A. Gums for food uses
B. Technological grade gums
Plant gums are adhesive substances that are carbohydrates in nature and are usually produced as exudates from the bark of trees or shrubs. Some plant gums, such as gum arabic are soluble in water, dissolving to give clear solutions. Others including gum tragacanth produce mucilages by absorbtion of large quantities of water.
Plant gums originating from many
countries have been an important item in international trade for centuries in food,
pharmaceutical, paper textile and other industries. Depending upon their major use, plant
gums may be broadly classified as 'food' and 'non-food' or 'technological grade' gums. The
former can be used as food additives in various kinds of confectioneries, foods and
beverages and include gum arable, gum tragacanth, gum karaya and gum carob. The latter
category finds its major use in non-food industrial applications and include 'gum ghatti',
'gum talha' and a variety of other gums.
1. Gum arabic
2. Gum tragacanth
3. Gum karaya
4. Carob gum
1.1. Product description
1.8. Prospects and recommendations
Gum arabic or gum acacia, locally known as gum 'hashab', is the most widely used and traded of the true water soluble gums. True gum arabic is produced by Acacia senegal only, but gums obtained from other Acacias are also sometimes, though erroneously, referred to by the same name. There has been a tendency by Indian authors, in particular, to specify Acacia arabica as the source of gum arabic (e.g Verma, 1988, Gupta and Guleria, 1980). The gums from A. arabica and over 120 other Acacia species have been shown to differ greatly from gum arabic in terms of chemical composition and structure (Anderson, 1993).
Gum arabic came to medieval Europe
through Arabs, hence the name, gum arable. Its organized trade started in Sudan in 1820
(Awouda, 1988), which still dominates the world gum arabic production to the extent of
70-80 percent and produces the best food stuff grades. Other gum arabic producing
countries are Chad, Senegal, Nigeria, Tanzania, Mali and Mauritania. It is exported as a
primary product to industrial countries, mainly western Europe and the USA.
Its main food-related uses are in
confectionery, soft and alcoholic beverages. Its non-food applications include
pharmaceutical, cosmetic, lithographic and offset preparations. It was extensively used as
an adhesive, but this use has almost entirely yielded to synthetics. Similarly its uses as
a sizing and finishing material in the textile industry have also mostly given way to
modern substitutes. However, small quantities continue to be used in paper making. The gum
is also used to a limited extent in polishes, contact insecticides and pesticides,
photographic emulsions and pharmaceuticals.
A tree, on an average, may yield 250
grams of gum arabic per annum, although production may range from a few grams to as high
as 10 kg (NAS, 1979) or 0.2 to 6.7 kg (Duke, 1981). The highest yields are observed on
individuals aged from 7 to 12 years. In general, the higher the average temperature, the
higher the yield of gum. Yield per ha per year ranges between 30 to 40 kg in case of open
stands and as much as 100 kg in case of dense stands (ITC, 1983).
Current production potential is
around 30,000 to 40,000 tonnes per annum, of which bulk (80%) originates in Sudan; Nigeria
being the second largest producer. Virtually all gum arabic in the Sahelian zone is
exported, either immediately or after a period of storage or stockpiling. Sudan dominates
the world exports, accounting for 70% to 80%, the balance being accounted for by the
Sahelian countries of West Africa (Nigeria, Mali, Niger, Burkina Faso, Chad, Tanzania and
The gum collectors transport their
produce by animals or tractors to one of the 13 auction markets in the country. Auction is
initiated by a government clerk at a minimum opening price and sale is settled at the
highest bid. Only officially approved merchants can buy the gum. Grading is done by teams
of local girls in the purchasers' sheds. The gum, packed in 50 or 100 kg burlap bags is
then sent over 1,000 miles by truck or rail to Port Sudan on the Red Sea for storage until
its eventual export by the Gum Arabic Company, the sole permitted exporter. An average
stock of 15,000 tonnes of gum arabic is maintained by the company at Port Sudan, from
where it is shipped to approved agents, processors and re-sellers world over.
Sudan has a well established grading system for gum arable, the main grades being as follows (Robbing, 1988 and Awouda, 1988):
i. Hand-Picked-Selected or HPS (Selected Sorts): uniformly shaped, medium sized and light coloured nodules.
ii. Cleaned and Sifted (Clean Sifted Sorts): The irregular shaped or darker-coloured nodules together with clean fragments.
iii. Cleaned (Cleaned Amber Sorts)
After segregating the first two grades manually, the remaining gum along with pieces of bark, dust etc. is broken by beating with sticks. It is then winnowed, impurities separated and removed. The residue is then sifted. The portion remaining in the sieve is known as gum sifting and what passes through the sieve is gum dust. Under existing arrangements grading is done by the merchants and the producer plays no role in it. This simple grading system is easy to teach to the producers who should be encouraged to adopt it to their advantage. The prices may then be fixed by grades. The top grades are eagerly sought for food, beverages and pharmaceutical applications.
Gum arabic may be further processed in the destination countries into forms needed for incorporation into the final products. These processes include 'kibbling' (making uniform pebble size pieces), granulating, powdering and spray-drying. About half of the usage of gum arabic is in sun-dried form. An additional third is in crude form, especially for confectionery applications. Powdered and granulated grades as well as some siftings make up the balance.
Sudan has recently established a
spray drying plant at Khartoum to encourage export of value added powdered gum arable.
Despite steadily decreasing demand over the past 15-20 years, gum arabic still remains a major natural exudate of commerce. Gum arabic sales had increased throughout the 1960s, reaching a peak around 1970 at approximately 70,000 tonnes. But the severe Sahelian droughts of 1973-74 led to a world shortage and high prices. This resulted in an impetus for some of the major users to shift over to the newly developed modified starches. Consequently, annual sales of gum arabic never exceeded 40,000 tonnes again, a plateau reached during 19781982 was followed by another even more severe drought in 198385. Consequent disruption in supplies forced many more companies to shift irreversibly to reformulations of their products based on synthetic products. The sales could not exceed 20,000 to 24,000 tonnes per year, even after adequate gum arabic stocks became available in 1986.
Current worldwide consumption is around 25,000 tonnes, of which about 20,000 tonnes comes from Sudan. The remaining 5,000 tonnes originates from other African nations, the majority of which, between 3000 and 4000 tonnes, comes from Nigeria 1.
1 Chemical Marketing Reporter, February 15 1993: pp 18-19.
The United States is the largest single market for gum arabic annual consumption, accounting for 25 percent of the world market. The European Community, Switzerland and Scandinavia collectively account for 40 percent of the world purchases of gum arable. About 10% is channelled into Japanese markets. Some countries like USA, France, West Germany and United Kingdom are important entrepots and large quantities of gum are re-exported.
In Sudan export prices are fixed by the Gum Arabic Company. Current gum arabic prices (US$ per tonne) are as follows ²:
No. 1 cleaned
No. 2 cleaned
² The Public Ledger's Commodity Week, July 1993.
The prices of 'Hand-Picked Selected' (HPS) are about 15 percent more than the cleaned grade. The price of the 'Cleaned and Sifted' is usually mid-way between those of the 'HPS' and 'Cleaned' grade.
The cost of handling gum arabic from origin to destination is typically in the range of US$ 120-200 per tonne including insurance, the lower end of the range being mainly destined to European markets, the higher end to more distant destinations such as the United States and Japan.
1.7.2. Trading structures and procedures.
Sudan's internal trading structure has already been discussed in section 1.5. The Gum Arabic Company (GAC), which is approximately one-third public owned and two-thirds privately owned, has a statutory monopoly in the export of gum from Sudan. Prices are fixed by the GAC every year. Illicit cross border trade, mainly to Chad, readily takes place whenever local traders judge that the prices fixed by the GAC are not competitive, and that the advantages outweigh the risk. The company has a warehouse capacity of 60,000 tonnes. The international buyers generally have confidence in the GAC's trade policy and integrity.
The gum arabic trade in the West African countries is far less structured than in the Sudan, a fact which militates against user's confidence. Trade in these countries is entirely in private hands.
There exists no international commodity agreement for any of the plant gums including gum arable. They are also not covered by any standards issued by the British Standards Institution (BSI) or the International Organisation for Standardization (ISO). Specifications for some of the gums are, however, given in various pharmacopoeias. Gum arabic's toxological status is 'Acceptable Daily Intake (ADI) Non-Specified' by GEFCA and EEC, indicating that it may be used without restriction additive up to a maximum of 2% of the final product. Food grade gum is recognized as 'GRAS' (Generally Recognized as Safe) in the USA.
Quality of gum arabic shipped from
Sudan has lately improved through local mechanical sorting and processing, which renders
the quality of shipments more uniform. A quality control laboratory has also been
established at Port Sudan with the help of UNCTAD/GATT (ITC), where chemical grading of
the product will be attempted. There is also an ongoing project to establish a 'kibbling
operation' to powder and spray dry the gum at Port Sudan to promote value added exports.
The major causal factor in the reduction in tonnages involved in international gum trading in recent years has been the uncertainty of regular supplies primarily because of drought. There is, therefore, an urgent need to stabilise the production base to preclude another catastrophe of a similar nature. This necessitates extensive planting of A. senegal not only for gum production, but also for ecological reasons. The tree also produces firewood, food and fodder.
There is always possibility that some, at least, of the gum can be collected will be marketable, especially if more systematic and wide spread production decrease prices, hygiene and storage standards improve, research identifies new uses of natural gums, and marketing strategies of Sudan are improved with a reduction in the present high rate of export tax (40%). When the tree must be planted for essential ecological reasons, and when the unique secondary products from these trees can earn essential overseas currencies, it is poor business practice if these overseas earnings are not maximised. The recent trend in use of natural foods may also tilt the balance in favour of the natural gums including gum arable.
Not so long ago, sale of the gums collected by nomads and villagers in Africa constituted their major single source of annual income; gum trees were treasured possessions and fights to death to retain ownership were not infrequent. Nowadays the nationalised policies of fixed farm gate prices often act as a disincentive for the gum collectors.
There is a need to integrate cultivation of A. senegal trees within the existing farming systems in the region through agro-forestry projects, in order to develop a strong and sustainable gum production base. Trees yielding higher quantities of gums should be selected for this purpose, and methods of gum collection should be improved. This will necessitate research into better understanding of the physiology of gum production. Unfortunately no research input has so far been provided by the gum producing countries.
Efforts on the supply side to breed new varieties of Acacia senegal that fit in agro-forestry systems and provide gum with especially desirable properties should ensure source diversification and a stable supply base to provide new dimensions to the end-uses. Current initiatives to invest in large scale plantations of A. senegal along with extension and training programmes both by the Gum Arabic Company and the international donors is welcome to overcome the problem of erratic supplies.
Research in new applications is opening up new opportunities. New beverage innovations, such as wine coolers, novel confectionery coatings, high fibre drinks and powders, and synergistic combination with other gums are some of the examples of new product formulations using gum arable. New patents using gum arabic in confectionery coatings and lithography have been recently granted. Funding for further research into new uses has been made available by both the Gum Arabic Company and international aid organizations. The introduction of more advanced quality control and grading/sifting/cleaning operations in the Sudan should further standardise gum arabic supplies, allowing for more efficient gum processing and more specific gum grades, readily available directly from the origin.
The latest marketing initiative by
the GAC in the shape of a beautiful brochure captioned 'Gum Arabic - an ancient
ingredient for the 21st century (1993)', if continued will build up confidence of the
importers and end-users of gum arable.
2.1. Product description
2.3. Collection and processing
2.7. Prospects and constraints
Gum tragacanth is the second most
important commercial gum and is produced by several shrubby plants of the genus Astragalus,
growing from Pakistan to Greece, particularly in Iran and Turkey (Anderson, 1989). A.
gummifer was considered to be the main tragacanth yielding species, but a field survey
has established that A. microcephalus is the principal source of the gum (Dogan et
al, 1985). The exudate is produced spontaneously on the bark of the shrub, but the yield
is often increased by making an incision and driving wooden wedges into it.
It is one of the oldest gum known and its use has dated back from pre-Christian times. It is widely used in pharmaceuticals and cosmetics: as a thickening agent in syrups, salad dressings and sauces; in textile sizing; and as an adhesive. It dissolves readily in cold water to give a solution of very high viscosity which is additionally highly resistant to strong acidic conditions, and the gum is therefore used primarily as a stabiliser and thickener in acid preparations.
The best quality gum is tasteless,
whitish, yellowish or pale-brown in colour and translucent in appearance. The lower grades
are generally more strongly coloured than the higher grades. The gum is obtained in two
basic physical forms, namely ribbons (superior quality) and flakes (inferior quality).
These two forms are obtained from different sub-species of the shrub. Both types of the
shrubs normally do not grow in the same locality (Robbing, 1988). The best type of gum is
obtained from artificial incisions rather than from natural exudations. Abundant rainfall
prior to the tapping season, and dry conditions during the harvesting season, constitute
optimum climate for gum production.
Plants are widely scattered and gum
is usually collected unsystematically by villagers. Gum production is labour intensive and
is carried out from remote hostile areas of Iran and Turkey. After collection the gum is
cleaned and selected by hand into five 'ribbon' (superior quality) and five flake
(inferior quality) grades, which may range in price from US$ 10 to 62 per Kg (Anderson,
1993). The best quality gum is of Iranian origin.
Iran and Turkey are the main producing countries, about 70 percent of the supplies originating from Iran alone. Iran's average annual production potential has been estimated at 400 tonnes ³. The gum is also known to be produced in Afghanistan and Syria, but export consignments are very rare.
³ Agricultural Products,
Iran's export of tragacanth was 91 tonnes in 1987, which with a growth rate of 56% reached 142 tonnes in 1988. The export volume further increased to 176 and 257 tonnes in 1989 and 1990, respectively. Thus, there had been an increase of 182% in 1990, over what was exported in 1987. With this growth rate, it is expected that Iran may very soon be able to export 400 tonnes of the product. Turkey is the second largest producer and exporter. Exports from Brazil and India are actually re-exports (Robbing, 1988).
Tragacanth finds markets in many
different countries, but the European Community, the United States, Japan and former
Soviet Union are the major importing regions.
Current prices ($/Lb) of gum tragacanth in New York Market are 4:
No. 1, ribbons
36.00 to 40.00
12.50 to 14.00
4 Chemical Marketing
Reporter, June 21 1993.
Demand for gum tragacanth fell greatly during 1980s, from several thousand tonnes to 200-300 tonnes per year, for several reasons. Iran/Iraq war made supplies erratic. The Iranian government tried to fix price that made the gum non-competitive and high inflation rates in Turkey had the same effect. In addition, demand for gum tragacanth fell suddenly and drastically after xanthan gum, a fermentation derived product developed in the 1970s, was finally approved for food use. Gum tragacanth has unacceptably high microbial contamination levels, previously controlled through fumigation with ethylene oxide (ETO). This process was forbidden around 1987, because of carcinogenicity of ETO. The alternative methods of bringing down the microbial counts also cause chemical changes in the gum and accordingly are not acceptable (Anderson, 1993).
Iran's recent recovery in tragacanth export market suggests that with a correct understanding of the world tragacanth market and supply of premium product there lies vast prospect for securing a bigger and better market for gum tragacanth.
Deliberate cultivation of gum
producing Astragalus species may be rewarding in appropriate regions. However,
little is known about genetic factors that enhance gum yield and quality.
3.1. Product description
3.3. Collection and marketing
3.8. Problems and prospects
Gum karaya also known as Indian
tragacanth is obtained almost exclusively from Indian plantations of Sterculia urens
and smaller plantations of S. villosa. In Sudan, and elsewhere in Africa, gum
karaya can be obtained from S. setigera. The exudates from these three species are
very similar in chemical composition and physico-chemical characteristics. Accordingly, in
terms of current legal definitions of identity and trade specifications, exudates from any
Sterculia, or admixtures, can be offered for sale.
Of all the gum karaya produced only
10% is used as a food additive; the remainder goes into pharmaceutical products (Anderson,
1993). The pharmaceutical applications of gum karaya include medical colostomy bag
fixings, dental fixatives and bulk laxatives. Colostomy bag fixings is the most common use
of gum karaya, in which the gum's qualities are difficult to equal. Its use in, dental
fixatives started declining when research showed that habitual use of acidic gum karaya
had an adverse effect upon any remaining natural teeth. Its principal food applications
include ice creams, ice pops, sherbets and salad dressings. Gum karaya is classified as
'Generally Recognised As Safe' (GRAS) within the USA for use up to specified upper limits
and in specified food products and as 'Acceptable Daily Intake (ADI) Not Specified' by the
joint FAO/WHO Expert Committee on food additives (JECFA). At present Scientific Committee
for Food of the EEC, in contrast, restricts the human intake of gum karaya (E416) to an
upper limit of 12.5 mg per kg body weight per day, but it has never been permitted in
Germany for its food applications (Anderson, 1993).
Villagers living in the vicinity of
forests are engaged for collection of the gum. A common method is to make blazes on the
tree trunk with some sharp edged tool. The gum begins to exude as soon as the blaze is
made and exudation continues for many days. Exudation is better in hot months from March
to May/June. No tapping is done in rainy season. The yield of gum varies from 1 to 5 kg
per tree per season, depending upon many factors (Verma, 1988). Due to indiscriminate and
unscientific tapping the trees often die. Although improved tapping method has been
developed, it has not been put in practice. Gum collected by the villagers is delivered to
the agents appointed by the trading corporation at rates fixed according to quality of
gum. It is then packed in gunny bags and transported to towns. Freshly cut gum often
contains moisture and sticks to the bags which brings down its quality. The gum often
contains many impurities like tree bark etc.
At the grading centre the big lumps
are broken into small pieces of about 1 to 3 cm in diameter. The broken pieces are then
graded manually in five different grades, which are registered with the Indian Agmark
organisation, and which are based mainly on criteria of viscosity, colour and freedom from
external bark, sand etc. The graded gum is packed in heavy duty bags of about 80 kg each.
Sometimes the gum is powdered and packed in 5 to 6 kg kraft paper bags or 75 to 100 kg
World production of gum karaya is
currently at about 5,500 tonnes per annum and is on a declining trend. India is the only
regular producer, overwhelmingly dominating international trade in the gum. Indigenous
consumption of gum karaya is very little, only lower grades are consumed in the country.
India is the main exporter. The United States consumes roughly one-half of gum karaya, and western Europe around 30%. There is significant re-export trade from European ports. Consumption in the United states is roughly stable, whereas in Europe there is evidence of some decline. (Robbing, 1988). Exports are controlled largely by a large number of long-established merchants based in Bombay. During 1991-92, India exported 573.6 tonnes of gum tragacanth, mainly to Japan, France, USA, West Germany, UK, Belgium, Italy, UAE and Netherlands, in that order. Total value of export was about 49 million Indian Rs. or an average price of Rs. 85,337.44 per tonne 5.
5 Monthly Statistics of
the Foreign Trade of India (1991-92), Directorate General of Commercial Trade and
Statistics, Govt of India.
The following are the current wholesale market prices (US$/Lb) for Karaya gum at New York 6:
No. 1 powdered
3.25 to 4.25
No. 2 powdered
No. 3 powdered
6 Chemical Marketing
Reporter, June 21 1993.
Government has closed some forests
for gum collection on the basis that it damages trees, although gum collection is done
from mature trees. The collectors should instead have been given training in proper
tapping techniques. Government has also started to control exports, and prohibited private
Bombay merchants from shipping gum karaya on the ground that they were making greater
financial gains than the tribal populations who tapped the trees and collected the gum.
The importers, however, had more confidence in the private merchants. The government
exports through National Association for Export Development (NAFED) were attempted at
higher farm-gate prices. These events coincided with an upsurge in availability of
substitutes and stimulated replacement of gum karaya. In 1989, NAFED was replaced by an
another Indian government agency, Tribal Development Federation (TRIFED) to regulate trade
in gum karaya, and a certain amount of trading was restored to the traditional Bombay
merchants (Anderson, 1993).
4.1. Product description
4.6. Prospects and constraints
Carob or locust bean gum is obtained
from the endosperm of the beans of carob tree (Ceratonia siliqua), which
grows in abundance in mediterranean region. The tree starts to bear economic quantities of
pods at the age of 15 years and may not be fully grown until it is 50 years old. The pods
reach full size in July, but are left until October to ripen. Hot dry weather is needed
for good yields. The gum is extracted from the endosperm of the seed kernels; the yield of
gum does not exceed 3% of the original weight of beans collected. Careful processing is
required to get gum of good colour and viscosity. Large trees can yield 0.5 tonne of pods
Carob gum has high viscosity in solutions at low concentrations, but requires heat application for full solubility in water. It is used mainly in food industry as a texturiser in ice-cream, pet foods, canned pet foods, and cream cheeses; as a thickener in instant soups; and to impart a range of desirable characteristics in various savoury, dessert and diary products.
Its non-food uses are of very minor
Spain, Italy and Portugal are the
main producing and trading countries, best quality gum being produced in Italy and
Portugal. Other known producing countries are Morocco, Greece, Cypress, Algeria, Turkey,
Israel, India and Pakistan. Production statistics on locust bean are not available.
Total world exports of locust bean gum are currently about 12,000 tonnes per annum, of which over 80 percent is attributable to Spain, Italy and Portugal in that order, the balance originating from countries in North-West Africa and the eastern Mediterranean (Robbing, 1988). Total World production, however, may be considerably higher because of consumption at sources.
The main consuming countries or
regions are Western Europe, the United States and Japan in that order, together accounting
for 75 percent of consumption of traded gums.
Current wholesale price for carob gum powder at New York market has been quoted as US$ 4.75 to 5.00 per Lb 7.
7 Chemical Marketing
Reporter, June 21 1993.
Locust bean pods were for a very
long time used as a cattle feed. This use has, however, declined considerably in some of
the major producing countries. This has reduced the economics of collecting locust tree
beans, hence affecting supplies of the gum and causing a price rise during the 1980s.
Consequently, Eastern Mediterranean and other developing countries, where carob trees
already exist and labour is cheap, have a chance to enhance production and capture the
market. This trend is already visible in Moroccan exports. Whereas no carob gum was
exported from Morocco during 1987 and 1988, it started exporting in 1989, when 1844 tonnes
in 1989, valued at of 28 million Dirhams were exported.
1. Gum talha
2. Gum combretum
Many trees yield gums that are not
permitted in food stuffs. Such gums are always in over supply and command low prices of
only US$ 750-850 per tonne only. These gums find a wide range of technological
applications such as printing inks, some lithographic applications, textiles, foundry and
Gum Talha is a water soluble gum derived from a number of Acacia species like A. seyal, A. sieberana, A. hockii, A. ehrenbergiana and A. karroo. All these species yield poor quality gum usually dark, with a high tannin content and of poor solubility. 'Gum talha' is in effect, simply a generalised trade description for water soluble gum from any Acacia species other than A. senegal (Anderson 1993) and is a major source of technological grade gums. It is traditionally used for non-food applications such as lithographic formulations, textile and paper manufacture, foundry moulding sands and explosives. Production of gum talha remains fairly constant at around 6,000 t. per year (Anderson, 1993). About 3,000 to 5,000 t. are exported annually, mainly from Sudan. Its price is about 33% that of gum arabic.
Gum talha varies considerably in its composition and functions, because of collection from different sources. This makes it unfit for any repetitive commercial process, where consistency is important. Therefore, more self-consistent, but expensive gum arabic ought to be utilised. Locations in Africa that are able to produce gum talha that is much more self consistent in composition, quality and functionality through collection from a single botanical source, and marketed as such have an opportunity to derive a new or increased income from their forest resources. The gum traders and collectors will also have to be trained for strict avoidance of admixtures of gum from different sources. These measures can help to diversify production and marketing throughout the Sahel.
Combretum nigricans occurring throughout tropical West Africa, particularly in northern Nigeria, Mali and Niger, is the major source of combretum gum. The tree is a copious gum exuder and contributes significantly to the gum production in the region. Gum combretum sells at a price of US$ 600 per t. in the international market. Such a low price leads to marketing attempts to upgrade it under false names like 'gum Niger' or 'Dark Nigerian gum arabic No. 2' or actually mixing it with gum arabic.
A major disadvantage with gum combretum is its marked tendency to 'block' in transit or in storage; the separate gum pieces filled into a jute sack convert into a solid mass which has to be broken by pick axe or sledge hammer. This is very different from behaviour of gum arabic or other gums which are not so hygroscopic. For many years, combretum gum gas commanded the lowest demand and hence price of all the exudate gums. Greater attention to locating natural production areas for top quality gum combretum of the palest possible colour, complete avoidance of dark red or fire-blackened gum, and marketing strategies aimed at keeping C. nigricans gum as a separate entity, well defined commodity available in uniform supply and constant quality, avoiding at all costs its use to adulterate gum arabic, would lead to greater demand of a larger cash flow.