw
Seafreeze
Seattle
-----Original Message-----
From: John C. Wekell [mailto:john.c.wekell@noaa.gov]
Sent: Tuesday, June 15, 2004 11:46 AM
To: 'Strang, Mike'; 'HACCP mailing list (HACCP mailing list)'
Subject: RE: Trans Fatty Acids
In general they do not occur in nature but are the result of the
hydrogenation process. “Normal” fats that we all know and love, from fish
oil to olive oil, have their hydrogens at the double bond (--CH=CH-) in the
cis-configuration where both hydrogens are in the same plane relative to the
unsaturated double bond. In the trans configuration, one is above the double
bond and the other hydrogen is below. Classically the cis-configuration was
referred to as the “boat” form and the trans-configuration was the “chair”
form.
The trans-configuration is the least energetic state of this kind of
chemical structure and would be favored. In hydrogenation, since it is done
on a catalyst, hydrogen atoms are added at the double bond but like in all
catalysis, they also can leave. When they leave, usually the resulting
structure (if it started off in the cis-configuration) is now in the
trans-configuration. Furthermore, the unsaturation in some cases can migrate
from their original locations. Modern hydrogenation techniques can minimize
the amount of trans-fatty acid production but probably not entirely
eliminate it. For practical purposes in common edible oils, trans-fatty
acids are the result of the hydrogenation process.
In fish oils, virtually all the fatty acids are in the cis-form and most are
omega-3 fatty acids. Fish can contain fatty acids having 22 or 20 carbons
atoms and 6 to 5 double bonds—these are still omega-3 fatty acids. The
problem with these highly polyunsaturated fatty acids is that they are
extremely prone to oxidation. Great effort must be made to protect them from
atmospheric oxygen. Oxygen will react at these double bonds forming
peroxides and these in turn can break down splitting off aldehydes and other
short chain compounds. Heat, air, and trace metals, and heme can be very
strong pro-oxidants for these fatty acids.
John C. Wekell, Ph.D.
National Oceanic & Atmospheric Agency
NOAA-Fisheries
Northwest Fisheries Science Center
Environmental Conservation Division
2725 Montlake Blvd. East
Seattle, WA 98112
Phone: (206)-860-3388
FAX: (206)-860-3335
http:\\www.nwfsc.noaa.gov\hab
http:\\www.nwfsc.noaa.gov\ORHAB
This archive was generated by hypermail 2b29 : Tue Jun 15 2004 - 14:31:38 PDT