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<pre>One big difference between olive pomace oil and most of the other grades of
olive oil is the use of solvents such as hexane or isohexane to extract the
small amount of residual oil remaining after pressing. The solvent then
has to be evaporated off, leaving behind only the oil. That, at least, is
the theory. However, from own experience, I know that any solvent contains
traces of all sorts of contaminants. Even so-called analytical grade
solvents (ie very high purity) contain some contaminants. That is why it is
almost routine in many laboratories to purify solvents by distillation
before use. Crude olive pomace oil therefore may contain small amounts of
solvent impurities. The use of solvents, in addition, can result in
extraction of larger amounts of some of the components of the drupe that
are poorly extracted by normal pressing. For example, olive pomace oil
contains higher amounts of phytosterols, minor components of extra virgin
oil. If elevated temperatures are used for solvent extraction there may
also be chemical changes in some of oil components.

Olive pomace oil therefore has to be refined before it can be used for
human consumption. The chemical refining process involves a number of
steps, some reasonably drastic such as alkaline treatment, and can
introduce further chemical changes in the oil. At the same time, the
acidity is reduced and some contaminants that may have been in the solvent,
as well as pesticides, are removed.

Many of the seed oils are prepared by solvent extraction, and are also
refined. It is difficult to say whether refined olive pomace oil is better
"chemically" than refined seed oils, although you could expect big
differences in the chemical composition, particulary in the minor
components of the oils.

Alfred Poulos
Megisti Oils
www.megistioils.com
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