Processing of Herbal raw material

Processing of Herbal raw material

Processing of Herbal raw material

       Primary  processing

       Secondary Processing


At the
end of this lecture, student will be able to

       Discuss the processing of herbal raw

Primary processing:

Harvested/collected medicinal plants and/or their parts undergo a series
of good practice post-harvest (and post-collection) processing procedures

Ø  Garbling

Ø  Washing

Ø  Blanching

Ø   Drying


Ø  Garbling
serves as the first step to ensure the purity and cleanness of the medicinal
plant materials.

Ø  All
extraneous and unwanted matters including dirt (e.g. soil, dust, mud,),
impurities (e.g. insects, rotten tissues), and residual non-medicinal parts
must be separated from the medicinal part(s).

Ø  The
process may involve, depending on the plant material, procedures such as
removing dirt and foreign substances, discarding damaged parts, peeling(to
separate unwanted plant parts from the medicinal plant parts such as removing
unwanted root bark from the roots or collecting stem bark from the stem)


Ø  After
sorting, the medicinal plant materials should be cleaned well to remove
remaining soil, dirt, dust, and other unwanted matters from the surface,
especially roots, rhizomes and tubers, are commonly washed with clean water,
dried soon after harvest/collection

Ø  During
the washing process, scraping and brushing may be necessary. It is generally
recommended not to soak the medicinal plant materials in water for an
unnecessarily long period of time

Ø  Change
water frequently as required


Ø  Blanching
process in which they are put into boiling water for a brief period of time
without being fully cooked

Ø  Which
improves storage life of the processed materials by gelatinizing the starch and
preventing mould/insect contamination, and facilitating further processing


Ø  Unless
used in the fresh state, the raw medicinal plant materials are to be dried
after being sorted and washed

Ø  In
general, they must be dried as soon as possible to remove as much moisture as
possible in order to ensure good keeping qualities and to reduce damage from
mould and other microbial infestation

Ø  Drying
will also avoid tissue deterioration and phytochemical alteration caused by the
actions of enzymes and microbial organisms; and will also facilitate grinding
and milling


Ø  Most
medicinal plant materials can be dried in open-air under direct sunshine,
provided the climate is suitable for such a practice

Ø  The
duration of the drying process depends largely on the physical structure of the
medicinal plant material and the weather condition

Ø  In
the case of natural drying in the open air, medicinal plant materials should be
spread out in thin layers on drying frames and kept away from possible
contaminations such as vehicle exhaust, heavy dusts, and rain, as well as
protected from insects, rodents, birds and other pests

Shade Drying:

Ø  Some
medicinal plant materials can be dried in the shade with or without artificial
air flow to avoid direct exposure to strong sunlight

Ø  Drying
process is slow, but it is preferred to maintain (or minimize loss of) colour
of leaves and flowers

Ø   Low temperatures will also preserve most of
the volatile and aromatic components from being evaporated

Artificial Drying:

Ø  Drying
by artificial heat is more rapid than open-air drying and is often necessary on
rainy days or in regions where the humidity is high.

Ø  For
artificial-heat drying, the temperature, humidity and other conditions should
be governed by the physical nature of the drug and the physical/chemical
properties of its active ingredients.

Ø  Over-heating
may lead to an excessive loss of the volatile components and/or decomposition
of chemical ingredients. As much as possible, the temperature should be kept
below 60°C.

Tray dryer

dryer/cabinet or compartment dryer

hot air oven

spread in thin layer in trays

of trays depends on the size of the oven

air of desired temperature is circulated

material is taken out, cooled and pulverized

Secondary Processing

Cutting, sectioning, and communition: When thoroughly
dried, the herbal materials are processed by cutting and sectioning into
convenient sizes and shapes for storage,

Ø  Where
applicable, the herbal materials should be cut or sectioned into specific
shapes or forms, or comminuted/pulverized into powder form according to common
practice found in herbal medicines

Ageing/Sweating:  The
aging process refers to storing the herbal materials for a period of time after
being harvested or collected from the field prior to use.

Ø  It
is generally done under the sun or in the shade for up to a year, depending on
the specific herbal material. During the process of aging, excessive water is
evaporated and enzymatic reactions may occur to alter the chemical composition
of the herbal material.

Ø  For
example, cascara sagrada bark should be aged for at least one year prior to use

Ø  A
similar process known as sweating involves keeping the herbal materials at a
temperature of 45-65°C with high humidity for an extended period of time, from
one week to a couple of months, depending on the plant species

Baking/Roasting: It is a dry-heating procedure using
indirect, diffused heat, where the herbal materials are put in a heating
device, often embedded in bran or magnesium silicate (talc) powder to ensure
even heating on the entire surface at an elevated temperature for a period of

Ø  Some
herbal materials are wrapped in moistened papers during the roasting process.
The exact temperature used and duration of baking/roasting vary from one herbal
material to another.

Ø  Some
are baked or roasted until the surface colour turns yellowish brown; some may
be further heated until charred.


Ø  Fumigation
by sulphur dioxide has been employed in post-harvest handling of some medicinal
herbs for the purpose of preserving colour, improving fresh-looking appearance,
bleaching, preventing the growth of insect and overcoming decays caused by


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