Extraction and processing of EOs
EOs are complex mixtures of volatile compounds
extracted from plants. These low molecular mass compounds
are insoluble in water. However, the exact defi-
nition of EOs is still debated in the scientific community
[22]. The majority accept the definition of the International
Standards Organization (ISO), which limits the
extraction methods used to obtain EOs. According to
the ISO 9235.2 specifications, EO is defined as ‘A product
obtained from vegetable raw material — either by distillation
with water or steam or — from the epicarp of Citrus
fruits by a mechanical process, or — by dry distillation’
[2
,9
]. The regulation also states that steam distillation
can be conducted in the presence or absence of water in
the distillery, whereas dry distillation does not permit the
presence of water or water vapors in the still. In addition,
various possible methods of processing raw EO such as
redistillation, rectification, and aeration are highlighted.
Aromatic plants used in EO extractions are ubiquitous.
Some aromatic plants were collected from wild flora (wild
collection) growing beneficially in natural conditions.
However, most of the aromatic herbs are harvested from
systematic crops, which are cultivated under ecological
conditions.
More than 3000 types of EOs are currently known, of
which only 300 are of commercial interest [1,5].
After being synthesized in different parts of herbs, EOs
are released as an aroma through the epidermal cells of
petals, or they are accumulated and stored in different
anatomical parts of the plant, such as intracellularly
secreting cells, glandular trichomes, or secretory canals
and pockets [9
,10].
Whole aromatic herbs or parts such as leaves, flowers,
buds,seeds,fruits, roots, wood or bark are harvested during
Ava