--- Cliff Beckwith <spinner@...> wrote:
Heat kills Omega 3. We are warned not to cook with Flaxseed
oil.
How then does it help to put Flaxseeds or Flax flour in bread?
Maybe there is an answer to this that escapes me at present.
I don't know if this will bring up answers or more questions. I
am a cynic at heart so I don't believe everything I read. The
flax council of Canada has a web site as you no doubt know.
They have a a list of PDF files on flax nutrition (aimed at
health professionals, etc.) at this address:
One file in particular caught my eye, called "Flaxseed Storage
and Baking Stability." It is at
In this file they say (in part):
Baking effects:
ALA in whole and milled flaxseed also appears to
be stable to heat equal or greater than the
temperatures involved in baking batters and doughs
such as muffins and yeast bread. Thermal stability was
shown in 1992 by the absence of significant changes in
peroxide values and fatty acid composition when both
forms of flaxseed were heated for 60 minutes at either
100C (212F) or 350C (662F). Furthermore, gas
liquid chromatography showed no signs of new trans
isomers of ALA or of cyclic fatty acid formation in
samples subjected to these degrees of heat 5 . In a
follow-up study the proportion of ALA in the fat of a
muffin mix, where 28.5% of the formula was milled
flaxseed, was virtually unchanged after baking at 178C
(350F) for 2h (45.1% ALA before:45.0% after). This
stability was observed even though oxygen
consumption of the flaxseed muffin mix was
considerably greater than that of the control muffin
mix 6 . A subsequent study confirmed the stability of
ALA in baked muffins containing the same amount of
milled flaxseed and noted that thiobarbituric acid
values, as estimates of ALA oxidation were also
unaffected by baking 9 ."
"which On reflection, the baking stability of ALA should not
be surprising considering that the internal temperature
of a muffin approaching doneness would not be
expected to exceed the gelatinization temperature of
starch. Wheat flour in the presence of sugar, or honey
in this instance, would gelatinize around 95C (203F),
much lower than the temperature of hot air in the oven
from which heat is transferred to the baking product.
A further margin of safety for the ALA-conscious
consumer is the fact that muffins are usually baked for
only 20-25 min. at 204-208C (400-425F) in contrast to
some experimental conditions 4 .
Elsewhere in the article (sorry for the poor cut and paste):
"
Flaxseed, either whole or coarsely ground, appears
stable to long-term storage at room temperature. Even
after 308 days at 22C (72F) there was essentially no
change in peroxide value as a measure of oxidation
by-products or in the percentage of ALA in fat extracted
from the stored flaxseed samples 5 . This demonstration
of oxidative stability in common storage was later
confirmed by direct measurement of oxygen
consumption. One gram samples of whole flaxseed,
milled flaxseed and extracted flax oil were held in
individual sealed glass tubes for 280 days at room
temperature with 12h alternating dark/light cycles. All
three preparations showed little change in headspace
oxygen during this time although the flax oil sample
was more variable. The fatty acid composition of all
three samples remained unchanged, suggesting that
flaxseed ALA was stable to both heat and light 6 .
These stability results with small samples have been
corroborated by studies on l kg lots of milled flaxseed
which were stored in closed packages at 23C for
128 days. The samples were examined initially and at
approximately thirty-day intervals. The packages were
triple-layer paper bags with plastic liners, much like
those used in the 60 lb. bags normally supplied to
commercial bakers. Sensory tests by a trained panel
showed no difference in the aroma intensity of water
slurries of fresh and stored samples at any of the four
storage intervals. Changes in chemical indices of
oxidation (peroxide values, free fatty acids and volatile
compounds) were negligible 7 . As further evidence of
flaxseeds storage stability, 36 consumers could not tell
the difference between the taste of yeast breads baked
with the either fresh or stored milled flaxseed included
as 11% of flour weight in the recipe 8 ."
At the end of this PDF file are 17 references, the vast majority
of which are from the mid-90's. One reference dates from 1982.
This PDF file was written in 1999; it's possible more current
information is available.
I don't pretend to be a chemist or a doctor or anything else.
It does seem to me that there IS a lot of research; and like any
research some of it has conflicting conclusions or comes from
sources that may or not be questionable. It is very possible
that there is something in flax oil that is NOT being measured
by their tests that changes when it heats it, an elusive
ingredient that hasn't been measured or perhaps an ingredient
that the researchers did not think was important that really is
and should have been measured. I don't know, I'm not a
researcher. But they have gone to great lengths to quantify the
changes that do or do not occur in various situations. This
post is but an excerpt, read the article for the whole gist and
look up their reverences.
It seems the Flax Council is at least trying to quantify their
claims (they of course have a financial interest in selling and
promoting flax consumption) and by providing articles and
references such as these they are far ahead of the majority of
web sites that make claims of flax oil curing something or
another. I have lost count of how many web sites say thing like
"flax oil will reduce your risk of heart disease" or something
like that but give no evidence, links, or research to support
their claim.
Check em out:
To get to the articles I refer to above, follow the 'nutrition'
links. To see research that the flax council supports, click on
'research'. It's nice to know who's paying for a research study
or report.
Knowledge is power!
Brian
=====
All wiyht. Rho sritched mg kegs awound?
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