Refining olive oil
The Refined Olive Oil Process
source: www.whyoliveoil.com/refining
By definition, refined olive oil is the oil obtained from virgin olive oils by refining, acidity after
refining being 0.3%. The virgin olive oils intended for refining are ordinary olive oil and lampante
olive oil.
Refining is a process in which the undes
undesirable
irable compounds are removed, such as: free fatty acids,
pigments, gums, unpleasant flavor and odor. Generally, the refining of edible oils and fats is made in
two ways: physically and chemically (mostly used).
Physical refining is a simple process in one step using steam stripping at a temperature up to 270
degrees Celsius. Has lower cost and less chemicals are used but the final product is of lower quality.
Chemical refining has four stages:
• Degumming (removal of phospholipids; water and centrifugal sep
separation
aration are used);
• Neutralization (removal of the free fatty acids using caustic soda or sodium carbonate at 95
degrees Celsius);
• Bleaching (removal of colour and other constituents);
• Deodorization (at 180-270
270 degrees Celsius).
In the olive oil processing the same stages are followed with the specification that degumming is
replaced with settling because of small amount of phosphatides. Settling is necessary to avoid
cloudiness and sentiment in the bottle of olive oil and it also removes moisture, impurities
impuriti and some
waxes. The crude lampante oil has after this stage 10% acidity, phosphatides, metals, coloring
components and water. This will be removed by caustic neutralization when olive oil loses its bad
features. Next step, bleaching, will remove the nat
natural
ural pigments compromised by bad preservation
and responsible of unpleasant color, metals and residual soaps. Deodorization is the final treatment,
when high temperature is used.
The other half of the story is that refining process removes also the perfect attributes of olive oil.
The high temperature, stripping gas, thickness of oil layer in the deodorizer and length of the
process create changes to the quality attributes of the olive oil:
• remove all natural antioxidants
• sterols are mostly removed as well as tocopherols
• increases the content of stigmastadienes which show higher PAHs (polycyclic aromatic
hydrocarbon)
Cold pressed virgin olive oil will have unmeasurable number of stigmastadienes (maximum 0.01
mg/kg), while the refined oil can have up to 30 mg/kg. Stigmastadiene is a hydrocarbon formed as a
consequence of thermal treatments during refining process. A recent type of fraud involves
destruction of sterols during refining to mask the presence of other vegetable oils in olive oil. The
sterols are destroyed and converted to hydrocarbons. Stigmastadiene is what helps to determine
the presence of desterolized vegetable oil in virgin olive oil.
To conclude, the refining process is not only removing the defects of the lampante olive oil, but it is
also destroying the attributes of this product. The refined olive oil is still a highly monounsaturated
fat and therefore is preferable to other edible oils but cannot and must not be considered equal to
the authentic extra virgin olive oil since it lost taste, color, flavor, its antioxidants and other
nutrients. New artificial features were added to create a similar but fake product. The refined olive
oil has yellow color and mediocre taste. Actually it tastes bad. The oil might get oxidized easily and
have rancid taste. It is not advisable to consume it raw but only for frying.
Refined olive oil will be then mixed with virgin oils or will be sold directly as refined. Usually it is
labeled as olive oil, pure olive oil or light olive oil. Light indeed, not in calories (since all fats have the
same calories) but in all the rest.
Terms of marketing refined olive oils in Australia:
• Olive oil
• Olive oil (composed of refined and virgin olive oils)
• Light olive oil
• Extra light olive oil
• Pure olive oil