OIL
The oil is made up of :
- triglycerids
- free fatty acids (1 to 10% for the unrefined oils)
- unsaponifiable matter (0.2 to 10% according to the oils)
THE
TRIGLYCERIDS
Composition
A triglycerid is made up
of 3 fatty acids fixed to a glycerol molecule.
The fatty acids are made up of a chain of carbon atoms (6 to 24),
held together by simple or double bonds. On these atoms of carbon
are fixed atoms of hydrogen.
The insaturation of oils
The level of insaturation of an oil is measured by the iodine value
(0 to 210 according to the oils).
The
saturated fatty acids
When a fatty acid does not contain any double bond,
it is called ‘saturated
fatty acid’.
The mono-unsaturated fatty acids
When a fatty acid contains a double bond, it is
called a ‘monounsaturated
fatty acid’.
The most frequent is the oleic acid (C18:1),
it can be found in every fatty body:
- It reduces total cholesterol and LDL;
- It simultaneously increases the rate of LDL
(good cholesterol). It can be found in large quantities in olive oil,
this is why this oil is so trendy.
The essential polyunsaturated
fatty acids
When a fatty acid contains several double bonds,
it is called a ‘polyunsaturated
fatty acid’.
The human body cannot synthetize the two following polyunsaturated fatty acids:
- The linoleic acid (C18:2, omega 6)
- The alpha linolenic acid (C18:3, omega 3)
This is why they are called essential fatty acids. A good daily diet should supply
them.
From them the body make up other polyunsaturated fatty acids of which namely
the EPA (C20:5) and the DHA (C22:6) from the omega 3 family.
The linoleic acid is the precursor of the Omega 6 family ;
The alpha linolenic acid is the precursor of the Omega 3 family.
Our everyday diet is too rich in Omega 6 and too poor in Omega 3, this is why
the high Omega 3 content fish oils are so valuable (namely in EPA and DHA).
Physical properties
At room temperature, the unsaturated fatty acids are liquid (oils)
and the saturated fatty acids are solid (fats).
Chemical formula
The fatty acids are identified by their number
of carbons and double bonds.
Examples :
C16 :0 : 16 carbons and 0 double bond (saturated), palmitic acid
C18 :1 : 18 carbons and 1 double bond (monounsaturated), oleic acid
C20 :5 : 20 carbons and 5 double bonds (polyunsatured), eicosapentaenoic
acid (EPA)
THE
FREE FATTY ACIDS
The free fatty acids acids are not fixed
to a molecule of glycerol and thus are not easily assimilated by
the man.
The content of an oil in free fatty acids is expressed by the oleic acidity.
Refining enables to remove these free fatty acids.
THE UNSAPONIFIABLE MATTER
Fraction that cannot be converted in soap.
According to the oils, it is made up of :
- vitamins (A, D, E in tocopherol form)
- different sterols (the analysis of these components gives a genetic
map of the oil and enables a reliable identification of the oils)
- waxes
- natural hydrocarbons (carotene, squalene,…).
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