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Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5260

RETTING PROCESS OF SOME BAST PLANT FIBRES AND ITS
EFFECT ON FIBRE QUALITY: A REVIEW

Paridah Md. Tahir,
a
Amel B. Ahmed,
a
Syeed O. A. SaifulAzry,
a
and Zakiah Ahmed
b


Retting is the main challenge faced during the processing of bast plants
for the production of long fibre. The traditional methods for separating the
long bast fibres are by dew and water retting. Both methods require 14
to 28 days to degrade the pectic materials, hemicellulose, and lignin.
Even though the fibres produced from water retting can be of high
quality, the long duration and polluted water have made this method less
attractive. A number of other alternative methods such as mechanical
decortication, chemical, heat, and enzymatic treatments have been
reported for this purpose with mixed findings. This paper reviews
different types of retting processes used for bast plants such as hemp,
jute, flax, and kenaf, with an emphasis on kenaf. Amongst the bast fibre
crops, kenaf apparently has some advantages such as lower cost of
production, higher fibre yields, and greater flexibility as an agricultural
resource, over the other bast fibres. The fibres produced from kenaf
using chemical retting processes are much cleaner but low in tensile
strength. Enzymatic retting has apparent advantages over other retting
processes by having significantly shorter retting time and acceptable
quality fibres, but it is quite expensive.

Keywords: Kenaf; Bast long fibres; Retting; Fibre characteristics; Pectic materials; Enzyme

Contact information: a: Laboratory Biocomposite Technology, Institute of Tropical Forestry and Forest
Products, Unversiti Putra Malaysia, 43400 UPM Serdang, Selangor Darul Ehsan Malaysia; b: Faculty of
Civil Engineering, Unversiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor, Malaysia;
* Corresponding author: parida_introb@yahoo.com; parida@putra.upm.edu.my


INTRODUCTION

Plant fibres such as sisal, ramie, bamboo, kapok, pineapple, coir, hemp, jute, flax,
and kenaf are generally classified by the part of the plant from which they are obtained
such as leaf, seed, fruit, stem, and bast. As its name implies, bast fibres are obtained
from the outer layer, i.e. the inner bark or phloem, of bast surrounding the plant stem.
The fibres are usually very long (as long as the stem) and are relatively strong. For this
reason, the bast fibre is considered to be the most important fraction of any bast plant.
Since all plant fibers are made up of mainly cellulose, they are categorised as natural
cellulosic fibers, which may consist of one plant cell or an aggregate of cells cemented
together by non-cellulose materials. Thus, a cellulosic fiber can be either unicellular like
wood and cotton, or multicellular like jute, hemp, flax, and kenaf (Sur 2005). J ute, for
example, has 5 to 15 cells, i.e. the ultimate cell, which may be reduced upon storing or
processing. Because of this characteristic, fibers that are separated from bast plants are
often referred to as crude fiber (aggregates of single fibers bound together), which are
usually much coarser and much longer, whilst those reported in many studies are defined

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Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5261
based on scanning electron micrographs of microfibrils or single-strand fiber. Hence the
reported average fiber lengths and widths reported are much smaller, e.g., respectively
2.5 mm and 18 m for jute (Sur 2008), versus 2.3 mm and 16.1 m for kenaf (Paridah et
al. 2009). The terminology is sometimes interchangeable, thus readers may have to make
their own inferences based on the context of the discussion.
Bast fibres are produced and used to manufacture a wide range of traditional and
novel products; these include textiles, ropes and nets, carpets and mats, brushes, and
mattresses, in addition to paper and board materials. They can be used in many ways, for
instance, in the form of fine powder as in sawdust, short fibres as in random and non-
woven mat, or even long fibres as in woven mat, for making various kinds of
biocomposite products. Some composites made from natural fibres have useable
structural properties at relatively low cost (Mohanty et al. 2001). Advantages of bast
fibres over the traditional reinforcing fibres such as glass and carbon include low cost,
low density, high toughness, acceptable specific strength properties, improved energy
recovery, carbon dioxide sequestration, and biodegradability. With the increasing
consciousness of preserving the environment and the need to recycle, there has been
renewed interest in composite sectors using natural fibres as partial replacement for
synthetic carbon, glass, or aramid fibres. Long fibres offer greater flexibility for
enhancement processes, particularly in the woven and pultrusion composite industries
(Paridah and Khalina 2009). The long fibres are transformed into threads or yarns that are
used to join, connect, or attach to each other. According to Sur (2005) any textile fibre
should be made up of long-chain molecules so as to ensure continuity and strength along
the length of the fibre axis. The homogeneity of this long fibre depends very much on the
technique of producing the fibre bundles, which is known as the retting or degumming
process.


COMMON BAST FIBRES

Hemp (Cannabis sativa L.) is the earliest developed source of plant bast fibre, and
it has gained considerable interest, since it produces a strong and durable fibre
(Kymalainen 2004). Hemp prefers a mild climate, humid atmosphere, and a rainfall of at
least 625 to 750 mm (25 to 30 inches) per year. Hemp requires a good soil moisture for
seed germination, and for young plants to grow until about a month old. The world hemp
fibre market is dominated by low cost producers such as China, South Korea, and the
former Soviet Union, which together produce about 70% of the worlds supply. It was
restricted as a narcotic drug in the US in 1948; thus the cultivation of this plant has since
been limited. Nevertheless, many traditional growing countries still continue to produce
textile grade fibre from hemp. Studies to develop composite materials from hemp fibres
for building industry are also being carried out (Thygesen 2005).
J ute (Corchorus capsularis and Corchorus olitorius) is the most important bast
fibre in Bangladesh and India. In hot and humid climate jute plants can be harvested
within 4 to 6 months. J ute is traditionally used as textile fibres for fabrics, particularly
for making jeans and other heavy-duty types of fabrics. As a textile fibre, jute produces
poorer quality fabrics compared to cotton and silk. To improve the quality, many jute

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Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5262
yarn producers blend their products with either cotton or silk for making apparels.
However, the major breakthrough came when the automobile, pulp and paper, and
furniture industries started to use jute for the production of non-woven and woven
composite materials. Nowadays, more jute manufacturers are shifting their interests
towards biocomposites and pulp and paper products. Amongst the bast fibre plants, jute
has become the most produced and traded in the world markets.
Flax (Linum usitatissimum) production goes back to ancient history. It can be
grown and harvested within three months under reasonable moisture and relatively cool
temperatures (Oplinger et al. 1989). Flax has also been considered as a source of linen,
providing high-quality fibres for textiles for thousands of years (Lamb and Denning
2004). Longer fibers are used for spinning into yarn and making textiles, a fabric type
that is also known as linen. Shorter flax fibers are either spun into yarns, often mixed
with cotton, or used in many other novel applications including packaging materials,
reinforcements for plastics and concrete, asbestos replacement, panel boards, lining
materials for vehicles, and alternatives for fiberglass as an insulation material. One
advantage of flax fiber is its ability to absorb up to 12% of its own weight in water, and
its strength increases by 20% when wet. It also dries quickly, and it is anti-static. For
some applications it is a suitable substitute for man-made synthetic fibers such as heavier
fiberglass. The fibers are twice as strong as those of cotton and five times as strong as
those of wool (Garstang et al. 2005).
Another equally popular plant fibre is kenaf (Hibiscus cannabinus L.), which
sometimes is used interchangeably as mesta (Hibiscus sabdarifa). Both types grow well
in tropical and sub-tropical areas. The characteristics of kenaf fibres (both bast and core)
are similar to those of wood, while hemp, flax, and jute fibres are substantially different.
According to research results (Wood 2000; Rymsza 2000; Kozlowski 2000), kenaf yields
are greater than those of hemp, flax, and jute, thus providing a more cost-effective raw
material. The dry fibre yield was reported to be between 5 and 6% of the fresh stems, and
this equals 18 to 22% of the dry plant. In the U.S., dry yields of 1 to 2 ton/ha have been
reported, but yields of 3 to 4 ton/ha can be reached under ideal conditions (Dempsey
1975). Paridah and Khalina (2009) reported that under a Malaysian climate, yields of
kenaf vary from 2 ton/ha to 25 ton/ha, depending on among others, soil type, month
planted, variety, and planting density.
Kenaf has a long history of cultivation for its fibre in the U.S.A, Bangladesh,
India, Thailand, Australia, Indonesia, and to a small extent in Southeast Europe, parts of
Africa, and Brazil, where it is cultivated throughout the year. Similarly with other bast
fibres, kenaf comprises two distinct fibres: the bast (30% of the total dry weight of the
stalk) and the core (70%) fibres (Sanadi et al. 1997). In addition, the whole parts of kenaf
stem can be used to make composites or other products. The core part resembles low-
density wood, having light straw colour and density of about 0.1 g/cm
3
.
Kenaf and jute are among the least expensive, most versatile textile fibres and
provide reliable employment in many rural areas (Rome 1998). In many developing
countries such as India, Thailand, and Indonesia the development of kenaf industry may
be the key to future advancement of rural areas, provided that kenaf can be tailor-made
for specific higher value products such as technical textile, security paper, winery notes,
etc. Such applications rely very much on the retting method, a process of separating the

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Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5263
bast fibres from the core and converting these fibres into individual fibres. Retting
degrades the pectin-rich bast and lignin in the middle lamella that is connected to the
adjacent fibre cells, releasing individual bast fibres (Sur 2005; Zhang et al. 2005). The
long period of natural degradation, which normally ranges from 14 to 28 days, can be
considered as the dominant problem in the production of long fibre. Water retting, the
conventional method for long fibre production, was reported to generate much water
pollution (Lu et al. 1999). In rural areas of China, Bangladesh, and India, a paddy field
method of retting has been practiced in a fixed and small area, but the resulting fibre is
very much degraded (He and Zhao 1990). Other types of retting have been extensively
studied, such as low cost pond (Anon 2009), mechanical decortication, and water and
chemical retting (Paridah and Khalina 2009; Kawahara et al. 2005; Goodman et al. 2002).
Kenaf cultivation has declined significantly since 1990 (FAO 2008) due to land
inavailability, competition with other food crops and slow technological advancement in
mechanization. Nevertheless from the reports of Food and Agriculture Organization
(FAO) (Anon 2008) and the International J ute Study Group (IJ SG) (Anon 2009) the
demand for kenaf has never been diminishing, and in fact it is still growing. Such
increment is due to the global awareness and trend of using green material, and kenaf
offers many advantages over other bast plants, particularly for the Asian region.
This paper reviews the production, anatomy, retting processes, and the effects of
retting method on fibre qualities of four major bast fibre crops, namely hemp, jute, flax,
and kenaf. Since kenaf has been recently declared as Malaysias seventh commodity, this
review mainly focuses on the use of kenaf fibres as compared to hemp, jute, and flax.

Annual Production of Bast Plant Fibres
Detailed global supply/demand and price analyses for hemp, jute, flax, and kenaf
are not available widely. The following statistics were taken from various sources, hence
may have some discrepancies in the basis of calculations. Nevertheless, for comparison
purposes the values are quoted as they appeared in the respective sources. Tables 1, 2,
and 3 show the current world leading producers of jute, hemp and flax, and kenaf,
respectively. J ute continues to dominate the natural fiber market with a continuous stable
supply at 3,225,000 tonne, whilst hemp and flax together are close to 300,000 tonne, and
kenaf is at an average of 400,000 tonne annually.

Table 1. Top World J ute Producers in 2008 by Country
Country Production (x 10
3
tonnes)
India 2,1401
Bangladesh 8001
People's Republic of China 992
Cte d'Ivoire 401
Thailand 311
Myanmar 301
Brazil 26.712
Uzbekistan 201
Nepal 16.782
Vietnam 111
World 3,225.49
Source: Food And Agricultural Organization of United Nations: Economic and
Social Department: The Statistical Division, 2008

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Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5264
Table 2. Top World Flax and Hemp Producers in 2005
Country Production (x 10
3
tonnes)
Flax Hemp
Long Flax fiber
[tonnes]
Short Flax
fiber [tonnes]
Total
Belgium 19 .03 11.89 30.92 -
Czech Rep 2 .93 3.55 6.48 . -
Germany 0.11 0.12 0.23 2.36
Spain - - - 1.7
France 105 75 180 14
Italy - 0.13 0.13 0.42
Lithuania 0.32 0.75 1.07 -
Latvia 2.54 3.80 6.34 -
Hungary - - - 0.94
The Netherlands 4.52 3.33 7.85 0.08
Austria 82 0.13 82.13 0.44
Poland 0.15 0.12 0.27 0.14
Finland - 0.10 0.10 0.008
UK - 0.12 0.12 1.58
People's Republic of China 25 - 25 43
Total 340.64 64.67
Source: Food And Agricultural Organization of United Nations: Economic And Social Department:
The Statistical Division, 2008. Note: Values were rounded to two decimals.


Table 3. Top World Kenaf Producers
Country Production (x 10
3
tonnes)
2004 2005 2006 2007 2008
India 198.00 203.20 202.14 198.70 156.40
People's Republic of China 125.90 136.00 155.00 165.00 86.92
Thailand 29.60 29.50 41.00 57.00 35.66
Vietnam 11.30 14.60 20.50 21.00 14.20
Brazil 7.30 7.20 10.20 10.90 12.65
Cuba 10.00 10.00 10.00 10.00 10.00
Indonesia 7.00 7.00 6.82 7.00 7.00
Myanmar 1.63 3.73 9.45 11.27 5.26
Cambodia 0.20 0.20 0.50 0.50 0.65
World 390.93 411.43 481.37 481.07 328.74
Source: Food And Agricultural Organization of United Nations: Economic And Social Department:
The Statistical Division, 2008. Note: Values were rounded to two decimals.

Table 4 shows the world annual production and prices for hemp, jute, flax, and
kenaf. Both hemp and flax have been dominated by the European countries, whilst jute
and kenaf by the Asian. The prices of bast fibres from these stems range from USD$
0.60 to 0.90 per kilogram, with jute maintaining reasonably high prices. These are the
prices officially quoted by various reports up to the preparation of this manuscript. As
indicated in Table 4, among the four bast fibres, kenaf seems to be more economically
favorable, producing reasonably high yield with a good selling price. Kenaf prices have
escalated between five to eight times as a result of new demands by composite industries

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Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5265
that include building, automotive, defense, and aerospace in their efforts to combat the
current environmental issues, and in meeting the government policy. This trend can be
seen in the Malaysian kenaf market, as shown in Table 5. The Malaysia climate with its
abundant sunshine, together with availability of rainfall throughout the year offers a
suitable environment for kenaf. In such a climate, kenaf is able to grow all year round and
can be harvested twice a year. Other Asian countries that fall under the same category
are Thailand, Indonesia, Myanmar, and Vietnam. Between 1990 and 2002 Thailand used
to be the major producer and consumer of kenaf (Anon 2003); however this scenario has
changed due to competition with other crops as well as environmental issues due to water
retting.

Table 4. Annual Production and Prices of Hemp, J ute, Flax and Kenaf
Fibre
type
Botanical
name
Family Main sources Stem
production
(10
3
Tonnes)
per hectare
Prices
($/kg) of dry
bast fiber

Refer-
ences
Hemp Cannabis
sativa L.
Cannabaceae Germany, UK, France
and possibly Romania
214

0.7-0.8 1,2,5,6
J ute Corchorus
capsularis,
Corchorus
olitorius

Tiliaceae Bangaladesh, India 2850

0.8-0.9 5,6,7
Flax Linum
usitatis-
simum
Linaceae France, Spain,
Belgium, Lithuania,UK
830 0.6-0.8 1,2,3,
4,5,6
Kenaf Hibiscus
cannabinus
Malvaceae Bangaladesh, China 970 0.7-0.8 1,2,5,6
1 Rebson et al. 1993; 2 Rwell and Han 2000; 3 Semder and Liljedahl 1996; 4 Karus and Kaup
2002;
5
Mwaikambo et al. 1999; 6 llison and McNaught 2000, 7 Riccio and Orchard 1999.

Table 5. Selling Price
1
of Kenaf Stem, Short Fiber and Core in Malaysia

Raw material USD/tonne
2007 2008 2009 2010
Stem 91 91 152 152
Short fiber (70mm-
150mm)
n/a 525 525 525
Core n/a 46 91 91
1
One US Dollar is equivalent to RM3.06 (as of October 2010)
Source: Kenaf Fibre Industries, 2010


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Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5266
Anatomical Structures of Bast Fibres
Generally, bast fibre bundles are composed of elongated thick-walled ultimate
cells that are joined together both end-to-end and side-by-side, forming aggregates of
fibre bundles along the height of the plant stem. During the growing period of the stem, a
circumferential layer of primary fibres are developed from the protophloem, but, as
vertical growth ceases in the lower parts, the secondary phloem fibres (where the bast
fibres can be obtained) are developed as a result of cambial activity. Figure 1 shows
stem and cell structure of hemp, jute, flax and kenaf. Unlike cotton which is unicellular,


Type of plant
Hemp Jute Flax Kenaf




Stem












cells
Cross-section of
hemp bast fibers.
(6)


J ute stem
(combined
transverse section
and longitudinal
section).
(5)

Flax stem in
transverse section.
(4)

Bark (lower part)
and core (upper
part) in transverse
section.
(3)


Fig. 1. Stems and cell structure in, hemp, jute, flax, and kenaf fiber
1
(Goodman et al. 2002),
2
(Voulgaridis, et al. 2000),
3
(Oliver and J oynt 1999),

4
www.sbs.utexas.edu/, mausethweblab/, webchap5scler/ 5.1-4.htm,

5
Rowell and Stout 1998),
6
(Tavisto et al. 2002).

these fibres have multicellular type cells. The cross section of jute cell is polygonal with
slightly rounded corners and a medium-sized lumen. Retted jute fibres normally contain
15 to 30 fibre cells (Sur 2005) whilst the number of fibre bundles in the stem of flax
ranges from 15 to 40. Each bundle contains between 12 and 40 ultimate fibres. The
ultimate fibres consist of pointed cells with very thick walls and very small lumens.
Goodman et al. (2002) investigated each flax fibre bundle using light microscopy and
revealed that flax fibres originate from primary phloem tissues which are located between
the outer cortical tissue and the secondary phloem tissues. Each fibre contains 30 to 40
ultimate fibres. In another study, Oliver and J oynt (1999) clearly observed the cross-

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Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5267
section of hemp stem and found that its bast fibres are composed of primary bast
fibres, which are long and low in lignin, and secondary bast fibres, which are
intermediate in length and higher in lignin.
Depending on the location in the stem, kenaf contains three types of fibre: bast,
core, and pith. The fibres from bast are long and have thick cell walls, whilst those of
core fibre are thinner with much shorter fibre length (Paridah et al. 2008). The core
fibres appear as wedge-shaped bundles of cells intermingled with parenchyma cells and
other soft tissue. The pith consists exclusively of parenchymatous cells, which are not
typically prismatic but polygonal in shape. In mature plants, kenaf can reach a height of
2.5 to 3.5 m (Rowell and Stout 1998). Zhang 2003 reported that the kenaf fibers are
shorter at the bottom of the stalk and longer at the top. The increase in length from the
bottom to the top was found not to be gradual, but S-shaped (Rowell and Han 1999). It
was reported that the fibre length increases during the early part of plant growth, and
decreases again as the plants mature (Chen et al. 1995). Kenaf single fibers are only
about 1 to 7 mm long and about 10 to 30 microns wide, thus too short for textile
processing (Calamari 1997). Compared with cotton fiber, these fibres are coarse, brittle,
and not uniform, which makes them difficult to be processed using conventional textile or
nonwoven fabric equipment. Table 6 compares the morphology of natural cellulosic
fibres against other types of bast plants.

Table 6. Morphology of Natural Cellulosic Fibres
Type of fibre Cell type Cross-sectional shape of ultimate cell
J ute
Mesta
Kenaf

Multicellular
Polygonal with slightly rounded corners and medium-
sized lumen
Ramie

Multicellular Elongated ellipse with collapsed elongated lumen
Flax Multicellular
Appreciable roundness in the corners and medium
size lumen
Hemp
Pineapple

Multicellular Oval cross-section with collapsed small size lumen
Sisal Multicellular
Polygonal with sharp corners and medium to large
size lumen
Coir Multicellular Polygonal with rounded corners and large size lumen
Cotton Unicellular
Peanut-shaped cross-section of each fibre with
elongated collapsed lumen
Source: Sur (2005)



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Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5268
RETTING OF PLANT FIBRES

Most bast fibres are cemented to the adjacent cells inside the stem with pectin (a
form of carbohydrate), which can be extracted by retting processes. Retting is sometimes
termed degumming. It is a chemical process for removing non-cellulosic material
attached to fibres to release individual fibres. After harvesting, the stems are usually kept
either in the field or under water for 2 to 3 weeks, during which the pectinous substances
that bind the fibre with other plant tissues are softened and degraded by micro-organisms.
A quality of fibre is largely determined by the retting condition and duration. Table 7
compares five types of retting processes, namely, dew, water, enzymatic, mechanical, and
chemical retting, which are normally applied to hemp, jute, flax, and kenaf. Apparently,
there is no single method that can give optimum results in terms of retting period, fibre
strength, environmental pollution, and cost. Dew retting largely relies on indigenous soil
fungi to colonise the stem/bast and to degrade pectin and hemicellulose (particularly the
arabinose) by releasing polygalacturunase (PGase) and xylanase (Brown et al. 1986).
The resulting fibres are often coarse and of variable quality. Conversely, water retting is
performed in an aqueous environment, and anaerobic, pectinolytic bacteria are
responsible for the decomposition of pectic substances and the subsequent release of fibre
(Akin et al. 2002). This process consistently yields high quality fibres (Van Sumere
1992). Chemical and enzyme retting offer substantially more control compared with dew
and water retting. Paridah et al. (2009) used 5% sodium hydroxide and 5% sodium
benzoate during retting of kenaf bast fibre and found that both methods produced fibres
of relatively lower tensile strength than those obtained with water alone. The colours of
chemically-treated bast fibre were also darker (Fig. 3). Song and Obendorf (2006) found
that enzymatic retting was the most suitable method to reduce the amount of lignin in
kenaf bast fibres. Yu and Yu (2007) removed 91.3% of pectin from kenaf bast fibre by
subjecting the bast fibres with enzyme from fungal strain isolated from the river where
the kenaf was retted. The optimal retting conditions used were: culture temperature 32C,
initial pH 6.0 of the culture medium, cultivation time 24 h, retting time 21 h, and
inoculation size 25%. Evans et al. (2002) studied an enzymatic retting of flax bast fibres
using several fungi and found that Aspergillius niger PGase resulted in 62% increase in
fine fibre yield without significantly affecting the strength as compared with that of
untreated and other fungal sources. Van Sumere (1992) reported that the bacterial
method is relatively better than chemical, because it gives better fibre quality and lower
pollution, whilst chemical retting requires high energy and generates costly wastes.

Enzymatic Retting
Microbial retting is not a new process. This traditional method is mainly achieved
by the pectic enzymes produced by bacteria. During retting, the bacteria multiply and
produce extracellular pectinases, which release the bast fibre from the surrounding cortex
by dissolving the pectin. Nowadays, with the advancement of biotechnology tools, such
enzymes can be commercially produced, thus making enzymatic retting a more popular
choice for the production of long fibres.



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Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5269
Table 7. Various Types of Retting Processes Used for the Production of Long Bast Fbers

Retting
types
Description


Advantages

Disadvantages Duration
of retting
Types of
bast
fiber
Referen-
ces



Dew
retting
Plant stems are cut
or pulled out and left
in the field to rot
Pectin material could easily be
removed by bacteria.
Reduced strength, low and
inconsistent quality;
restriction to certain climatic
change and product
contaminated with soil.

2-3
weeks
Flax, jute 1, 2




Water
retting
Plant stems are
immersed in water
(rivers, ponds, or
tanks) and monitored
frequently (microbial
retting)
Produces fiber of greater
uniformity and higher quality
Extensive stench and
pollution arising from
anaerobic bacterial
fermentation of the plant,
high cost and putrid odor,
environmental problems and
low-grade fiber.
Requires high water
treatment maintenance.

7-14
days
Flax,
Hemp,
kenaf,
jute





1, 3, 4, 5,
6, 7
Enzymatic
retting
Enzymes such as
pectinase, xylanases
etc. are used to
attack the gum and
pectin material in the
bast. The process is
carried out under
controlled conditions
based on the type of
enzyme.

Easier refining particularly for
pulping purposes that degrades
and provides selective
properties for different
applications. The enzymatic
reactions cause a partial
degradation of the components
separating the cellulosic fiber
from non-fiber tissues. The
process is faster and cleaner.


Lower fiber strength 12-24
hours
flax 1,8

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Table 1. Continued



Chemical
retting

Boiling and applying
chemicals normally
sodium hydroxide,
sodium benzoate,
hydrogen peroxide.

It is more efficient and
can produce clean
and consistent long
and smooth surface
bast fiber within a
short time.

The fiber retted in more than
1% NaOH the tensile strength
decreases. Unfavorable color
and high processing cost.



75
minutes-1
hour

Kenaf,
jute,
flax

9, 10
Mechanical
retting
Hammering or fibers
are separated by
hammermill or
decorticator.
Produces massive
quantities of short
fiber in short time
High cost and lower fiber
quality.
Kenaf 11

1
Van Sharma 1992;
2
Sharma and Faughey 1999;
3
Sharma 1987a;
4
Hongqin and Chongwen 2007;
5
Cochran, et al. 2000;
6
Banik et al. 2003;

7
Rome 1998;
8
Akin et al. 2007;
9
Kawahara et al. 2005;
10
Mooney et al. 2001;
11
Paridah and Khalina 2009.


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Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5271
Due to the long retting period, many efforts have been focused on studying the
degradation of pectic substances, lignin, and hemicellulose through enzymatic degrada-
tion (Akin et al. 2001; Goodman et al. 2002; Yu and Yu 2007; Lu et al. 1999; Mooney et
al. 2001; Sharma 1987). Pectic substances are abundantly present in the plant kingdom,
forming the major components of middle lamella, a thin layer of adhesive extracellular
material that separate fibres. The enzymes hydrolyzing these pectic substances are
broadly known as pectinases, and they can be produced by a wide variety of microbial
sources such as bacteria (Dosanjh and Hoondal 1996; Kapoor et al. 2000), yeast (Blanko
et al. 1999), fungi (Huang and Mahoney 1999; Stratilova et al. 1999), and actinomycetes
(Beg et al. 2000a). Enzymes are extremely efficient and highly specific biocatalysts
(Hoondal et al. 2002).
According to Lang and Donenburg (2000), microbial pectolysis is important in
the decomposition of plant by breaking down the pectin polymer. During degradation,
the plant polysaccharides can be attacked by several enzymes; however this process is
being intiated by pectic enzymes, as it is the most readily available. Hence this type of
enzyme has been used by many researchers for retting or degumming of plant fibres such
kenaf, ramie, flax, and hemp (Hoondal et al. 2002; Kapoor et al. 2000; Hongqin, and
Chongwen 2007) without significant damage to the fibres.


PROPERTIES OF BAST FIBRES PREPARED BY RETTING

Table 8 shows the characteristics of long bast fibers produced from hemp, jute,
flax, and kenaf obtained using different retting processes. Apparently, cellulose, hemi-
celluloses, and lignin are the main constituents of bast fibers. In addition, bast fibers also
include pectic materials, the main substance that binds the bast fibers together. The total
content of both cellulose and hemicelluloses are 98% for hemp, 80% both jute and flax,
while kenaf only has 71% of these polysaccharides. Flax and hemp also have the highest
values in fibre length and diameter but with least moisture contents compared to kenaf
and jute. These characteristics suggest the flax and hemp are good source of fibres for
textile applications rather than for composites (Zhang 2003). Conversely, kenaf has the
highest tensile strength among the four types of bast fibres. An earlier study carried out in
our laboratory using kenaf bast fibre with different retting process (water, sodium
hydroxide, and sodium benzoate) revealed that water retting gave the highest tensile
strength (Fig. 2).
As shown in Table 8, even though hemp was reported to give relatively higher
fibre yields, its quality is categorized as fair. On the other hand, kenaf produces
relatively high fibre yield, acceptable fibre morphology, and chemical content, as well as
good fibre quality, which make it more favourable to be used in the composite industry.
Kenaf apparently has better commercial value than do flax, hemp, and jute.

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Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5272

Fig. 2. Effect of pretreatment on the tensile strength of kenaf bast fiber
Kenaf Fibre Quality
To date, standards for fibre quality have been developed only for jute, kenaf, and
mesta. Being the most produced and used fibre, jute has its own grading system, which
was developed by the Bureau of Indian Standards and Bangladesh National Standards
Institution. There have been no official grades published for hemp and flax. Sur (2005)
carried out an extensive study on the quality of jute fibre in relation to its suitability for
yarn production and its behavior in the manufacturing process. Generally, the assessment
of fibre quality is based on their root content, colour, luster, fineness, length, elasticity,
strength (flexural and torsional rigidity), and moisture absorption, etc.
Basically, there are two types of kenaf fiber, kutcha for the local market and
pucca for export. Each category can be further classified, into five grades denoted by the
letters A to E, with A being the superior grade. Rowell and Stout (2006) recommend the
following characteristics as criteria to determine fibre quality:
Fibre strength
Cleanness and fineness
Color and luster
Length and percentage of cutting

The strength of the fibre is also assessed by snapping a few strands by hand, a
qualitative procedure that gives a useful indication to an experienced operator. Cleanli-
ness and freedom from non-fibrous matter is an important feature, and, in this respect, the
physical imperfections that may result from improper retting can have a profound effect
on the allotted grade. Color is irrelevant, but certain end-users traditionally prefer
particular colors of fibre for the sake of appearance. Luster is commonly an indication of
strength (Rowell and Stout 2006). All these properties would ultimately determine the
success of using these fibres in a fine, woven textile structure (Zhang 2003). In
commercial plants, many other factors, such as the following, will influence the fibre
quality:

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Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5273
Table 8. Characteristics of Long Bast Fibers Produced from Hemp, J ute, Flax, and Kenaf
Type Fiber chemical content

Tensile
strength
(mm)
Moisture
content %
Yield
(tonne/
hectare)
Retting
methods
Quality references
Fiber
Length
(mm)
Fiber
diameter
microns
Lignin
%
Cellulose
%
pectin Hemi
cellu-
lose %
Hemp 15-55 17-22.8 5-3 70-92 0.9 18-22 310-750 <15 8-18 Chemical
retting
Fair 5,7,10,14,1
5,16,17,18,
19,20,21
J ute 2-5 15.9-20.7 5-13 51-84 0.2 12-20 200-450 23 2-4 Dew retting Good 5,7,8,9
Flax 9-70 5-38 14-19 60-81 0.9 2.3 345-1100 10-12 1.4-2.5 Enzymatic
retting
Fair 2,5,7,9,10,
11,12,13
Kenaf 2.6-4 17-21.9 15-19 44-57 2 21 295-1191 10-20 2-4 Water
retting
Good 1,2,3,4,5,6
Source:
1
Misra (1987),
2
Mohanty et al. (2001),
3
Rowell and Han (2000),
4
Anon. (2001),
5
Perry (1975),
6
Carr et al. (2005),
7
Skorski (1963),
8
Gassan and Bleddzki (2001),
9
Rowell and Stout (1998),
10
Harders and Steinhauser (1974),
11
Alann Andr. (200)6,
12
Rowell and Han (2000),
13
Biogiotti and Kenny (2004),
14
Kozlowski (2000),
15
J oseph (2002),
16
Meier and Mediavilla (1998),
17
Mwaikambo and Ansell (2006),
18
Peston
(1963),
19
Hughes (2000, 1997),
20
Ronalli (1999), and
21
Mwaikambo (2002)



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Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5274
Variety
Different varieties have different fibre quality. Dempsey (1975) reported that the
fibre of kenaf varieties varies from 4 to 5% in the fresh plant. He also stated that the late
maturing group cultivars could produce better fibre than early maturing ones.

Environmental conditions
Favorable cultivation conditions could lead to better fibre quality. Kenaf grown
on alluvial soil has shown better fibre quality than that of plants grown on sand, which is
better than peat soil (Pate et al. 1954). Satisfactory levels of fertility, temperature, plant
density, and irrigation could improve the fibre quality (Dempsey 1975).

Harvesting
The highest quality fibre is obtained when kenaf is harvested during the beginning
of the flowering period (Duke and Ducellier 1993). Moreau et al. (1995) indicated that
fibre quality was obviously reduced after flowering. The period to achieve maturity
depends on the climate, for instance in a tropical region within 4 to 5 months, and sub-
tropical 5 to 6 months.

Retting process
While water seems to be the most suitable method to produce high quality fibre,
other methods such as a combination of chemical and enzymatic retting have been
reported to give excellent results. However this method is expensive and complex; thus it
cannot be applied in the rural areas. With the advancement of technology, it is hoped that
cheaper and more practical methods can be developed to generate better fibre quality
with less environmental pollution.

Utilization of Kenaf Fibre
Historically, kenaf fibre was first used as cordage. Industry is now exploring the
use of kenaf in papermaking and nonwoven textiles. Pulping kenaf fibres (bast and core)
can benefit the environment because generally lower amount of chemicals are required in
kenaf pulping than in wood pulping. Subsequently the discharge of spent chemicals is
less. Kenaf can be either pulped alone or blended with recycled paper (Liu 2003; Ahmed
et al. 2008). When it is used alone, one can produce high quality kenaf fibre suitable for
making specialty papers such as security paper, tea-bags, currency notes, etc. Kenaf
paper is stronger, whiter, longer lasting, more resistant to yellowing, and has ink
adherence better than wood paper (Liu 2003).
Kenaf has attracted attention in recent decades as an abundant natural fibre source
in the field of fibre reinforced composites. Many properties of the natural fibre-
reinforced composites were found to be comparable or superior to those of the corres-
ponding glass fibre-reinforced composites (Wambua et al. 2003). It was found that
tensile modulus, impact strength, and the ultimate tensile stress of the kenaf reinforced
polypropylene composites increases as the fibre content increases (Wambua et al. 2003).
In another study, liquefied kenaf core (LKC) has been used as a polyol to
synthesize polyurethane adhesive (LKCPU). The produced adhesive has shown great

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Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5275
potential as a wood laminating adhesive, particularly for edge-gluing (J uhaida et al.
2009).
Kenaf fibres also have a higher reinforcing effect on natural rubber compared
with that of synthetic polyester fibres (El-Sabbagh et al. 2001). Kenaf also has excellent
properties for reinforcing plastic composites as it has low density, no abrasion during
processing, high filling levels, high specific mechanical properties, and biodegradability.
On the other hand, polypropylene is a thermoplastic polymer, made by the chemical
industry and used in a wide variety of applications, including packaging, textiles (e.g.
ropes, thermal underwear, and carpets), stationery, plastic parts and reusable containers
of various types, laboratory equipment, loudspeakers, automotive components, and
polymer banknotes (Khalina et al. 2008a).
Kenaf natural fibre/plastic compounds are light and easy to process, and they
could replace glass-reinforced plastics in many cases. Kenaf compound panels have the
mechanical and strength characteristics of glass-filled plastics and at the same time, they
are less expensive and partially recyclable in many instances (Kano 1997). Therefore,
they can be used in the automotive (Khalina et al. 2008b), construction, housing, and
food package industries (Zhang 2003). Whole stalk kenaf can also be used in corrugated
paper medium and also in building materials such as particleboard (Paridah and J uliana
2008; Webber et al. 1999a) and medium density fibreboard.
Zhang (2003) found that blending cotton into pure kenaf yarn can increase the
yarns strength and elongation at break, and make the yarn less stiff. Paridah and Maziah
(2010) compared the properties of kenaf with those of similar fibres and concluded that
kenaf offers great potential as raw material for technical textile to partially replace the
synthetic glass and aramid fibres for making anti-ballistic materials. These applications,
however, have to follow strict fibre processing procedures, as well as modification of
fibre surface, which are quite complex and costly. Nonetheless, such procedures give
added value to the final products, i.e. five to six times higher than the price of an
unmodified kenaf stem.


CONCLUSIONS

Based on comparisons in production, anatomical properties, stem processing fibre
quality and prices, kenaf apparently has multiple advantages compared to hemp, jute, and
flax in tropical countries as a fibre source. Kenaf yields are greater than the others, hence
providing a more cost-effective raw material. Kenaf has the lowest aspect ratio, low
density, and relatively high tensile strength among other fibres. The retting method is the
predominant challenge in the application of bast fibres. The selection of retting method is
most important if the fibres are to be used in textiles. Studies have shown that the most
efficient method is by combining chemical and enzymatic retting. The future of bast
fibre crops relies mainly on the end uses of the fibres. The long bast fibres offer much
more domain of usage and hence offer the highest value, whilst short fibers from the
same plants can be used in a limited number of applications.



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Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5276
REFERENCES CITED

Ahmed, A. M., J alaluddin, H., Noor, I. S. A., and Harmaen, A. S. (2008). Suitability of
kenaf (Hibiscus cannabinus L.) soda-AQ pulp for manufacture of linerboard,
Proceedings Colloquium of kenaf Research out put 1-2 December 2008, Seremban,
Negeri Sembilan Malaysia Unversiti Putra Malaysia.
Akin, D. E., Condon, B., Sohn, M., Foulk, J . A., Dodd, R. B., and Rigsby, L. L. (2007).
Optimization for enzyme-retting of flax with pectate lyase, Ind. Crops Prod. 25,
136-146.
Akin, D. E., Foulk, J . A., and Dodd, R. (2002). Influence on flax fibre of components in
enzyme-retting formulations, TextileRes. J. 72, 510-514.
Alann, A. (2006). Fibres for strengthening of timber structures, Research report: 03,
http://www.google.com.my/#hl=en&&sa=X&ei=F1bATP6sOZL5cZqslJ oM&ved=0
CBQQvgUoAA&q, Accessed on 21.10.2010.
Anon. (2008). Food and Agricultural Organization of United Nations, Economic and
Social Department: The Statistical Division.
Anon. (2001). Kenaf-An alternative fibre crop, in Natural Life Magazine, International
Kenaf Association, pp. 42.
Anon. (2009). Low cost retting of jute/kenaf/mesta for quality up-gradation, Project
report CFC/IJ SG/24FT. J ute Corporation of India Ltd. (J CI) and Bangladesh J ute
Research Institute (BJ RI). 62 pp.
Anon. (2003). FAO Yearbook Statistic J uly 2003.
Banik, S., Basak, M. K., Paul, D., Nayak, P., Sardar, P., Sil, S. C., Sanpui, B. C., and
Gosh, A. (2003). Ribbon retting of jute - A prospective and ecofriendly method for
improvement of fibre quality, Ind. Crop. Prod. 17, 183-190.
Beg, Q. K. Bushan, B., Kapoor, M., and Hoondal, G. S. (2000a). Production and
chracterisation of thermostable xylanase and pectinase from a Streptomycetes spp.
QG-11-3, Res. Bull. Panjab Uni., Sci. 51, 71-78.
Biogiotti, J ., Puglia, D., and Kenny, J . M. (2004). A review on natural fibres based
composites - Part 1: Structure processing and properties of vegetable fibres, J. Nat.
Fib. 1(2), 37- 68.
Blanco, P., Sieiro, C., and Villa, T. G. (1999). Production of pectic enzymes in yeasts,
FEMS Microbiol. Lett. 175, 1-9.
Bangladesh National Standard Institution (BNSI), (2008). Grades of raw kenaf and
mesta fibre, Mahan Bhaban 116-A, Tejgaon I/A, Dhaka-1208, Bangladesh.
Bodig, J ., and J ayne, B. A. (1982). Characteristics of Wood Composites, Mechanics of
Wood and Wood Composites, Van Norstrand Reinhold Company, Inc., New York, 1-
47.
Calamari, T. A., Tao, W., and Goynes, W. R. (1997). A preliminary study of kenaf fiber
bundles and their composite cells, Tappi Journal 80(8), 149-154.
Chen, L., Columbus, E. P., Pote, J . W., Fuller, M. J . and Black, J . G., (1995). Kenaf bast
and core fibre separation, Kenaf Association, Irving, TX, pp. 15-19.
Chen, J ., Wang, L., and Thompson, L. U., (2006). Flaxseed and its components reduce
metastasis after surgical excision of solid human breast tumor in nude mice, Cancer
Lett. 234(2), 168-175.

PEER-REVIEWED ARTICLE bioresources.com


Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5277
Cochran, M. J ., Windham, T. E., and Moore, B. (2000). Feasibility of industrial hemp
Production in Arkansas.
Dempsey, J . M. (1975). Fibre Crops, Rose Printing Company, Tallahassee, FL.
Dosanjh, N. S., and Hoondal, G. S. (1996). Production of constitutive, thermostable,
hyperactive exopectinase from Bacillus GK-8, Biotechnol. Lett. 18, 1435-1438 .
El-Sabbagh, S. H., El-Hariri, D. M., and El-Ghaffar, M. A., (2001). Effect of kenaf
fibres on the properties of natural rubber vulcanizate, Polym. Polym. Compos. 9,
549-560.
FAO (2008). Food and Agricultural Organization of United Nations, Economic and
Social Department: The Statistical Division.
Gassan, J ., Chate, A., and Bledzki, A. K. (2001). Calculation of elastic properties of
natural fibres, J. Mater. Sci. 36(15), 3715-3720.
Goodman, A. M, Ennos, A. R., and Booth, I. (2002). A mechanical study of retting in
glyphosate treated flax stems (Linum usitatissimum L.), Ind. Crops Prod. 15, 169-
177.
He, S. J ., and Zhao, X. H. (1990). Study on paddy field retting of kenaf, China Plant
Fibres Product 33-46.
International J ute Study Group (IJ SG), (2003). Resources about jute, kenaf and roselle
plants.
J alaluddin, H., Ainun, Z. M., Mohamudin, S., and Harmaen, A. S. (2008).
Manufacturing of high water/moisture resistant products from kenaf (Hibiscus
cannabnius L.) fibre, Proceedings Colloquium of Kenaf Research output 1-2
December 2008, Seremban, Negeri Sembilan Malaysia Unversiti Putra Malaysia.
J oseph, S., Sreekala, M. S., Oommen, Z., Koshy, P., and Thomas, S. (2002). A
comparison of the mechanical properties of phenol formaldehyde composites
reinforced with banana fibres and glass fibres, Composite Science and Technology
62, 1857-1868.
J uhaida, M. F., Paridah, M. T., Mohd Hilmi, M., Sarani, Z., Mohamad Zaki, A. R., and
J alaluddin, H. (2009). Production of polyurethane from liquefied kenaf (Hibiscus
cannabinus L.) core for wood laminating adhesive, Master thesis, Universiti Putra
Malaysia, Serdang.
Kano, T. (1997). Development and prospect of kenaf board, Reference No. 47 of the
Kenaf Society of Kochi and economic reports of Ehime. 10, 25(44).
Kapoor, M., Beg, Q. K., Bushan, B., Dadhichm, B., and Hoondal, G. S. (2000).
Production and partial purification and characterization of a thermoalkali stable
polygalacturunase from bacillus sp MG-cp-2, Process Bichem. 36, 467-473.
Karus, M., and Kaup, M. (2002). Use of natural fibres in the Germany automotive
industry, http:/ /www.commonlink.com/~olsen/hemp/IHA.
Kawahara, Y, Tadokoro, K, Endo, R., Shioya, M., Sugimura, Y., and Furusawa, T.
(2005). Chemically retted kenaf fibres, Sen'i Gakkaishi 61, 115-117.
Khalina, A., Nor, A. I., Paridah, M. T., Syeed, S. O. A., Kamarul, A. H., and Ahmed, S.
A. (2008). Tensile properties of kenaf (Hibiscus cannabnius L.) fibre reinforced
polypropylene composites using twin screw extruder, Proceedings Colloquium of
kenaf Research out put 1-2 December 2008, Seremban, Negeri Sembilan Malaysia
Unversiti Putra Malaysia.

PEER-REVIEWED ARTICLE bioresources.com


Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5278
Khalina, A., Nazri, A. M., and Hasniza, M. Z. (2008). Simulation studies of fibre
reinforced plastic composite on injection moulding processing for automotive
application, Proceedings Colloquium of kenaf Research out put 1-2 December 2008,
Seremban, Negeri Sembilan Malaysia Unversiti Putra Malaysia.
Kozlowski, R. (2000). Potential and diversified uses of green fibres, Third International
Wood and Natural Fibres Composites Symposium, 19th -20th September, Kassel,
German, 1-14.
Kymalanen, H.-R. (2004). Quality of Linum usitatissimum L. (flax and linseed) and
Cannabis sativa L. (fibre hemp) during the production chain of fibre raw material for
thermal insulations, Academic dissertation, MMTEK Publications 17, University of
Helsinki.
Ladunki, O. (1994). Poradnik encyklopedyczny, Polskie Towarzystwo
Towaroznawcze, Oddia Morski, Sopot.
Lamb, R. P., and Denning, J . R. (2004). Flax cottonised fibre from linseed stalks, A
report for the Rural Industries Research and Development Corporation.
Lu, S. S., Huang, X. B., and Chen, J . H. (1999). Study on anaerobic microbe retting of
kenaf in China, J. China Text. Univ. 25(6), 107-110, 114.
Misra, D. K. (1987). Cereal straw, pulp and paper manufacture, Vol. 3, Secondary
Fibres and Nonwood Pulping.
Mohanty, A. K., Misra, M., and Drzal, L. T. (2001). Surface modifications of natural
fibres and performance of the resulting biocomposites, An overview, Composite
Interfaces 8(5), 313-343.
Mooney, C., Stolle-Smits, T., Schols, H., and de J ong, E. (2001). Analysis of retted and
non retted flax fibres by chemical and enzymatic means, Journal of Biotechnology
89, 205-216.
Moreau, J . P., Bel-Berger, P., and Tao, W. (1995). Mechanical processing of kenaf for
nonwovens, TAPPI Journal 78(2), 96-105.
Mwaikambo, L.Y., Ansell, M. P., and Kawiche, G. M. (1999). Development of natural
fibre composites, An overview workshop on Materials selection and design,
International Centre for Science and High Technology, Trieste, Italy, 15th-19th
November.
Mwaikambo, L. Y. (2002). Plant-based resources for sustainable composites, PhD
Thesis, University of Bath, Department of Engineering and Applied Science, Bath.
Mwaikambo, L. Y., and Ansell, M. P. (2006). Mechanical properties of alkali treated
plant fibres and their potential as reinforcement materials, Part I. Hemp fibres,J.
Mater. Sci. 41, 2483-2496.
Oliver, AL., and Howard, J . (1999). Industrial hemp fact sheet, British Columbia
Ministry of Agriculture and Food, Kamloops, British Columbia, Canada, 20 pp.
Oplinger, E. S., Oelke, E. A., Doll, J . D., Bundy, L. G., and Schuler, R. T. (1989).
Alternative Field Crops Manual, Flax, University of Minnesota.
Perry, D. R., (1975). Identification of Textile Materials, The Textile Institute, Manara
Printing Services, London.
Paridah, M. T., Syeed, S. A., and J uliana, H. (2008). Mechanical properties of kenaf
(Hibiscus cannabnius L.) stem of different ages, Proceedings Colloquium of kenaf

PEER-REVIEWED ARTICLE bioresources.com


Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5279
Research out put 1-2 December 2008, Seremban, Negeri Sembilan Malaysia
Unversiti Putra Malaysia, 18 pp.
Paridah, M. T., and Khalina, A. (2009). Effects of soda retting on the tensile strength of
kenaf (Hibiscus cannabnius L.) bast fibres, Project Report Kenaf EPU, 21 pp.
Pate, J . B., Seale, C. C., and Gangstad, E. O. (1954). Varietal studies of kenaf, Hibiscus
cannabinus L. in south Florida, Agronomy Journal 46, 75-77.
Pan, A., Yu, D., Demark-Wahnefried, W., Franco, O. H., Lin, X. (2009). Meta-analysis
of the effects of flaxseed interventions on blood lipids, Am. J Clin. Nutr. 90(2), 288-
297.
Lamb, P. R., and Denning, R. J . (2004). Flax cottonised fibre from linseed stalks, a
report for the Rural Industries Research and Development Corporation.
Preston, R. D. (1963). Observed structure in plant fibres, Fibre structure, In: Hearle, J .
W. S., and Peters, R. H. (eds.), Butterworth & Company and The Textile Institute,
London, 235-268.
Ranalli, P. (1999). Advances in Hemp Research, Haworth Press, 272 pp.
Ramaswamy, G. N., and Boyd, C. R. (1994). Kenaf as a textile fibre, processing, fibre
quality, and product development, In: Goforth, C. E., and Fuller, M. J . (eds.). A
Summary of Kenaf Production and Product Development Research, Mississippi State
University Bulletin, 1011, pp. 31-33.
Rowell, R. M., and Han, J . S. (1999). Changes in kenaf properties and chemistry as a
function of growing time, In: Kenaf Properties, Processing and Products,
Mississippi State University. Mississippi State, MS., pp.32-57.
Riccio, F. A., and Orchard, L. P. (1999). Nonwood fibre resources: Availability,
infrastructure, and feasibility, In Fifth International Conference on Woodfibre-
Plastic Composites, Forest Products Society, Madison, Wisconsin, May 26-27, 1999,
ISBN 0-892529-07-6.
Robson, D., Hague, J ., Newman, G., J eronimidis, G., and Ansell, M. P. (1993). Survey
of natural materials for use in structural composites as reinforcement and matrices,
Natural materials for composites, EC/4316/92, The Biocomposites Centre,
University of Wales, Bangor, 1-71.
Rome (1998). Improved retting and extraction of jute project findings and
recommendations international jute organization fao/government cooperative
programmed, Food and Agriculture Organization of the United Nations.
Rowell, R. M., and Stout, H. P. (2006). J ute and kenaf, in: Handbook of Fibre
Chemistry, Lewin, M. (ed.), CRC Press, an imprint of Taylor & Francis Group, an
Informa business, Chapter 7.
Rowell, R. M., and Stout, H. P. (1998). J ute and kenaf, in: Handbook of Fibre
Chemistry, 2nd Edition, Lewis, M., and Pearce, E. M. (eds.), Marcel Dekker, New
York, 465-504.
Rowell, R. M., and Han, J . S. (2000). Characterisation and factors effecting fibre
properties, Natural Polymers and Agrofibres Composites, Frolini, E., Leao, A. L.,
and Mattosso, L. H. C. (eds.), San Carlos, Brazil, 115-127.
Rymsza, T. A. (2000). Advancements of kenaf in the USA- Kenaf paper and nonpaper
developments, Paper presented at International Kenaf Conference, October 13-14,
2000, Hiroshima. J apan Kenaf Association, pp. 10.

PEER-REVIEWED ARTICLE bioresources.com


Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5280
Wood, I. (2000). Fibre Crops - New Opportunities for Australian Agriculture, CSIRO
Sanadi, A. R., Caulfield, D. F., and J acobson, R. E., (1997). Agro-fibre/thermoplastic
composites, in R. M. Rowell, R. A. Young, and J . K. Rowell (eds.), Paper and
Composites from Agro-Based Resources, CRC Lewis Publishers, Boca Raton, FL. pp.
377-402.
Sharma, H. S. S., (1987). Studies on chemical and enzyme retting of flax on a semi-
industrial scale and analysis of the effluents for their physicochemical components,
International Biodeterioration 3(6), 329-342.
Sharma, H. S. S., and Faughey, G. J . (1999). Comparison of subjective and objective
methods to assess flax straw cultivars and fibre quality after dew-retting, Ann. Appl.
Biol. 135, 495-501.
Sikorski, J . (1963). The fine structure of animal and man-made fibres, Fibre structure,
Hearle, J . W. S., and Peters, R. H. (eds.), Butterworth & Company and The Textile
Institute, London, 269-310.
Stratilova, E., Breierova, E., and Vadkertiova, R. (1996). Effect of cultivation and
storage pH on the production of multiple forms of polygalacturunase by Aspergillus
niger, Biotechnol. Lett. 18, 41-44.
Sur, D. (2005). Understanding Jute Yarn, Institute of J ute Technology. Anindita Sur,
Kolkata, pp. 254.
Smeder, B., and Liljedahl, S., (1996). Market oriented identification of important
properties in developing flax fibres for technical uses, Industrial Crops and Products
5, 149-162.
Van Sumere, C. F. (1992). Retting of flax with special reference to enzyme retting, In:
Sharma, H. S. S., and Van Sumere, C. F. (eds). The Biology and Processing of Flax,
Publications, Belfast, Northern Ireland, 157-178.
Tavisto, M., Pasila, A., Pehkonen, A., Lahtinen, S., Lindsten, L., and Reunanen, N.
(2001). Flax in MFT packages, University of Helsinki. Publications of Department
of Agricultural Engineering and Household Technology 6. 65 p. Helsinki. (in
Finnish).
The Golden Fibre Trade Centre Limited, (GFTCL) - Articles & Information on J ute,
Kenaf, & Roselle Hemp
Thygesen A., (2005). Properties of hemp fibre polymer composites an optimization of
fibre properties using novel defibration methods and detailed fibre characterisation,
Ph.D. thesis, Ris National Laboratory, Denmark.
Thompson, L. U., Chen, J . M., Li, T., Strasser-Weippl, K., and Goss, P. E. (2005).
Dietary flaxseed alters tumor biological markers in postmenopausal breast cancer,
Clin. Cancer Res. 11(10), 3828-3835.
Upfold, R. A. (1976). Revision of Factsheet "Flax in Ontario", University of Guelph;
D. J . Hume - University of Guelph.
Van Sumare, C. (1992). Retting of flax with special reference to enzyme-retting, In:
The Biology and Processing of Flax, Sharma, H., and Van Sumare, C. (eds.), M
Publications, Belfast, Northern Ireland, 157-198.
Voulgaridis, E., Passialis, C., and Grigoriou A. (2000). Anatomical characteristics and
properties of Kenaf stems (Hibiscus cannabinus), IAWA Journal 21(4), 435-442.

PEER-REVIEWED ARTICLE bioresources.com


Tahir et al. (2011). Review of bast fiber retting, BioResources 6(4), 5260-5281. 5281
Wambua, P., Ivens, J ., and Verpoest, I. (2003). Natural fibres: Can they replace glass in
fibre reinforced plastics, Composites Science and Technology 63(9), 1259-1264.
Yu, H., and Yu, C. (2007). Study on microbe retting of kenaf fibre, Enzyme Microb.
Tech. 40, 1806-1809.
Zhang, J ., Henriksson, H., Szabo, I. J ., Henriksson, G., and J ohansson, G. (2005). The
active component in the flax-retting system of the zygomycete Rhizopus oryzae sb is
a family 28 polygalacturonase, J. Ind. Microbial Biotechnol. 32, 431-438.
Zhang, T. (2003). Improvement of kenaf yarn for apparel application, Master thesis of
Louisiana State University, US.

Article submitted: October 12, 2010; Peer review completed: Dec. 26, 2010; Revised
version received and accepted: August 13, 2011; Published: Sept. 5, 2011.