Agriculture Reference
In-Depth Information
PE (pectinmethyl esterase at a dose of
when they left hemp to rot in waterways or
retting baths for 3 weeks or more. 4
2. Straw colour. The longer retting takes, the
more the straw, and therefore the fibre, goes
brown, or even black, before it eventually
becomes completely rotten.
3. The more the fibre is grey or black, the
more the hurds will be grey or black.
4. Loss of material. As soon as the bacteria
attack, they start to consume plant material.
This is particularly pronounced if the straw is
manipulated, because when the stems are
broken, the hurds are released. In the past,
the hemp farmer would allow the hurds to rot
away completely until they were washed
away. Hurds that were collected during deco-
rtication were used to stoke the fires that
dried the hemp before it was processed fur-
ther. Today, the manufacturer seeks to make
use of all parts of the plant, including the
hurds. It is therefore not in the manufactur-
er's interest to lose this part. Hence, the
manufacturer will therefore seek a weak to
moderate degree of retting in order to mini-
mize this loss.
135,780 PE/g).
The preparations tested were essentially pec-
tinolytic and hemicellulolytic enzymes that
acted by dissolving the cell walls to release the
fibres. These enzymes are produced by micro-
organisms during fermentation, including a
'bacillus' species and a culture of Aspergillus
niger .
Different varieties of enzymes with various
capacities for breaking down pectin were
tested. The filtrates of these stabilized, and
concentrated enzyme cultures were then dis-
solved in an aqueous solution at a pH of 4.0
for the pectinases PE and PGU, and at a pH of
8.0 for BioPrep 3000 L, and then placed in
contact with the fibres.
The samples obtained were shaken
mechanically for between 0.5 and 2 h at 40°C
for the pectinases PE and PGU and at 60°C
for the BioPrep 3000 L. They were then neu-
tralized and rinsed for 2 min in cold water.
In principle, this procedure does not
appear overly complex. How complex is it in
practice?
The authors concluded their paper indi-
cating that the research conducted on the
enzymatic separation of fibres demonstrated
their viable potential as a means of producing
fine fibres with high-tension resistance. The
BioPrep 3000 L was described as the best per-
forming enzyme. They qualify their findings by
adding that these experiments need to be
repeated in an industrial setting.
At the time of writing, despite numer-
ous experiments being conducted in China,
Italy and Germany, a procedure suitable for
industrial use does not appear to have been
found.
Sought-after fibre qualities 5
The analysis of fibre quality is based on three
criteria: purity, colour and fibre position.
PURITY . The degree of purity (or of refinement)
that is sought is expressed as a proportion of
the hurds. 9 For industrial use (for technical
fibres), the purity sought has a level of hurds/
fibre
2%. For paper production, the level can
be as high as 35%. For the production of yarns
and textile threads, string or rope, the level
must be close to 0%.
COLOUR . Although today this is not a deciding
criterion of choice, the preferred sought-after
colour is white or blonde, or at the very least, a
light colour.
NB The issue of colour will be revisited
when it comes to hurds, for the users of hurds,
whether it be as animal bedding, in hemp
cement or plaster, all require white hurds.
Results of retting
There are four principal results of retting:
1. Ease of fibre extraction. The more the straw
is retted, that is to say the longer and more
pronounced the enzymatic attack, the easier
will be the fibre extraction. Thus, if we are
looking to make the work easier, it makes
sense to allow retting to take longer. This was
what the ancient hemp farmers were doing
FIBRE POSITION . The main users of hemp fibre
(industry and paper manufacturers) do not
 
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