Steve and others who are interested,
As this has a little
relevance to Biofuel aspects although moving off topic a bit, further to Steves
article dug out this basic article I wrote about 4 years ago when I was making
stock feed and trying to obtain maximum growth and health from animals. It is a
quick summary at the time of a 6 to 8 page article I wrote for clients.
B.r., David
REFINING of VEGETABLE OILS
SUMMARY OF STEPS, PROCESSES, AND EFFECTS
From Seed to Oil generally involves one of two processes:
a)Cold Pressing or b)Solvent Extraction
------------------------------------------------------------------------------------------------------------------------------
COLD PRESSING
1)MECHANICAL CLEANING, & COOKING
Time: = up to 2 hours
Temperature: = up to 120 degrees C ( 248 F )
2)MECHANICAL or EXPELLER PRESSING
Time: =variable
The longer the time taken, the higher the temperature & pressure, the
higher the percentage of
oil extracted (generally varies from 9 to 18% remaining
versus
Quality of oil
Temperature: = 85 to 90 degrees C ( 185 to 203 F )
3)Oil then FILTERED, & BOTTLED
SOLVENT EXTRACTION
More efficient but far less healthy
1)MECHANICAL CLEANING, &FINELY GRINDING
2)SOLVENT EXTRACTION
Immersion & soaking of ground seed in Hexane or Heptane ( petroleum )
under constant
agitation.
Temperature: = 55 to 65 degrees C (131 to 149 F )
Solvent then extracted by Evaporation at approx 150 degrees C ( 302 F )
Sometimes then mixed with mechanically pressed oil and then sold as
unrefined oil but
generally goes through several more steps.
((Up to this point there is not too much damage done with either
process but from this point
on the position quickly changes and swings very quickly in favour of
the use of unrefined cold
pressed oils
3)DEGUMMING
Removes:
Phospholipids including Lecithin ( sold as a supplement )
True Gums (type of fibre )
Protein-like compounds
Complex Carbohydrates ( Polysaccharides )
Chlorophyll
Calcium
Magnesium
Iron
Copper
Temperature: = approx 60 degrees C ( 140 F )
involves water and phosphoric acid.
4)REFINING
Oils mixed with Sodium Hydroxide ( NaOH ) ie: Caustic Soda
or a mixture of Caustic Soda and Sodium Carbonate ( Na2CO3 )
mixture then agitated and separated.
Removes:
Free Fatty Acids ( FFAs ), and further Phospholipids
Protein like substances
Minerals
Leaves pigments which are not soluble.
Temperature: = approx 75 degrees C ( 167 F )
5)BLEACHING
Using Fullers Earth and/or Acid Treated Activated Clays
Removes:
Pigments (Chlorophyll, & Beta Carotene )
Soaps formed in refining
Natural Polycyclic substances
Aromatic substances
Temperature: = 110 degrees C ( 230 F ) for 15 to 30 minutes
BUT Toxic Peroxides and Conjugated Fatty Acids formed at this point
from EFAs ( Essential
Fatty Acids ) present in the oil which can be prevented to some
extent if air is excluded from
the process
BUT Higher Temperatures must then be used which increases altered
Fatty Acids produced
by double bond shifts ( Positional Isomers ) in UFAs ( Unsaturated
Fatty Acids)
6)DEODORISING
Steam Distilation under pressure and exclusion of air
Removes:
Aromatic oils
Free Fatty Acids
Molecules imparting unpleasant odours and tastes
Temperature: = 240 to 270 degrees C ( 464 to 518 F ) for 30 to 60
minutes
Also removes:
Peroxides produced during refining and bleaching
Tocopherols ( vitamin E )
Phytosterols
Some pesticide residues
Some toxins but not all
Note: Above 150 degrees C ( 302 F ) UFAs become mutagenic ie: damage
genes
Above 160 degrees C ( 320 F ) TFAs begin to form
Above 200 degrees C ( F ) TFAs form in substantial
quantities
& Above 220 degrees C ( F ) this figure doubles again
At these high temperatures many odd and mutagenic changes take
place, none of which
happen in nature and none of which bodies are designed for
Result: Sickness, Disease, Cancer, Mutation etc.
If after reading this you would not use refined oil yourself then why feed the
same oil to your animals that you intend to eat. After all its had virtually
all of its goodness and essential nutrients stripped out of it and the only
thing really remaining is its energy value (
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