Composition of EOs
Steam distillation is the most commonly used
method for producing EOs on a commercial basis.
Extraction by means of liquid carbon dioxide under
low temperature and high pressure produces a more
natural organoleptic profile but is much more expen-
sive (Moyler, 1998). The difference in organoleptic
profile indicates a difference in the composition of oils
obtained by solvent extraction as opposed to distilla-
tion and this may also influence antimicrobial prop-
erties. This would appear to be confirmed by the fact
that herb EOs extracted by hexane have been shown
to exhibit greater antimicrobial activity than the
corresponding steam distilled EOs (Packiyasothy
and Kyle, 2002). EOs are volatile and therefore need
to be stored in airtight containers in the dark in order
to prevent compositional changes.