Production and commercialization of gum arabic in Sudan
This paper presents details of the methods used over the years to establish the vast agroforestry resources that enabled the Sudan to supply about 85% of world's demand for gum arabic from Acacia senegal (L.) Willd.
The methods maintaining the gum gardens, tree tapping and gum collection are described. Indications of recent annual tonnages, the main uses of gum arabic, the international specifications that have to be met and trends of production are given. Exportation from Sudan is the monopoly of the gum arabic Company, which exports to its appointed agents throughout the world. Some agents simply distribute the gum as received, to their clients, but others process the gum in a range of ways necessary to satisfy the specific requirements of the commercial end-users operating in their own country, or in other countries from which they have secured a sales contract.
The gum arabic of commerce is a water-soluble exudate. The major source (95%) is Acacia senegal (hashab), with the remaining 5%, from Acacia seyal, sold as an entirely separate product (gum talha). Both tree species grow in various plant communities in the drier parts of Africa and Asia (Seif el Din 1969). Commercial use of gum arabic can be traced back to around the year 2000 bc, when the Egyptians used it in foods, adhesives, colours and paint industries. The term `gum arabic' was coined by European traders, who imported the products from Arabian ports such as Jeddah and Alexandria, and most gum traders of the time were associated with Arab countries. The trade was routed along the Nile from Sudan to Alexandria and later in 1906 to Suez on the Red Sea when the railway was constructed to link Port Sudan to Khartoum. The main ports of disembarkation were Trieste in Italy and Marseilles in France, from where the gum arabic was distributed to the rest of Europe.
Until the first two decades of the present century, Sudanese gum arabic was mainly produced in the central parts of the country, when the principal world market was Ed Dueim town on the White Nile. When in 1912, the railway was extended westwards to El Obeid, the gum arabic production was extended to Kordofan and Darfur, where the principal gum-producing trees of Acacia senegal are the dominant component of the woody vegetation on light sandy soils. Because of the remarkably good quality of the gum from these new areas, the end-users of gum arabic often requested to be supplied with `Kordofan gum'. This new terminology was applied to distinguish the gum that was purely from Acacia senegal as opposed to that from other areas, which was occasionally adulterated with exudations from other trees.
The annual gum arabic exports from the Sudan ranged from about 2000 to 7000 tons during the last two decades of the 19th century and subsequently grew to reach the maximum of 62,000 tonnes in 1968/69. During its long history, the gum trade in the Sudan witnessed some major setbacks. The first was in the period of the Mahadia wars (1881-1898), the second during World War II (1941-1945), and the third resulted from the prolonged drought in the Sahel of 1968-1975 and again from the relatively short-lived drought of 1983-1985. The last two droughts caused the exports to drop from an annual average of 45 000 t (Seif el Din 1995). From 1983 to 1991, gum production began to increase steadily back to its normal levels (fig. 1), thanks to the return of normal rainfalls in the gum belt. Despite this increase of production, exports of gum arabic are reviving at a relatively slow pace, because of the confusion caused by the short supplies for world consumption during the drought years. Similar adverse production and export situations have been faced in other gum-producing countries in Africa, such as Chad, Nigeria, Niger and Senegal. In all cases the Sudan remained the supplier of some 70-90% of world consumption of gum arabic, as indicated in table 1.
Figure 1. Exports of gum from the). The difference
between the production figures in table 2 and
these export figures probably relates to the export of gum from existing stocks in drought years. Source: Forestry National Commission.
Table 1. World gum arabic production (tonnes) 1966-1978
. Source: Seif el Din 1995
Gum arabic is one of several natural gums and one of four principal exudates that ooze from trees and harden upon exposure to air (Glicksman 1969). It has been described in various reports and laboratory analyses as forming an aqueous solution of up to 50%; colourless and free of taste and odour, these solutions do not readily interact with other chemical compounds. Because of these attributes gum arabic has been used in a wide range of industries, particularly in food preparation. For the people who tap and collect gum arabic in the producing areas, the gum is principally an export crop, with very limited use in its native areas.
Gum arabic from Sudan is obtained or tapped from A. senegal trees, from which pieces of bark 10-30 cm long and 2-4 cm broad are removed to form wounds. The gum exudes in the form of small droplets on the wounds that steadily grow in size until they become nodules of 2-5 cm diameter. These nodules are ready to be picked for sale after about 4-6 weeks.
Subsequent pickings are available at intervals of 1-2 weeks. Whereas the biosynthesis of the gum appears to be an internally controlled physiological process, the growth of the nodules seems to be more closely related to the physical environment of the tree (Seif el Din 1969). However, the exudation of gum talha from Acacia seyal trees occurs in the hot dry season, without the tree being tapped.
The main gum-producing regions of the Sudan are those falling in the Acacia senegal savanna-on-sand vegetation type, which covers most of Kordofan and Darfur states and parts of White Nile state. The clay plains of east and central Sudan contribute only about 25-30% of the total production of Sudanese gum arabic. In 1995, Kordofan produced 49.3% of the gum arabic from Sudan, Darfu 23.4%, eastern Sudan 7% and central Sudan only 0.3%.
As outlined above, the average production in the predrought years (1968-1974) was about 45,000 t an-1. This amount, however, fluctuated widely from one year to another, owing to various factors such as the rainfall, pests, the local prices of gum arabic compared with those of other crops, and the general socioeconomic stability of the gum belt (table 2). Almost all the gum produced from Sudan is destined for export, but should production exceed world demand, the excess is kept as a buffer stock that offsets deficits in years of low production. It can thus be observed that, in any one year, gum exports might be greater than current year's production and vice versa.
Table 2. Production of gum arabic during the last five seasons 1990/91-1994/95
|Export price f.o.b. Port Sudan
|1990/91||12 061||2 300|
|1991/92||7 329||2 550|
|1992/93||11 410||4 500|
|1993/94||33 458||4 000|
|1994/95||estimated 40 000||4 200|
|1995/963||estimated 30 000||* 3 500|
Source: The Gum Arabic Co. Ltd. 1995
* reduced to USD 2200 in May 1996
The uses of gum arabic are a function of its physical and chemical properties. As indicated above, it is practically colourless, tasteless, odourless and readily soluble in water, to give aqueous solutions of low viscosity. Other properties such as rheological behaviour, pH, electrolytes, ageing, compatibility and emulsifying properties have been detailed by Glicksman (1969). Chemical analyses have shown that gum arabic from A. senegal is a very complex compound containing D-glucuronic acid, D-galactose, L-arabinose, L-rhamnose and 4-0-methyl-D-glucuronic acid (Anderson 1966).
The main uses of gum arabic are in the food industries (see Hulse, this volume), particularly confectionery, which uses about 60% of world consumption. It is also used in flavourings and in pharmaceutical preparations as a building and emulsifying agent. Other industrial products that use technical grades of gum arabic include adhesives, textiles, printing, lithography, water colours, paints, paper sizing and pottery glazing.
Because of the stringent regulations imposed on all food additives, gum arabic, like all other food ingredients, is subjected to extensive toxicological research by countries, organizations and users of the produce. Most concerned in this regard are the US Food and DrugAdministration, the British Pharmacopoeia, and the FAO/WHO Joint Expert Committee on Food Additives (JECFA), all of which aim to protect the consumer of processed foods containing additives, and thus ensusre the safety of gum arabic from toxicological hazards. To achieve this end, gum arabic must conform to certain chemical specifications, and these must be adhered to, by both the producers and the processing enterprises. Among these requirements are that the gum arabic has to have a specific optical rotation of -26 to -34 degrees and nitrogen content of 0.24-0.41% (Anderson et al. 1990, 1991). These characteristics and a whole list of other specifications are met only by gum arabic from A. senegal (L.) Willd. var. senegal (Brenan 1983) and not by gum talha from Acacia seyal.
Commercial gum arabic is the product of A. senegal var. senegal, which is widely distributed on the African continent as well as in Arabia, Pakistan and India (Brenan 1983). Three other varieties of A. senegal are recognized-var. kerensis, which seems to be restricted in its distribution to the East African countries of Ethiopia, Somalia, Uganda, Kenya and Tanzania, and var. leiorhachis and var. rostrata, both of which seem to be restricted to eastern and southern Africa. It is reported that gum exudates from these three varieties are distinctively different from the true gum arabic of var. senegal. Because of the strict safety regulations against toxicity, gum talha from A. seyal is no longer acceptable, as it does not conform to the agreed specifications.
A. senegal var. senegal is the only variety that is being cultivated for gum production in the Sudan, as well as in some other Sahelian countries. It is incorporated in the famous agroforestry system known as the bush-fallow system of shifting cultivation, described by Seif el Din (1981). In this system the gum trees are encouraged to grow on the abandoned farm plots during the fallow period, during which they improve soil fertility, so ensuring adequate crop production when cultivation is resumed. The tree, which protects the soil from erosion and improves its fertility, also provides the farmer with gum as a cash crop during the dry season. This system ensures optimum and sustainable utilization of the natural resources, since both the gum production and the crop cultivation form productive components of the system. Added to this is the fact that animals graze under the gum trees during the dry season without harming the trees. When the trees are felled to allow cultivation, the wood is used for fuel, for building materials and for building fences around farm plots.
This agroforestry system has, however, undergone substantial deterioration, particularly in the main gum-producing areas in Kordofan and Darfur, as a result of the recurring droughts. Tree mortality was widespread, and especially severe in the northern parts of those regions, resulting in partial or total collapse of the bush fallow system. In view of this, the government has started a project, assisted by the United Nations Sudano-Sahelian Office, to restock the gum belt in Kordofan and Darfur. In this project farmers are provided with seeds and seedlings to plant in their own fields. Similar activities are also being carried out elsewhere in the gum belt, spearheaded by the Forest Extension Unit of the Forest National Corporation (FNC).
Because of the importance of gum arabic for the economy of Sudan, the forest service has adopted a strategy of establishing plantations of Acacia senegal inside forest reserves to act as buffer plantations. There are at present about 30 000 feddans (12 500 ha) in Blue Nile, Kassala and Kordofan regions, and these are annually rented out to gum tappers on a share-cropping basis. Furthermore, gum plantations constitute a considerable part (30-40%) of the FNC annual tree-planting programme. The Sudanese government also decreed that all the mechanized farming schemes should plant trees on 10-15% of their area to act as shelterbelts, using Acacia senegal var. senegal as the main species.
In Sudan, gum buyers do not have contacts with the growers, farmers, tappers or collectors but buy competitively at auction. The farmgate price is fixed by the Sudanese government each October to induce villagers and others to go out to tap the trees and thereafter collect the gum. In years in which there is a surplus and `buffer stocks' accumulate, the farmgate price is lowered to discourage maximum production. In years of shortage, the opposite applies. The Sudanese merchants licensed to buy at auction must, by law, pay the grower, farmer, tapper or collector immediately after the auction. The minimum price that can be paid at auction is the farmgate price, i.e., the official base price. Gum arabic that, for any reason, is not bought by an independent licensed buyer must be bought by the official Gum Arabic Company at the official base price.
After the merchants buy at auction, they have the gum cleaned and graded by hand in their sheds by young female employees. The grades used are:
Hand-Picked Selected (HPS)
Cleaned and Sifted (CAS)
These grades are then delivered to Port Sudan and sold to the Gum Arabic Company at prices fixed for each grade to allow the buyer, cleaner and grader a margin of profit after the costs of transportation have been met. A 40% export tax is levied by the government when the gum is loaded on to a vessel at Port Sudan for export. The sole permitted exporter, the Gum Arabic Company, ships worldwide to its official appointed agents (one per country), who get 1.5% of the selling price as a discount or commission. A further 0.5% is retained by the Gum Arabic Company to finance research and promotional activities. The agents do not normally hold stocks of gum; they simply arrange contracts for the gum to be delivered from Port Sudan direct to an end-user.
In recent years there has been a growing belief that the present monopolistic exportation by the Gum Arabic Company, introduced in 1967-1968, should be deregulated so that any Sudanese person could buy direct from the farmer or collector and then export the gum to any end-user in any country. This view is becoming more strongly held because the present system, intended to ensure the quality of Sudanese production, is being abused by the active smuggling of gum to Chad, Nigeria, Ethiopia, Uganda, Kenya and other countries to avoid the 40% export tax.
Gum arabic produced by countries other than Sudan is cheaper but generally of lower quality, because the cleaning and grading are not as effectively and strictly regulated, because gums from any botanical species may be intermixed in a very variable way, and because other countries have no planted stands of Acacia senegal var. senegal such as those forming the basis of Sudanese gum arabic production, as a result of the extensive agroforestry developments over many years.
Warm Seas Ltd. is an international multibusiness company involved in the gum trade. There are five divisions, including marketing, consulting, and international trading. Throughout its history, Warm Seas has served over 450 multinational companies. The group employs about 350 staff worldwide and has offices and affiliates in 25 countries around the world. Its main offices are in Sudan, the UK, the USA, France, Germany and the UAE.
Warm Seas has been operating successfully for over 20 years, using London as its headquarters. It has developed a strong business in Africa and the Middle East. The group now operates in Africa, Europe, the USA and Asia. Warm Seas through its quality service has built excellent relationships with some of the major food and beverage companies in the world. Warm Seas has equipped its food processing plant in Europe with the latest technology in food processing and continues to deliver total quality service to its customers around the world.
Gum arabic has remained an important cash crop for Sudanese peasants in the arid and semi-arid areas over thousands of years. Its production is going to remain, for a long time to come, a peasant industry for millions of smallholders in areas where other income-generating activities are not available. The gum tree itself is essential in sustaining the farming system, and thus, whether it produces gum arabic or not, farmers will encourage its growth on their lands. This undoubtedly will ensure sustainability of gum supplies to the world market. Sudan, in this respect, has the advantage that the gum tree Acacia senegal var. senegal occurs naturally over the large area known as the Gum Belt, which covers 40-50% of the total area of the country.
Because the tree grows in almost pure stands of natural bush and groves of pure gum gardens, Sudan will continue to offer on the world market the highest grade of gum arabic with the required specifications. Other countries that could do the same are those in the Sudano-Sahelian zone of Africa such as Chad, Nigeria, Mali and Senegal.
Anderson D.M.W., Hirst Sir Edmond & Stoddart J.F. 1966. Some structural features of Acacia senegal gum (gum arabic). Journal of the Chemical Society Section C, p 1959-1966.
Anderson D.M.W., Brown D.D.M., Morrison N.A. & Wang W. 1990. Specifications for gum arabic (Acacia senegal) analytical data for samples collected between 1904 and 1989. Food Additives and Contaminants 7(3):303-321.
Anderson D.M.W., Millar J.R.A. & Wang W. 1991. Gum arabic (Acacia senegal): unambiguous identification by 13C-NMR spectography as an adjunct to the Revised JECFA Specification and the application of 13C-NMR spectra for regulatory legislative purposes. Food Additives and Contaminants 8(4):405-421.
Brenan J.P.M. 1983. Present taxonomy of four species of Acacia (A. albida, A. senegal, A. nilotica, and A. tortilis). In: Manual on taxonomy of Acacia species. FAO, Rome.
Glicksman M. 1969. Gum technology in the food industry. Academic Press, New York and London. p 97-110.
Gum Arabic Co. Ltd. 1995. Gum arabic in the Sudan. Workshop on Gum Arabic, 2-3 October 1995, El Obeid, Sudan.
Seif el Din A.G. 1969. The natural regeneration of Acacia senegal (L.) Willd. MSc thesis, University of Khartoum, Sudan.
Seif el Din A.G. 1981. Agroforestry practices in the dry regions. p 419-434. In: Proceedings of Kenya National Seminar on Agroforestry, ed. L. Buck, P. Huxley, F. Owino & D. Ngugi. ICRAF and University of Nairobi, Nairobi, Kenya.
Seif el Din A.G. 1995. Gum arabic production in the Sudan. Agricultural Insurance Workshop in the Sudan, Sheikan Insurance and Reinsurance Co. Ltd. Khartoum, Sudan.