More efficient SFME can be attained on samples that show
higher dielectric loss (high water content), because of the strong
interaction that microwaves have with the, salt and nutrient containing,
physiological water. Thus, the matrix undergoes dramatic
swelling and subsequent tissue rupture, enabling the essential oil
to flow towards the water layer. This mechanism (I) is also based
on the ability of essential oil components to dissolve in water. In
fact, solubilisation is the limiting step and solubility becomes the
essential parameter in SFME selective extraction. Essential oils
contain organic compounds that strongly absorb microwave energy
(mechanism II). Compounds with high and low dipolar moments
can be extracted in various proportions by microwave
extraction. Organic compounds that have a high dipolar moment
will interact more vigorously with microwaves and can be extracted
more easily in contrast with aromatic compounds which
have low dipolar moments.
The purpose of the present study is to optimise the SFME recovery
of essential oil from rosemary on a laboratory scale and apply
the same conditions to a pilot scale.
Comparisons have been made between SFME (on laboratory
and pilot scales) and conventional HD as well as in terms of extraction
time, yield, chemical composition and quality of essential oil
that environmentally friendly.