Extraction Technologies For Medicinal And Aromatic Plants - Unido

EXTRACTION TECHNOLOGIES FOR MEDICINAL AND AROMATIC PLANTS
a tubular heat exchanger which is heated by steam. The temperature of the
extract in the percolator is controlled by a steam solenoid valve through a
temperature indicator controller. This sort of arrangement can be incorporated
in single percolators or in a battery of percolators as needed.
The percolators that are tall cylindrical towers must be housed
in sheds of relatively great height. Tall towers are diffi cult to operate, especially
when charging material and discharging the marc from the top and bottom
manholes, which are time-consuming and labor-intensive procedures.
Tall towers have been replaced by extractors of smaller height for which the
H/D ratio is not more than 1.5.
These extractors have perforated baskets in which the material to
be extracted is charged. These perforated baskets, when loaded outside, can
be inserted into the extractor with a chain pulley block and, after the extraction,
they can be lifted out from the extractor for discharging the marc. Some extractors
have an electrical hoist for the charging the material and discharging the
marc, which makes the operation less labor-intensive, quick and effi cient.
The other type of instrument for extraction of medicinal ingredients
from plant material is the Soxhlet apparatus, which consists of an
extractor, a distillation still, a tubular condenser for the distillation still, a tubular
condenser for the recovery of solvent from the marc, a receiver for collecting
the condensate from the condenser, and a solvent storage tank. The
plant material is fed into the extractor, and solvent is added until it reaches
the siphon point of the extractor. Then, the extract is siphoned out into the
distillation still, which is heated with steam. The solvent vapors go to the
distillation condenser, get condensed and return to the extractor. The level
of the solvent in the extractor again rises to the siphon point and the extract
is siphoned out into the distillation still. In this way, fresh solvent comes in
contact with the plant material a number of times, until the plant material is
completely extracted. The fi nal extract in the distillation still, which is rich in
active principle, is concentrated and the solvent is recovered.
1.2.2.3.3 Concentration
The enriched extract from percolators or extractors, known as
miscella, is fed into a wiped fi lm evaporator where it is concentrated under
vacuum to produce a thick concentrated extract. The concentrated extract is
further fed into a vacuum chamber dryer to produce a solid mass free from
solvent. The solvent recovered from the wiped fi lm evaporator and vacuum
chamber dryer is recycled back to the percolator or extractor for the next
batch of plant material. The solid mass thus obtained is pulverized and used
directly for the desired pharmaceutical formulations or further processed for
isolation of its phytoconstituents.
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