Make your own free website on Tripod.com
ALNICOLSA PRODUCTOS AGROINDUSTRIALES

VENTANILLA - CALLAO (PERÚ)
Telefax.511. 553.0981.  E-mail. lebr7@yahoo.com

lebr7@yahoo.com

Página principal
• 
Indice de productos
• Venta de productos
• 
Páginas peruanas
• Venta de Maquinarias
• 
Programas Gratis
• Más Monografias
• 
ENLACES

Bienvenid@s a La Página Virtual de ALNICOLSA del Perú S.A.C.  Telf: 5530981 - Ultima Actualización

GUMS, RESINS AND LATEXES

INTRODUCTION

Apart from essential oils, which provide an array of flavours and fragrances, gums, resins and latexes are perhaps the most widely used and traded category of non-wood forest products other than items consumed directly as foods, fodders and medicines. A recent estimate put the value of the world market for gums used as food additives at about US$ 10 billion in 1993, of which the two largest "forest" gums (gum arabic and locust bean) accounted for just over 12%; the remainder were mainly the seaweed gums, starches, gelatin and pectin (NAUDE, 1994). This takes no account of non-food uses of gums.

Some idea of the quantities of natural gums and resins which enter international trade can be gained by examining trade statistics. Imports into the European Community of "natural gums, resins, gum-resins and balsams", excluding gum arabic, are given in Table 2 for the period 1988?93. Annual imports averaged approximately 20 000 tonnes. Inclusion of gum arabic (Table 6) adds a further 28 000 tonnes to this figure.

Indonesia, India and the People's Republic of China are among the world's biggest producers of gums and resins, and exports from these countries are shown in Tables 3, 4 and 5, respectively. Note that some of the figures in Table 3 (and Table 2, Brazil) are distorted by the inclusion of pine resin/. Sudan (Table 12) and Indonesia are the world's two biggest exporters of natural gums and resins.

The uses of the gums discussed in this report are elaborated in the sections concerned, but they embrace food, pharmaceutical and miscellaneous technical applications. In the food industry, advantage is taken of their thickening, stabilizing, emulsifying and suspending properties and they are employed in a very wide range of products, both foods and drinks. In the pharmaceutical industry they are used as binding agents in tablets and as suspending and emulsifying agents in creams and lotions; some have specific applications in the dental and medical fields. Miscellaneous end users include the printing and textile industries.

Resins, including oleoresins and balsams, have an equally diverse range of applications, although the volumes which are traded have declined considerably (with the exception of pine resin) over the last 50 years.

Their use in paints, varnishes and lacquers, in particular, has suffered as cheaper, synthetic alternatives have become available. Some resins, however, are still used in this way. Others, especially the soft resins and balsams, are used as sources of fragrances and pharmaceuticals, usually after preparation of a suitable solvent extract or distillation of a volatile oil.

The decline in use of certain types of natural product at the expense of synthetics, referred to above in the case of resins, has been even greater for most of the latexes discussed in this report. In their heyday in the early part of the century, they were produced in large volumes to meet the needs of the growing chewing gum industry and for use in specialized applications such as insulating materials and the manufacture of golf balls. Today, their use is but a fraction of what it was.

The decline in use of many gums, resins and latexes is a reflection of industry's general preference for raw materials which are of consistent, predictable quality, which are not subject to the vagaries of weather, insect pests and economic and political stability in producing countries, and which are available at an attractive price. In many cases, the synthetic alternatives which meet these needs are also technically superior to the natural products they replace. Notwithstanding these remarks, however, some natural gums and resins do enjoy continued use - gum arabic is a prime example - either because they have functional properties which synthetics cannot match or because they are available at a price which makes it cost-effective to continue to use them. In food use, particularly, any change of formulation requires a change in the labelling of the end product, which is very costly to the manufacturer and not something which is done without very good reason. (Equally, if a switch is made away from using a natural gum then that market cannot easily be regained at a later date). There are also some marketing advantages for manufacturers in being able to label their products as containing natural, rather then synthetic, additives.

The above remarks apply, essentially, to the large-scale consumer markets and take no account of the use of gums, resins and latexes at the local level, by the communities which collect them. This use is not easily quantified but is clearly very important. Some of the resins are used for making torches and for caulking boats and baskets, or as sources of incense. Many are used for medicinal purposes.

The permitted use of gums in foods is a subject of some concern and much legislation. Recent changes in the toxicological status of gums, including the exudate and seed gums discussed in this report, have been summarized by ANDERSON (1991). Present and future European legislation on food hydrocolloids (gums) has been summarized by GRAY and PENNING (1992). Where applicable, specifications for gums (and resins) used in foods and dealt with in this report have been included in the selected bibliography at the end of each section. However, any prospective new producer or exporter of gums intended for food use should consult either their national standards organization (for information on local quality requirements) or international organizations or importers (for up-to-date advice on requirements in end-user countries).

OPPORTUNITIES FOR DEVELOPMENT OF NEW OR IMPROVED SOURCES OF GUMS, RESINS AND LATEXES

ROBBINS (1988) has stated, "in spite of the problems which have beset the gums market in recent years, the fact remains that in many cases the gums provide a valuable source of income for many poor smallholders or itinerant labourers, either in very poor countries or in the poorest regions of rather more developed countries. As such they are important commodities ...". This remains true today. Tens of thousands of people worldwide, living in regions ranging from semi-arid lands to moist rainforest, depend on the collection of gums, resins and latexes as a means of cash income. Equally, many millions of people in consuming countries make use of these products in their everyday life.

Markets for many of the products have undoubtedly declined over the years and, for some, these markets will never be recovered. This is especially true for some of the latexes. However, for others, there will continue to be a demand, and provided quality and price are right (and, in the case of food gums or resins, legislation continues to permit them) the end-user industries in the consuming countries will wish to continue using them.

The need to maintain quality or, better still, improve it, in order to retain or increase markets cannot be over-emphasized. The quality of the consignment of gum or resin received by an importer depends on a number of factors:

Every effort should therefore be made to improve the collection and post-harvest handling of gums and resins. The use of improved methods of tapping will have the added incentives of increasing yields and minimizing or eliminating damage to the forest resource. Quality control measures should be in place which ensure that there is no mixing of gums from different botanical sources, either accidentally or deliberately by the collector or trader. And excessive handling should be avoided which increases the risk of contamination, including microbial contamination.

In the past especially, but to some extent even now, the wild sources of gums, resins and latexes have been damaged by the methods employed for tapping and by over-exploitation of the resource. The introduction of better tapping techniques is one way of avoiding damage, but the use of cultivated sources can also reduce the pressure on the natural forest, and by improving the accessibility of the trees to the collector can increase the efficiency of collection. Cultivation may be on a large scale (as, for example, with some of the plantations of Acacia senegal in Sudan which are tapped for gum arabic) or in an agroforestry context (as in the case of Shorea javanica in Indonesia which is being grown as a source of damar). Some species of Canarium have the potential for multipurpose use as a source of edible fruits or nuts and elemi resin.

There are good grounds for optimism that despite the changes which have occurred in the markets over the years there will continue to be a demand for gums, resins and latexes (albeit more for some than others) and that there are opportunities for people in the producing countries, providing due attention is given to such aspects as quality control of the product and sustainable management of the resource.
 

COVERAGE AND FORMAT OF THE REPORT

Many thousands of plant species yield gums, resins or latexes, and probably several hundreds are utilized to produce items of trade, either local or international. Of these, the 22 listed in Table 1 are the subject of this report.

All except one enter world trade, and those which do range from large volume gums such as gum arabic - where over 30 000 tonnes were exported from producer countries in 1994 - to small volume resins and latexes, where less than 50 tonnes/year are traded. Mesquite seed gum is not yet produced commercially but has the potential to do so.

Except for tragacanth and asafoetida/galbanum, which come from small shrubby plants, all the products are obtained from trees, although these vary in size from relatively small Acacia to Dyera species up to 50 m or more tall. They have been chosen to illustrate the diversity of the products and their applications, and the different types of forest cover, ecological zones and geographical regions from which they come ? from food additives, flavours and fragrances to pharmaceuticals and industrial applications; from small shrubs or trees of the arid and semi-arid zones of Africa and India to medium-sized trees of the Mediterranean region, and large trees of the Amazonian and Southeast Asian rainforests. The developmental potential of the products discussed ranges from those with high potential such as gum arabic, locust bean and damar to those with very little potential such as dragon's blood and balata.

A standard format has been adopted when discussing each product:

A large number of gums, resins and latexes have inevitably had to be omitted from this report, including some which are traded internationally in significant quantities. A few have been omitted because they have already been the subject of recent publications:


Some have been omitted because they are not forest products. These include (a) seaweed gums, (b) those produced as agricultural crops and (c) some produced commercially by microbial biosynthesis:

(a) Agar
Alginates
Carrageenan

(b) Guar gum from Cyamopsis tetragonoloba
Psyllium gum from Plantago spp.
Guayule latex from Parthenium argentatum
Rubber latex from Hevea brasiliensis

(c) Gellan gum
Xanthan gum

Processed gums such as modified starches and celluloses are excluded. Others have been omitted in order to keep the present report to a reasonable size or because there is insufficient published information to enable an adequate account to be given of the particular gum, resin or latex. These include:

Gums
Cashew from Anacardium occidentale
Ghatti from Anogeissus latifolia
Gum arabic-like gums from Combretum, Albizia and
Leucaena spp.
Gum from Cassia spp. (e.g., C. tora)
Gum from Sesbania spp. (e.g., S. bispinosa)
Semla from Bauhinia retusa
Tamarind from Tamarindus indica

Resins
Accroides from Xanthorrhoea spp.
Gaharu resin-soaked wood from Aquilaria spp.
Gamboge from Garcinia spp.
Guaiacum from Guaiacum spp.
Gumweed from Grindelia camporum
Gurjun balsam from Dipterocarpus kerrii
Kauri from Agathis
Labdanum from Cistus spp.
Lac (shellac) from the lac insect
Sandarac from Tetraclinis and Callitris spp.

Latexes

Chilte from Cnidoscolus spp.

Many other gums, resins and latexes have been the subject of research reports but these are not discussed further here.

REFERENCES

ANDERSON, D.M.W. (1991) Recent changes in toxicological status of permitted food emulsifiers, stabilisers and thickeners. South African Journal of Food Science and Nutrition, 3(2), 25?28.

COPPEN, J.J.W. and HONE, G.A. (1995) Gum Naval Stores: Turpentine and Rosin from Pine Resin. Non-Wood Forest Products series. No. 2. 62 pp. Rome: Food and Agriculture Organization.

GRAY, P.S. and PENNING, W. (1992) Present and future legislation of food hydrocolloids. pp 17?27. In Gums and Stabilisers for the Food Industry, Vol. 6. Proceedings of 6th International Conference, Wrexham, 1992. Oxford: IRL Press.

NAUDE, A. (1994) Food additives '94. Thickeners, the next generation. Chemical Marketing Reporter (27 June), pp SR16 and SR18.

ROBBINS, S.R.J. (1988) Gum arabic. pp 18?33. In A Review of Recent Trends in Selected Markets for Water-Soluble Gums. ODNRI Bulletin No. 2. 108 pp. London: Overseas Development Natural Resources Institute [now Natural Resources Institute, Chatham].
 
 

Table 1. Gums, resins and latexes described in the report
 
 
Gum, resin or latex  Main genera  Family  Main producing regions 
Exudate gums 
Gum arabic  Acacia  Leguminosae  Africa 
Karaya  Sterculia  Sterculiaceae  Asia, Africa 
Tragacanth  Astragalus  Leguminosae  Asia Minor 
Seed gums 
Locust bean  Ceratonia  Leguminosae  Mediterranean 
Mesquite  Prosopis  Leguminosae  Americas, 
Africa, Asia 
Tara  Caesalpinia  Leguminosae  S America 
Hard resins 
Copal  Agathis  Araucariaceae  SE Asia 
Damar  Shorea ,
Hopea, Vatica
Dipterocarp- aceae  SE Asia 
Mastic  Pistacia  Anacardiaceae  Mediterranean 
Dragon's blood  Daemonorops  Palmaceae  SE Asia 
Soft resins/balsams 
Benzoin  Styrax  Styracaceae  SE Asia 
Styrax  Liquidambar  Hamamelidaceae  Asia Minor, 
C America 
Peru/Tolubalsams  Myroxylon  Leguminosae  C/S America 
Copaiba  Copaifera  Leguminosae  S America 
Elemi  Canarium  Burseraceae  SE Asia 
Asafoetida/ 
Galbanum 
Ferula  Umbelliferae  Asia Minor 
Latexes 
Chicle  Manilkara  Sapotaceae  Americas 
Jelutong  Dyera  Apocynaceae  SE Asia 
Sorva  Couma  Apocynaceae  S America 
Gutta percha  Palaquium  Sapotaceae  SE Asia 
Balata  Manilkara  Sapotaceae  S America 
Maçaranduba  Manilkara  Sapotaceae  S America 

 
 

Table 2. Gums and resinsa (excluding gum arabic): imports into the European Community, and sources, 1988-93
(tonnes)
 
 
1988 
1989 
1990 
1991 
1992 
1993 
Total 
15754 
21238 
22774 
25161 
22718 
13521 
Of which from 
Brazil 
1056 
3959 
8197 
10041 
7431 
1427 
Indonesia 
2599 
3033 
2680 
2567 
3609 
3239 
India 
1694 
2108 
690 
796 
1111 
1352 
Senegal 
1182 
1735 
1824 
1477 
1329 
919 
Iran 
956 
969 
779 
910 
689 
808 
Singapore 
863 
737 
1186 
813 
855 
630 
Germany 
827 
683 
711 
649 
912 
801 
France 
561 
797 
894 
1041 
676 
614 
UK 
409 
504 
694 
527 
676 
522 
China,P.Rep. Of 
285 
457 
202 
2010 
1871 
33 
Nigeria 
359 
698 
503 
294 
201 
381 
Philippines 
207 
259 
515 
143 
177 
291 
Mali 
104 
446 
549 
560 
484 
197 
Sudan 
343 
318 
234 
433 
317 
279 
Spain 
197 
227 
391 
320 
438 
101 
Portugal 
463 
122
143 
548 
59 
88 
Ethiopia 
220 
231 
285 
139 
131 
62 
Somalia 
108 
167 
121 
151 
237 
202 
South Africa 
1288 
1478 
363 
Netherlands 
283 
262 
87 
226 
307 
267 
USA 
232 
271 
331 
186 
114 
115 
Australia 
101 
111 
152 
186 
134 
209 
Turkey 
114 
242 
55 
33 
25 
Albania 
18 
185 
257 
72 
277 
Others 
1285 
1239 
1188 
854 
862 
694 

Source: Eurostat
Note:
a "Natural gums, resins, gum-resins and balsams".
b A significant proportion of Brazilian exports is believed to be crude pine
resin imported into Portugal.
 
 

Table 3. Gums, resins and latexesa: exports from Indonesia, by type, 1988-93
(tonnes; US$ millions)
 
 
 
1988 
1989 
1990 
1991 
1992 
1993 
Total 
17114 
33236 
40531 
41270 
35052 
41961 
FOB value 
9.8 
19.6 
24.8 
23.4 
22.1 
24.9 
Of which :
Damarb
10343 
11372 
10878 
12573 
10175 
13285 
Jelutongc
2358 
5373 
6495 
3700
2712 
1182 
Copal 
2485 
1811 
1766 
1880 
1863 
1886 
Gum arabicd
2937 
2050 
2405 
1988 
361 
Benzoine
1157 
975 
884 
1126 
806 
824 
Lac 
411 
227 
703 
221 
245 
311 
Gutta percha 
75 
156 
316 
366 
241 
Dragon's blood 
26 
59 
71 
87 
47 
25 
Gahuru 
39 
44 
47 
181 
204 
"Other gum"f
107 
9947 
16557 
18602 
16454 
23255 
"Other resin" 
129 
391 
927 
311 
177 
387 
Others 
95 
30 
38 

Source: National statistics

Notes:

a Excludes agar-agar (a seaweed gum) and "Resin pine"
(= pine rosin, a processed product of crude pine resin).

b Includes "Damar", "Resin batu" and "Resin mata kucing" (see section on DAMAR).

c Includes raw, pressed, refined, and other.

d Very improbable that this is genuine gum arabic.

e Classified as "Frankincense" (see footnote to Table 23).

f From 1989, it is probable that a large proportion of this is crude pine resin.
 

Table 4. Gums and resins: exports from India, by type, 1987/88-1993/94a
(tonnes)
 
 
87/88 
88/89 
89/90 
90/91 
91/92 
92/93 
93/94 
Total 
8013 
9674 
7818 
8257 
7299 
7124 
8513 
Of which :
Lacb
5038 
7157 
5169 
6958 
5673 
4989 
5935 
Karaya 
2001 
1831 
1628 
599 
574 
843 
1443 
Asafoetida 
140 
144 
149 
130 
164 
231 
205 
Olibanum 
167 
81 
19 
75 
70 
113 
66 
Gum arabic 
30 
30 
80 
83 
Asian gum 
23 
41 
37 
12 
19 
"Other natural gums" 
484 
331 
683 
374 
567 
660 
592 
"Other gum resins" 
102 
42 
61 
51 
214 
97 
116 
"Other resins" 
21 
30 
66 
18 
87 
45 
Others 
31 
14 
18 

Source: National statistics

Notes: a Year runs April-March

b Includes shellac, seedlac, button and garnet lac, stick lac,
dewaxed and decolourised lac, bleached lac, and other lacs including
lac dye.
 
 

Table 5. Gums and resinsa: exports from the People's Republic of China, and destinations, 1990-92
(tonnes)
 
 
 
1990 
1991 
1992 
Total 
8701 
340 
2755 
Of wich to: 
Hong Kong 
6575 
212 
1497 
India 
2105 
Spain 
350 
Viet Nam 
305 
Indonesia 
29 
55 
Thailand 
15 
52 
Singapore 
59 
Nigeria 
72 
Russia 
50 
USA 
12 
12 
Japan 
22 
Iran 
14 

Source: China's Customs Statistics Yearbook
Note: a "Natural gums, resins, and balsams excluding lac and gum arabic"

___________________________________
2/ Annual world production of pine resin is almost one million tonnes, making it by far the most important natural resin of commerce. It is obtained by tapping pine trees and is used as a source of turpentine and rosin, but it has been reviewed in detail elsewhere (COPPEN and HONE, 1995) and is not discussed in this report.

 


2

EXUDATE GUMS

GUM ARABIC, GUM TALHA AND OTHER ACACIA GUMS


DEFINITION

The term gum arabic is used with varying degrees of precision by different groups of people. In the context of its use as a food additive the most recent international specification, published by FAO (FAO, 1990), defines gum arabic as the "dried exudation obtained from the stems and branches of Acacia senegal (L) Willdenow or closely related species". The specification then proceeds to give limits for certain parameters which have been selected to try and ensure that only gum from A. senegal (and closely related species) satisfies the specification (see Quality and prices below). The need for such legislation arises from the need to assure the public on safety grounds that there are no hazards associated with ingestion of gum arabic; gum arabic which complies with the definition and specifications has been tested and shown to be safe to consume./

In Sudan, the term gum arabic is used in a wider context to include two types of gum which are produced and marketed, but which are, nevertheless, clearly separated in both national statistics and trade: "hashab" (from A. senegal) and "talha" (from A. seyal). In a still wider sense, gum arabic is often taken to mean the gum from any Acacia species (and is sometimes referred to as "Acacia gum"). "Gum arabic" from Zimbabwe, for example, is derived from A. karroo.

In practice, therefore, and although most internationally traded gum arabic comes from A. senegal, the term "gum arabic" cannot be taken as implying a particular botanical source. In a few cases, so-called gum arabic may not even have been collected from Acacia species, but may originate from Combretum, Albizia or some other genus. In the discussion which follows, the term "gum arabic" will generally be used in the generic sense as any Acacia gum unless it is qualified by some other statement or the botanical source is specified.

Statistical data originating in Sudan and shown in Tables 11a, 11b and 12 separate gum hashab and gum talha. Figures relating to Sudan in other statistical tables (Tables 6, 7, 9 and 10) are assumed to combine both types of gum arabic (hashab and talha).

DESCRIPTION AND USES


Gum arabic from A. senegal is a pale to orange-brown coloured solid, which breaks with a glassy fracture. The best grades are in the form of whole, round tears, orange-brown in colour and with a matt surface texture; in the broken, kibbled state the pieces are much paler and have a glassy appearance (see section on quality below). Inferior grades, and gum from species other than A. senegal, may not have the characteristic tear shape and are often darker in colour. Gum from A. seyal (gum talha) is more friable than the hard tears produced by A. senegal and is rarely found as whole lumps in export consignments.

The gum arabic-yielding Acacias grow in semi-arid areas and the vast majority of gum arabic which enters international trade originates in the so-called gum belt of Sub-Saharan Africa, extending from the northern parts of West Africa eastwards to Sudan and Ethiopia. A little gum is of Indian origin.

Gum arabic is a complex, slightly acidic polysaccharide. The precise chemical and molecular structure differs according to the botanical origin of the gum, and these differences are reflected in some of the analytical properties of the gum. As a result, the functional properties and uses to which gum arabic can be put (and its commercial value) are also very dependent on its origin.

Unlike some other gums such as tragacanth, locust bean and the seaweed gums, gum arabic is very soluble in water and forms solutions over a wide range of concentrations without becoming highly viscous. The combination of high solubility in water and low viscosity confers on gum arabic its highly valued emulsifying, stabilizing, thickening and suspending properties. Despite some substitution of gum arabic by cheaper alternatives, brought about in the past by shortages of supply and high prices, it has remained the most important of the exudate gums and in some applications it has technical advantages which make it difficult to substitute completely. Its uses fall into three main areas: food, pharmaceutical and technical.

Food use

As noted earlier, the FAO specification for gum arabic intended for food use stipulates that it should come from A. senegal or closely related species. Even apart from legislative requirements, the quality and technical performance of gum arabic from this source makes it the material of choice in most cases. In Europe, the food additive number of gum arabic is E414.

Confectionery remains a major use for gum arabic, although supply and price pressures have led to a marked reduction in the amount of gum arabic used in some traditional items such as "fruit gums" and pastilles. The role of gum arabic in confectionery products is usually either to prevent crystallization of sugar or to act as an emulsifier. In candy products it is also used as a glaze.

It finds wide application as a means of encapsulating flavours (for example, spray-dried flavours and citrus oils) and is also used in a range of dairy and bakery products (especially as a glaze or topping in the latter). It is used in soft and alcoholic drinks, either as a vehicle for flavouring or as a stabilizer or clouding agent.

Pharmaceutical use

Gum arabic's use in pharmaceuticals is much less than it once was, and it has been displaced in many of its applications by modified starches and celluloses. However, it still finds some use in tablet manufacture, where it functions as a binding agent or as a coating prior to sugar coating, and it is also used as a suspending and emulsifying agent, sometimes in combination with other gums.

Technical and miscellaneous uses

An important non-food/pharmaceutical application of gum arabic is in the printing industry, where it is used to treat offset lithographic plates: as a protective coating to prevent oxidation;

as a component of solutions to increase hydrophilicity and impart ink repellency to the plates; and as a base for photosensitive chemicals.

Other technical uses include ceramics, where gum arabic helps to strengthen the clay, certain types of inks, and pyrotechnics. Use in textiles, paints and adhesives (including the traditional office glue and postage stamps) has decreased to very low levels in recent years, at least in Western markets.

WORLD SUPPLY AND DEMAND TRENDS

Markets

The use of gum arabic has a very long history but in modern times production and trade has been dominated by Sudan. Levels of supply from Sudan are therefore a good indicator of consumption.

A more detailed discussion of production levels in Sudan is given below, but towards the end of the 1960s total gum arabic production (hashab + talha) was in excess of 60 000 tonnes/year; supplies of gum arabic from other countries meant that total world usage was around 70 000 tonnes. Events in the 1970s and 1980s led to fluctuations in both the supply and price of gum arabic and, as a consequence, to changes in demand. The severe Sahelian drought of 1973/74 resulted in a world shortage of gum arabic and high prices which, in turn, accelerated the replacement of gum arabic by substitutes such as modified starches. A low point of approximately 20 000 tonnes of Sudanese exports was reached in 1975, which recovered to around 40 000 tonnes during 1979. A further drought in 1982?84, combined with political and civil unrest, saw levels of exports fall to below 20 000 tonnes in some years in the mid?/late 1980s and early 1990s.

Demand for gum arabic has therefore been constrained at times by the supply, and under these circumstances end-users who switch to alternatives do not always revert to gum arabic when supply problems are eased. It is unlikely, therefore, that world markets for gum arabic will reach the heights that they once did, although the superior properties of gum arabic (especially good quality material from A. senegal) will ensure that it retains substantial markets if availability is assured and prices are favourable.

The European Community is by far the biggest regional market for gum arabic and imports into it, with sources, are given in Table 6 for the period 1988?93. Imports averaged almost 28 000 tonnes/year over the six years, with a peak of over 32 000 tonnes in 1991.

A breakdown into destinations of imports within the EC is given in Tables 7 and 8 for Sudanese and Nigerian gum arabic, respectively. France and the United Kingdom are the biggest markets (although they both re-export a large proportion of their imports) followed by Italy and Germany. The United Kingdom has been a consistent buyer of Nigerian gum, although France and Germany have imported large quantities in recent years. France is the main importer of gum arabic from the Francophone countries of West and Central Africa.

Outside the EC, the United States is the largest market for gum arabic. Imports for 1991?94, and their sources, are given in Table 9; they averaged 7 500 tonnes annually but exceeded 10 000 tonnes in 1994.

Japanese imports averaged 1 900 tonnes/year during 1988?94; year-by-year details are shown in Table 10.

Supply sources

The gum belt referred to earlier occurs as a broad band across Sub-Saharan Africa, from Mauritania, Senegal and Mali in the west, through Burkina Faso, Niger, northern parts of Nigeria and Chad to Sudan, Eritrea, Ethiopia and Somalia in the east, and northern parts of Uganda and Kenya. Most of these countries appear in the trade statistics as sources of gum arabic, although they differ greatly in terms of the quantities which are involved.

Sudan is the world's biggest producer of gum arabic, and since very little is consumed domestically it is also the main source of gum in international trade. Sudanese production data are given in Tables 11a and 11b: 5?year annual averages since 1960 are given in Table 11a and yearly figures for the crop years 1988?94 are shown in Table 11b. In both cases, gum hashab is distinguished from gum talha.

The data in Table 11a show a drop in production by more than half in the last decade compared to that in the 1960s (when it averaged about 48 500 tonnes/year). In the ten years 1950?59 (not shown) production averaged just under 41 000 tonnes/year. The more detailed data in Table 11b show an all-time low of 7 600 tonnes in 1992. Since then, production has increased and it is expected to be the highest for some years in 1995.

The proportion of gum talha in Sudanese production of gum arabic (Tables 11a and 11b) is usually around 5?15%. However, in recent years (Table 11b) it has varied from less than 200 tonnes (3%) in 1992 to over 11 000 tonnes (33%) in 1994.

Exports from Sudan averaged 20 300 tonnes/year in the period 1988?94 (Table 12). Comparison with production data is difficult because of the uncertainty in the level of carry-over of stocks from one year to the next.

Nigeria is the second biggest producer and exporter of gum arabic after Sudan. Direct imports into the European Community from Nigeria averaged 4 500 tonnes/year during 1988?93 (Table 6). Import data for the United States (Table 9) show that Nigeria was the second biggest primary source of gum arabic.

Of the other producers, Chad is the next most important after Sudan and Nigeria; direct imports into the EC for 1988?93 averaged 2 000 tonnes/year (Table 6). However, a significant proportion of the gum exported from Chad, as well as from the Central African Republic, is believed to originate in Sudan and enter the neighbouring countries through illegal cross-border trade. Likewise, some gum from Cameroon originates in Chad. The 1 000 tonnes of gum arabic imported into the EC from the former Soviet Union in 1988 represents re-exports of bartered gum from Sudan.

A few countries which have gum-yielding Acacias produce gum for the local market, but not in sufficient quantities to enable exports to be made. Two such examples are Zimbabwe and South Africa, which produce gum arabic from A. karroo.

Outside Africa, India produces small amounts of gum, similar in quality to gum talha, but a proportion of her exports of gum arabic consists either of re-exports of African gum or locally produced gum ghatti (from Anogeissus latifolia) misclassified as gum arabic.

Quality and prices

The quality of gum arabic as received by the importer is very dependent on the source. Gum arabic (hashab) from Sudan is the highest quality and sets the standard by which other "gum arabics" are judged. Not only does Sudanese gum come from a species (A. senegal) which intrinsically produces a high quality exudate with superior technical performance, but the collection, cleaning, sorting and handling of it up to the point of export is well organized and highly efficient (see COLLECTION/PRIMARY PROCESSING). Within Sudan, gum arabic from the Kordofan region has the highest reputation, and traders and end-users in importing countries often refer to "Kordofan gum" when indicating their preferences.

Nigerian gum arabic, on the other hand, has a reputation for very variable quality. Some gum is comparable to the best Sudanese quality but much of it is poorer. A major problem for importers and end-users is the inconsistent, and often heterogeneous, nature of the consignments: gum of varying degrees of cleanliness and colour is present, which reflects the less rigorous methods of harvesting and post-harvest treatment practised in Nigeria compared with Sudan. One aspect, in particular, which adversely affects the quality is the mixing of different types of gum, i.e., gum collected from different species of Acacia.

Gum talha from Sudan (produced from A. seyal) is intrinsically a poorer quality gum than hashab ? it has inferior emulsifying properties and even light-coloured samples of whole gum sometimes form dark solutions in water due to the presence of tannins and other impurities. It is more friable than hashab.

Quality criteria

As noted earlier, an FAO (JECFA) specification exists for gum arabic intended for use as a food additive; in the United States, a Food Chemicals Codex specification exists. For pharmaceutical use, gum arabic appears in many pharmacopoeias, including the British Pharmacopoeia.

The JECFA specification has undergone a number of revisions over the years. The present one (published in 1990) specifies limits on such things as loss on drying, ash, acid-insoluble matter, arsenic, lead and heavy metals. A departure of the present specification from earlier ones (other than a modified definition) is the inclusion of limits on optical rotation and nitrogen content. Their inclusion, and the numerical limits, are designed to ensure that as far as possible only gum from A. senegal or closely related species is able to satisfy the requirements (and that, for example, gum talha is excluded).

Although gum arabic intended for pharmaceutical use needs to be of high quality, the BP specification is not as demanding as the JECFA one. Neither optical rotation nor nitrogen content are specified.

Quality control measures in Sudan include a small laboratory at the cleaning and sorting warehouses in Port Sudan. Samples of gum are regularly checked and each export consignment receives a certificate giving analytical data such as moisture content, acid-insoluble matter and optical rotation.

Grades and prices

There are four main grades of Sudanese gum arabic (hashab), although two of these (HPS and Cleaned) are the main ones to enter international trade. The names of the four grades arise from the way in which the gum is cleaned and sorted. Small amounts of "Natural" gum (i.e., gum which has not been cleaned or sorted) used to be available but there is very little demand for this. In addition, since 1994, a processed grade (kibbled) has been available (see COLLECTION/PRIMARY PROCESSING). The grades and their export prices for 1994/95 (FOB Port Sudan) are as follows:
 
 
Kibbled  US$ 5 000/tonne 
HPS (Hand Picked Selected)  US$ 4 850/tonne 
Cleaned (or Clear Amber Sorts)  US$ 4 200/tonne 
Siftings  na 
Dust  US$ 2 760/tonne 

The prices are set by the organization which controls the whole system of gum arabic production in Sudan, the Gum Arabic Company. They are set just before the start of the tapping season (around September/October) and remain fixed for that year.

Gum talha from Sudan has traditionally only been sold as one grade but from 1995 it is being cleaned and graded to form three grades:
 
 
Super  US$ 950/tonne 
Standard Clean  US$ 850/tonne 
Siftings  US$ 400/tonne 

Nigerian gum arabic is sorted into three grades. The top grade (Grade 1) is gum produced from A. senegal, and although comparable to Sudanese Cleaned gum it is discounted in price by US$ 400?500/tonne. Grade 2 is gum produced from other species of Acacia (such as A. seyal and A. sieberana). Grade 3 gum is much darker and very mixed in quality; it may consist of gum from species other than Acacia (such as Combretum and Albizia). Prices in early 1994 (when Sudanese Cleaned gum was US$ 4 000/tonne) were:
 
 
Grade 1  US$ 3 500/tonne 
Grade 2  US$ 600-700/tonne 
Grade 3  na 

PLANT SOURCES

Botanical names

Family Leguminosae (Mimosoideae):

Acacia spp., especially:
A. senegal (L.) Willd.
A. seyal Del.

Numerous Acacia species yield gum, either by natural exudation or after tapping, but almost all gum arabic of commerce originates either from A. senegal or A. seyal. There is disagreement over some aspects of Acacia taxonomy but A. senegal is generally regarded as occurring as four varieties:

A. senegal (L.) Willd. var. senegal
(syn. A. verek Guill. & Perr.)
A. senegal (L.) Willd. var. kerensis Schweinf.
A. senegal (L.) Willd. var. rostrata Brenan
A. senegal (L.) Willd. var. leiorhachis Brenan
(syn. A. circummarginata Chiov.)

A. seyal occurs as two varieties:

A. seyal Del. var. seyal
A. seyal Del. var. fistula (Schweinf.) Oliv.

Other species of Acacia from which gum is, or has been, collected for local use or as minor components of poorer quality shipments for export include:

A. karroo Hayne
A. paoli Chiov.
A. polyacantha Willd.
A. sieberana DC.

Description and distribution

A. senegal var. senegal is the most widely distributed of the four varieties of A. senegal and the most important and best quality source of gum arabic. It is the only variety found in Sudan, where both natural stands and plantations are tapped. It is a small to medium sized thorny tree, with a stem which is irregular in form and often highly branched. In leaf, like many other Acacias, it has a dense, spreading crown. In common with other members of the A. senegal complex it has characteristic sets of prickles on the branches, usually in threes with the middle one hooked downward and the lateral ones curved upward. The bark is not papery or peeling. In Africa it occurs throughout the gum belt described earlier but is also found in the arid or semi?arid areas of Tanzania, Zambia, Zimbabwe and Mozambique. It has a limited occurrence in India and Pakistan.

The other varieties of A. senegal have a much more restricted distribution than var. senegal and provide only very tiny amounts of gum to the market. A. senegal var. kerensis has a slightly yellowish, sometimes peeling bark and smaller pods than var. senegal. It occurs in parts of Somalia, Uganda, Kenya and Tanzania. A. senegal var. leiorhachis is also found in parts of East Africa but it occurs also in Central and Southern Africa (Zambia, Zimbabwe, Botswana and South Africa). In Kenya it occurs in two growth forms: as a well-formed tree with spreading crown and as a "whippy" form in which three or four spindly branches extend upwards and away from the rest of the tree. A. senegal var. rostrata is also variable and occurs as a tree with flaking, papery bark or in a more shrubby form. It is mainly confined to parts of Central and Southern Africa.

A. seyal var. seyal is the source of gum talha and has a much more extended range than var. fistula. It has a single straight stem with a characteristic, pronounced colour, usually orange-red, to the powdery bark, and straight thorns rather than the curved prickles of A. senegal. It has a wide distribution in Africa and is found in most of the countries where A. senegal occurs; in Sudan it occurs in greater numbers than A. senegal. A. seyal var. fistula is distinguished from var. seyal by its creamy white bark and the presence of ant galls. It is limited to the eastern half of Africa and is not known to be used as a source of gum.

Gum from A. karroo is produced in Zimbabwe and South Africa, although the species has a much wider distribution. It occurs over a wide range of altitudes and in many different habitats. In Ghana, A. polyacantha and A. sieberana occur in the hotter, drier, northern parts of the country and are occasional sources of gum.

COLLECTION/PRIMARY PROCESSING

In Sudan and Nigeria, virtually all gum from A. senegal is obtained by tapping the trees; there is very little natural exudation. The reverse is true with A. seyal gum. In countries such as Kenya A. senegal does produce gum naturally and all of the gum which is collected comes from harvesting natural exudate.

The following account describes the collection, handling and primary processing (cleaning) of gum hashab - gum arabic from A. senegal - in Sudan. Tapping methods have been developed which do not damage the trees, and handling and cleaning practices have been optimized to produce a superior quality product.

Tapping begins when the trees are just starting to shed their leaves, usually about the end of October or beginning of November. After five weeks the first collections of gum are made, with further collections from the same trees at approximately 15-day intervals until the end of February, making five or six collections in total.

The older methods of making small incisions into the tree with an axe have largely been replaced by one which utilizes a specially designed tool, a "sunki". This has a metal head fixed to a long wooden handle. The pointed end of the head is pushed tangentially into the stem or branch so as to penetrate just below the bark, and then pulled up so as to strip a small length of bark longitudinally from the wood. Damage to the wood should be minimal. Several branches are treated in a similar manner at one tapping. In following years, other branches or the reverse side of the previously treated branch are tapped.

After this superficial injury, tears of gum form on the exposed surfaces and are left to dry and harden. As far as possible, the tears are picked by hand from the stems and branches where they have formed, and not by knocking to the ground where they can pick up dirt. They are placed in an open basket carried by the collector; the use of plastic sacks has been found to increase the risk of moisture retention and mould formation.

For trees which have been planted from seed, tapping starts at age 4-5 years; for those planted as seedlings, tapping can start in the third year.

In Sudan, the collector sells his gum at regular gum auctions, either to a trader who then sells it on to the Gum Arabic Company, or directly to the Company if they intervene because the price does not reach the guaranteed floor price. Any trader who buys gum then undertakes the process of cleaning and grading it. This is done by hand, usually by women, who sort it into piles of whole tears and smaller pieces, separating any dark gum and removing pieces of bark and other foreign matter.

The same principles of cleaning and sorting are followed in most other countries and the trader or trading organization then usually exports the graded gum. In Sudan, however, the cleaning process is repeated when the Gum Arabic Company receives consignments of gum from the regional centres at its export warehouses in Port Sudan. Since 1991 the cleaning operation has been mechanized using a system of conveyor belts and shaking and sieving machines. Final inspection of the cleaned gum and removal of any remaining foreign matter or dark coloured pieces is made manually as it moves on a belt to be bagged.

Yields

Yields of gum arabic from individual trees are very variable and little reliable data are available on which to base sound estimates of "average" yields. A figure of 250 g of gum per tree per season is often cited as an average yield. Yields of several kg or more have been reported from individual trees.

In Sudan, yields from cultivated A. senegal are said to increase up to the age of 15 years, when they level out and then begin to decline after 20 years. At this stage, if desired, trees can be coppiced and after a suitable period of time (and pruning) tapping can recommence on the new stems. In Mali, the best yields from A. senegal are said to be produced between ages seven and 15 years.

VALUE-ADDED PROCESSING

When imported into the consumer countries most gum arabic is further processed into kibbled and powdered forms. Kibbling entails passing whole or large lumps of gum through a hammer mill and then screening it to produce smaller granules of more uniform size. These pieces are more easily dissolved in water, and under more reproducible conditions, than the raw gum and so are preferred by the end-user.

As an extension to its mechanized cleaning process, Sudan recently installed machinery to produce kibbled gum arabic. In so doing, it became the first producer country to gain added value in this way. Production began during the 1993/94 season and approximately 2 500 tonnes of kibbled gum was produced.

Powdered gum may be produced from kibbled gum but it may also be produced by a process known as spray drying. This furnishes a high-quality, free-flowing powder with even better solubility characteristics than kibbled gum. The gum is dissolved in water, filtered and/or centrifuged to remove impurities and the solution, after pasteurization to remove microbial contamination, is sprayed into a stream of hot air to promote evaporation of the water. By altering atomizing conditions, powder can be produced with varying particle sizes and bulk densities, according to the end-user's requirements. Spray drying is an energy-intensive process and this, together with the requirements for large quantities of pure water, makes it something that most gum arabic producers could not consider. The difficulty of handling large volumes of aqueous solutions of gum in a producer country ? where ambient temperatures are high ? without suffering unacceptable increases in the microbiological load adds further to the problem.

PRODUCTS OTHER THAN GUM

No other items of trade are produced from the gum-yielding Acacias, although they are used locally as sources of fuelwood. Many species of Acacia are important sources of browse for livestock.

DEVELOPMENTAL POTENTIAL

A. senegal has been widely planted in Sudan and some other countries as a means of combating the process of desertification; it has also been used more generally for afforestation of arid tracts and soil reclamation. As well as environmental benefits, A. senegal provides socio-economic benefits to many thousands of communities in the "gum belt" through the production of gum arabic. In Sudan, especially, tending the "gum gardens" remains an integral way of life for many people and a valuable source of cash income.

However, demand for gum arabic is such that importers in end-user countries are always keen to encourage new sources of supply to supplement traditional sources. Thus, in recent years, Kenya has emerged as a new supplier of gum arabic to the world market, albeit a tiny one in comparison to most of the established African producers. However, the Kenyan experience is one which could be followed in some other African countries. In the semi-arid areas where A. senegal is found, the local people are often pastoralists involved in herding activities. Climatic and ecological conditions are not favourable to agriculture and there are few opportunities for growing cash crops. In these circumstances production of gum arabic ? either from an existing, wild resource of a suitable Acacia species or from A. senegal planted as part of an agroforestry system ? can generate much-needed cash.

A further attraction of promoting gum arabic collection under the conditions described above is that the realization by the local people that an economic value can be placed on the trees is likely to encourage them to preserve the trees and not to cut them down so readily for use as fuelwood as happens at present.

There are therefore numerous benefits to be gained from the production of gum arabic, either through the utilization of natural stands of Acacia or from planted sources, providing it is carried out in a sustainable manner. If due attention is given to the production of high quality gum (in particular, that gum from different Acacia species is not mixed) then not only can a new producing country aim to meet domestic needs, but it should also be capable of entering the export market.

Research needs

Of the gum-yielding Acacias, most research on agronomic aspects has concentrated (justifiably) on A. senegal, although further work remains to be done. Chemical analysis and quality assessment has been carried out on gum exudates from a large number of Acacia species (as well as gum arabic-like exudates from other genera), but relatively little detailed information is available on the intra-specific variation of A. senegal gum. Some areas requiring further research are therefore:

SELECTED BIBLIOGRAPHY

ANDERSON, D.M.W. (1993) Some factors influencing the demand for gum arabic (Acacia senegal (L.) Willd.) and other water-soluble tree exudates. Forest Ecology and Management, 58, 1-18.

ANDERSON, D.M.W., BRIDGEMAN, M.M.E., FARQUHAR, J.G.K. and McNAB, C.G.A. (1983) The chemical characterization of the test article used in toxicological studies of gum arabic (Acacia senegal (L.) Willd.). The International Tree Crops Journal, 2, 245-254.

ANDERSON, D.M.W., BROWN DOUGLAS, D.M., MORRISON, N.A. and WEIPING, 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. and WEIPING, W. (1991) Gum arabic (Acacia senegal) from Niger - comparison with other sources and potential agroforestry development. Biochemical Systematics and Ecology, 19(6), 447-452.

ANDERSON, D.M.W. and PINTO, G. (1980) Variations in the composition and properties of the gum exuded by Acacia karroo Hayne in different African locations. Botanical Journal of the Linnean Society, 80(1), 85-89.

ANDERSON, D.M.W. and WEIPING, W. (1991) Acacia seyal and Acacia sieberana sources of commercial gum talha in Niger and Uganda. The International Tree Crops Journal, 7(1/2), 29-40.

AWOUDA, El?H.M. (1988) Outlook for gum arabic production and supply. pp 425-434. In Gums and Stabilisers for the Food Industry, Vol. 4. Proceedings of 4th International Conference, Wrexham, July, 1987. Oxford: IRL Press.

AWOUDA, El?H.M. (1990) Indicators for present and future supply of gum arabic. pp 45-54. In Gums and Stabilisers for the Food Industry, Vol. 5. Proceedings of 5th International Conference, Wrexham, July, 1989. Oxford: IRL Press.

BADI, K.H., AHMED, A.E.H. and BAYOUMI, A.A.M.S. (1989) The Forests of Sudan. 184 pp. Khartoum: Ministry of Agriculture, Department of Forestry.

BARBIER, E.B. (1992) Rehabilitating gum arabic systems in Sudan: economic and environmental implications. Environmental and Resource Economics, 2(4), 341-358.

BESHAI A.A. (1984) The economics of a primary commodity: gum arabic. Oxford Bulletin of Economics and Statistics, 46(4), 371-381.

BHATT, J.R. and RAM, H.Y.M. (1990) Ethephon-induced gum production in Acacia senegal and its potential value in the semi-arid regions of India. Current Science, 59(23), 1247-1250.

BOOTH, F.E.M. and WICKENS, G.E. (1988) Acacia senegal. pp 1?7; Acacia seyal. pp 8?12. In Non-Timber Uses of Selected Arid Zone Trees and Shrubs in Africa. 176 pp. FAO Conservation Guide 19. Rome: Food and Agriculture Organization.

BP (1993) Acacia. pp 19?20. In British Pharmacopoeia, Vol. 1. London: Her Majesty's Stationery Office.

DIONE, M. and VASSAL, J. (1993) [Experimental study on the means of production of gum trees of Acacia senegal: looking back on the gum tree development programmes in the Senegalese Sahel] (in French). pp 22-41. In Proceedings of 5th Sahel Workshop: Natural Resources and Social Conflicts in the Sahel, 4?6 January, 1993. Aarhus, Denmark: Aarhus University Press.

DSS (1993) Gum Arabic. A Potential Source of Income for the Mukogodo Community- [in Kenya]. Report by Department of Social Services. 14 pp. Nairobi: Ministry of Culture and Social Services.

FAGG, C.W. and STEWART, J.L. (1994) The value of Acacia and Prosopis in arid and semi-arid environments. Journal of Arid Environments, 27(1), 3-25.

FAO (1992) Gum arabic [published in FAO Food and Nutrition Paper 49, 1990]. pp 735?737. In Compendium of Food Additive Specifications. FAO Food and Nutrition Paper 52 (Joint FAO/WHO Expert Committee on Food Additives. Combined Specifications from 1st through the 37th Meetings, 1956-1990). Rome: Food and Agriculture Organization.

GIFFARD, P.L. (1975) [Gum trees for the reafforestation of Sahelian regions] (in French). Bois et Forêts des Tropiques, (161), 3?21.

GLICKSMAN, M. and SAND, R.E. (1973) Gum arabic. pp 197-263. In Industrial Gums. Whistler, R.L. (ed.). 810 pp. New York: Academic Press.

GUINKO, S. (1991) [Study of the role of the Acacias in rural development in Burkina Faso and Niger] (in French). Ouagadougou, Aug., 77 pp.

HALL, J.B. and McALLAN, A. (1993) Acacia Seyal: A Monograph. 88 pp. Bangor, UK: School of Agricultural and Forest Sciences, University of Wales.

HANSON, J.H. (1992) Extractive economies in a historical perspective: gum arabic in West Africa. Advances in Economic Botany, 9, 107-114.

JAMAL, A. (1994) Major insect pests of gum arabic trees Acacia senegal Willd. and Acacia seyal L. in Western Sudan. Journal of Applied Entomology, 117(1) 10?20.

JAMAL, A. AND HUNTSINGER, L. (1993) Deterioration of a sustainable agro-silvo-pastoral system in the Sudan: the gum gardens of Kordofan. Agroforestry Systems, 23(1), 23-38.

JAYASINGHE, S. (1981) Plant gum exudates - an unexploited forest resource of Sri Lanka [includes Acacia and Sterculia spp.]. The Sri Lankan Forester, 15(1-2), 54-60.

JURASEK, P., KOSIK, M. and PHILLIPS, G.O. (1993) A chemometric study of the Acacia (gum arabic) and related natural gums. Food hydrocolloids, 7(1), 73-85.

JURASEK, P., KOSIK, M. and PHILLIPS, G.O. (1993) The classification of natural gums. III. Acacia senegal and related species (gum arabic). Food hydrocolloids, 7(3), 255-280.

LARSON, B.A. and BROMLEY, D.W.(1991) Natural resource prices, export policies and deforestation: the case of Sudan. World Development, 19(10), 1289?1297.

MISRA, C.M. and SINGH, S.L. (1985) Suitable tapping technique of gum from Acacia nilotica (Babool). Van Vigyan, 23(1/2), 10-12.

NAS (1981) Acacia. Gum arabic. p 7. In Food Chemicals Codex. Third edition, 735 pp. Washington, DC: National Academy Press.

OSMAN, M.E., MENZIES, A.R., WILLIAMS, P.A. and PHILLIPS, G.O. (1994) Fractionation and characterization of gum arabic samples from various African countries. Food Hydrocolloids, 8(3/4), 233-242.

OSMAN, M.E., WILLIAMS, P.A., MENZIES, A.R. and PHILLIPS, G.O. (1993) Characterization of commercial samples of gum arabic. Journal of Agricultural and Food Chemistry, 41(1), 71?77.

PEARCE, D.W., BARBIER, E.B. and MARKANDYA, A. (1990) Natural resources in the economy of the Sudan. pp 117-149. In Sustainable Development: Economics and Environment in the Third World. Aldershot, UK: Edward Elgar Publishing.

PHILIP, M.S. (1975) Gum Arabic and Acacia Senegal. Nigerian Forestry Information Bulletin No. 29. 12 pp.

ROBBINS, S.R.J. (1988) Gum arabic. pp 18-33. In A Review of Recent Trends in Selected Markets for Water-Soluble Gums. ODNRI Bulletin No. 2. 108 pp. London: Overseas Development Natural Resources Institute [now Natural Resources Institute, Chatham].

VAN DEN BERGH, J. (1986) [The Acacia gum tree, tree resource of the Sahel] (in French). Afrique Agriculture, (132), 10-17.

VASSAL, J. and MOURET, M. (1989) [Preliminary results of trials of some Australian Acacia species in southern Corsica [for gum production]] (in French). Forêt Méditerranéenne, 11(2), 113-120.

__________________________________

3/ These specifications are currently (mid-1995) under review by JECFA and it is planned to publish revised ones in 1996
 
 

Table 6. Gum arabic: imports into the European Community, and sources, 1988?93
(tonnes)
  1988  1989  1990  1991  1992  1993 
Total  23797  26151  27630  32102  29963  26500 
Of which from :
Sudan  9963  12463  14400  17098  10215  9304
Nigeria  3471  3538  4385  3568  7243  4759 
France  1876  2365  1993  2104  3003  2624 
UK  2293  1373  1698  1855  2512  1746 
Chad  1443  1469  1059  2153  2422  3527 
Germany  726  838  670  997  1353  1177 
Senegal  716  301  276  273  245  449 
Cameroon  344  345  302  75  573  841 
India  121  452  587  435  469  369 
USA  439  355  432  978  316  163
Netherlands  75  138  1043  1296  184  87 
Mauritania  200  595  32  48  55 
Mali  187  391  69  75  32  77 
Tanzania  88  31  27  118  160  176 
Ethiopia  74  256  68  20  43  27 
Somalia  24  21  82  38  49 
Niger  41  60  20  155  169 
Central African Republic  74  72  74  79  33 
Ghana  93  212  -
Kenya  18  121  102 
Soviet Union, former  1077  20 

Source: Eurostat
 
 

Table 7. Gum arabic: imports into the European Community from Sudan, and destinations, 1988-93
(tonnes)
  1988  1989  1990  1991  1992  1993 
Total  9963  12463  14400  17098  10215  9304 
Of which to :
France  3016  3815  5023  7074  5219  5118 
UK  2580  3176  3053  2521  2118  1168 
Italy  2205  2645  2675  3431  1007  1935 
Germany  1265  1659  1388  1804  1027  478 
Denmark  441  716  755  727  608  440 
Belgium/Luxembourg  261  200  360  280  80  120 
Spain  129  159  96  90  56  45 
Greece  65  90  50  31 
Netherlands  1000  1140  100 
Portugal 
Ireland 

Source: Eurostat
 
 
 

Table 8. Gum arabic: imports into the European Community from Nigeria,
and destinations, 1988-93
(tonnes)
  1988  1989  1990  1991  1992  1993
Total  3471  3538  4385  3568  7243  4759 
Of which to :
France  437  437  403  167  1256  1152 
UK  1982  2204  2862  2411  3244  2315 
Italy  38 
Germany  974  873  1119  990  2734  1237 
Denmark  54 
Belgium/Luxembourg  12 
Spain  12  14 
Greece  10 
Netherlands  10 
Portugal  -
Ireland 

Source: Eurostat
 
 

Table 9. Gum arabic: imports into the United States, and sources, 1991-94
(tonnes)
  1991  1992  1993  1994 
Total  8313  5802  5508  10434 
Of which to :
Sudan  5480  2471  1800  167 
France  2511  2430  2699  5367 
UK  278  678  740  2951 
Nigeria  143  81  524 
Chad  18  60  1061 
India  18  102 
Germany  12  22 
Egypt  35  10 
Kenya  80  34 
Western Sahara  20 
Somalia 
Djibouti 

Source: National statistics
Table 10. Gum arabic: imports into Japan, and sources, 1988-94
(tonnes)
  1988  1989  1990  1991  1992  1993  1994 
Total  1656  1821  2735  2022  2019  1219  1804 
Of which from :
Sudan  1606  1791  2702  1983  1644  741  1447 
France  16  10  20  12  60  145  200 
UK  20  176  245  110 
USA  28  12  62  43  38 
Nigeria  20 
Guinea Bissau  20 
Kenya  12 
India  20  -

Source: National statistics
 
 
 

Table 11a. Gum arabic: production in Sudan (5-year annual averages), 1960-94
(tonnes)
 
  1960-64  65-69  70-74  75-79  80-84  85-89  90-94 
Annual average  46550  50576  35073  37408  31079  23721  18358 
Of which :
Gum hashab  44299  47434  30910  36026  26721  19777  15038 
Gum talha  2251  3142  4163  1382  4358  3944  3320 

Source: Gum Arabic Company, Sudan
 
 

Table 11b. Gum arabic: production in Sudan, 1988-94
(tonnes)
  1988  1989  1990  1991  1992  1993  1994 
Total  26000  28948  25733  12351  7616  12865  33227 
Of which :
Gum hashab  20000  24256  22408  11756  7439  11410  22178 
Gum talha  6000  4692  3325  595  177  1455  11049 

Source: Gum Arabic Company, Sudan
 
 
 

Table 12. Gum arabic: exports from Sudan, 1988-94
(tonnes)
  1988  1989  1990  1991  1992  1993  1994 
Total  18603  19352  26912  24978  14068  15730  22735 
Of which :
Gum hashab  16672  17385  22960  21543  8198  9925  18339 
Gum talha  1931  1967  3952  3435  5870  5805  4396 

Source: Gum Arabic Company, Sudan
 
 
 


KARAYA

DESCRIPTION AND USES

Karaya gum is the dried exudate obtained from trees of Sterculia species. Most gum is of Indian origin, although increasing amounts come from Africa. The gum enters trade as irregular-shaped or broken tears, with colour ranging from whitish or tan in the better grades to dark brown in the lower grades. In the early years of large-scale, commercial use it was sometimes used as an inferior substitute for tragacanth, and this led to its alternative name of Indian Tragacanth.

Karaya is an acidic, partially acetylated polysaccharide. It absorbs water very rapidly to form viscous mucilages at low concentrations, although it is one of the least soluble of the gum exudates. Although it does have food use ? in Europe it has been assigned the food additive number E416 ? its usage is overwhelmingly in pharmaceutical, dental or other medical applications, particularly those which make use of karaya's strong adhesive properties. A very minor amount is used in miscellaneous industrial applications such as papermaking and textiles.

Pharmaceutical and related use

The three most important uses of karaya are as a dental adhesive for false teeth, in the manufacture of colostomy bag fixings, and as a bulk laxative. In the first two applications there has been some substitution of karaya by cheaper carboxymethylcellulose derivatives, although recent American trade reports have suggested that some of these substitutes are not as effective as karaya. An Indian market study (ANON., 1987) reported that in France and the United Kingdom, 95% of imported karaya is used in pharmaceutical products; in the United States and Japan, the proportion was about 85%.

Food use

In foods, karaya is used in small amounts as a texturizer and stabilizer in ice creams, and in ice sherbets to prevent the formation of ice crystals. Its stability in acid media makes it suitable for addition to salad dressings, sauces, cheese spreads and some other products.
 

WORLD SUPPLY AND DEMAND TRENDS

Markets

Throughout the late 1960s to mid-1980s, Indian exports of karaya were in the range 4 000-6 000 tonnes/year - more than that of all other Indian gums and resins combined ? and the United States, France and the United Kingdom (in that order) were the biggest importers. Average exports for the period 1977/78-1982/83 were approximately 5 700 tonnes/year (ROBBINS, 1988).

More recent data, for the years 1987/88-1993/94, are given in Table 13. The six-year annual average for 1987/88-1992/93 is less than 1 300 tonnes, a sharp decline on the same period a decade earlier. The United States, France and the United Kingdom remain the biggest markets for karaya, although demand in the United States has fallen to such a degree that France is now the main importing country. Approximate annual averages over the whole of the recent period are: France 400 tonnes, United States 360 tonnes and the United Kingdom 210 tonnes; Japan is the next biggest single market (110 tonnes). Germany, Italy, Belgium and the Netherlands have also imported directly from India in most years (averaging 130 tonnes/year between them) so Europe as a whole is about twice the size of the American market.

Indian government controls over pricing and exports of karaya in the late 1980s, which some trade sources feel contributed to the poor supply situation caused by restrictions on tapping and low productivity, have now been relaxed, although there are mixed views in the trade as to whether karaya can regain its former position in the international market.

India is traditionally the biggest producer and exporter of karaya but increasing amounts of gum enter international trade from Africa. The quantities involved are very uncertain but if the data for Senegal in Table 2 (imports into the EC of gums and resins excluding gum arabic) refer mainly to karaya, then they could amount to around 1 000 tonnes or more annually.

Domestic consumption of karaya in India was (and still is) considerable. No recent data are available but in 1972, for example, it was about twice the volume of exports.

Supply sources

India remains the biggest producer of karaya and, apart from lac, karaya is still India's most important export item in the gums and resins category. However, the data in Table 13 indicate a sharp fall in exports in 1990/91 from the previous year, with an all-time low of 570 tonnes in 1991/92. It is not known to what extent supplies from Africa made up for the drop in Indian exports. Since then, Indian exports have recovered somewhat, although they are still below the level at the beginning of the period shown in Table 13, and considerably below the levels a decade earlier.

In Africa, Senegal is the biggest producer of karaya and significant quantities are exported to France and the United Kingdom. Sudan also exports small amounts although it has the potential to produce and export much more.

Quality and prices

There are at least five Indian grades of karaya: HPS (Hand Picked Selected), Superior No.1 and No. 2, FAQ (Fair Average Quality) and Siftings. The first four grades are the main export grades. The main quality criteria at the sorting stage are colour and foreign matter, although even after grading the quality of consignments is often variable. The higher grades should be cleaner and paler than the lower ones, which may be dark brown in colour and have bits of bark present.

A BP specification exists for pharmaceutical grade karaya, and FAO and Indian specifications have been published for karaya intended for food use.

Indicative FOB prices quoted by importers in London for Indian karaya (mid-1995) are in the range US$ 2 250-6 000/tonne according to grade. FAQ gum is about US$ 3 000/tonne. Senegalese gum has two grades, hand-picked and standard, which are generally inferior to the Indian export grades, and this is reflected in lower prices.

PLANT SOURCES

Botanical/common names

Family Sterculiaceae:

Sterculia urens Roxb.
S. villosa Roxb.
S. setigera Del.

Description and distribution

S. urens is a deciduous tree, up to 15 m high. It has a smooth, greyish white or reddish bark, which peels off in papery flakes. In India it occurs wild in many places on the dry, rocky hills and plateaus of central and northern regions, but it is also grown in plantations as a timber crop. The greater proportion of recent production has come from Andhra Pradesh state.

S. villosa is a small to moderate sized, spreading tree, distributed in the sub-Himalayan tract of India from the Indus eastwards, as well as more southern regions.

Several species of Sterculia occur in Africa but S. setigera is the only species known to be exploited commercially for gum. It grows up to 15 m tall and has papery, peeling bark.

COLLECTION/PRIMARY PROCESSING

There is some natural exudation of karaya but most gum is collected by tapping. Descriptions of the tapping vary somewhat according to the source of the information, but all entail removal of sections of bark from the trunk of the tree. Guidance rules have been laid down by the Forest Research Institute, Dehra Dun, in India, but in practice the rules are not adhered to and the dimensions of the "blaze" are often exceeded. Tapping which involves deep and wide wounds to the tree to maximize gum yields is damaging to the tree, and this led to a ban on tapping by one Indian Forestry Department in the 1980s.

In India, tapping should be confined to trees with a minimum girth of 90 cm and the initial size of the blaze should be limited to 15 cm tall, 10 cm wide and 0.5 cm deep. Sixteen successive visits should be made to the tree at two-week intervals, removing a further 2?cm high section of bark above the previous one at each visit, and leading to a maximum depth of the blaze of 2.5?3.0 cm. An additional blaze can be worked for every 50 cm girth increment above 90 cm, providing sufficient space is left between adjacent blazes. By staggering the position of each new season's blazes it is possible to leave a rest period of six years before returning to a previous one, by which time the scar should have healed. Tapping is best done during the hot season to maximize yields.

In India, the collected gum is usually sold by auction to government agencies in each of the producing states, who then undertake final cleaning, drying and grading of the gum.

Yields

No reliable data are available but the yield of gum from mature trees has been variously estimated at 1-5 kg/tree during a season.

VALUE-ADDED PROCESSING

Imported gum is purified by size reduction and removal of pieces of bark by air flotation methods. Other mechanical methods are used to remove sand, dirt and other types of foreign matter.

PRODUCTS OTHER THAN GUM

The wood finds some use although it is not a high class timber. It has been employed for making packing cases, match splints, pencils, picture frames and other miscellaneous items.

DEVELOPMENTAL POTENTIAL

The market appears willing to take good quality gum if it is available, as evidenced by the recent upturn in Indian exports, and pharmaceutical usage of karaya seems to be firm. However, opportunities for exploiting market demand are likely to rest more with existing producers, especially those in Africa with underexploited stands of Sterculia, than with new ones. Sudan has very large areas of Sterculia and if attention is paid to harvesting and cleaning the gum to produce material of high quality - as it is for gum arabic - then it certainly has the potential to supply much larger quantities of gum than it does at present.

Research needs

Improvement of harvesting, cleaning and handling practices, coupled with market studies, is required more than basic research. Trade evaluation should be undertaken of large, representative collections of gum, by those countries having the raw material resource, in order to ascertain the scope for increased production and to gain the confidence of end-users that they would be a reliable, consistent supplier of gum.

SELECTED BIBLIOGRAPHY

ANON. (1973) Karaya Gum from Sterculia Urens Roxb. Industrial Series No. 7. Dehra Dun, India: Forest Research Institute and Colleges.

ANON. (1976) Sterculia. pp 43?49. In The Wealth of India. Raw Materials, Vol. 10. New Delhi: Council for Scientific and Industrial Research.

ANON. (1987) Market Survey for Select Minor Forest Products in France, UK, USA and Japan. 157 pp. New Delhi: Indian Institute of Foreign Trade.

BABU, A.M. and MENON, A.R.S. (1989) Ethephon-induced gummosis in Bombax ceiba L. and Sterculia urens Roxb. Indian Forester, 115(1), 44?47.

BP (1993) Sterculia. p 631. In British Pharmacopoeia, Vol. 1. London: Her Majesty's Stationery Office.

BIS (1985, reaffirmed 1990) Specification for gum karaya. Indian Standard IS: 5025?1985. 6 pp. New Delhi: Bureau of Indian Standards.

BIS (1988) Specification for gum karaya, food grade. Indian Standard IS: 12408?1988. 6 pp. New Delhi: Bureau of Indian Standards.

FAO (1992) Karaya gum [published in FAO Food and Nutrition Paper 38, 1988]. pp 821?823. In Compendium of Food Additive Specifications. FAO Food and Nutrition Paper 52 (Joint FAO/WHO Expert Committee on Food Additives. Combined Specifications from 1st through the 37th Meetings, 1956?1990). Rome: Food and Agriculture Organization.

GAUTAMI, S. and BHAT, R.V. (1992) A Monograph on Gum Karaya. Hyderabad, India: National Institute of Nutrition, Indian Council of Medical Research.

GOLDSTEIN, A.M. and ALTER, E.N. (1973) Gum karaya. pp 273?287. In Industrial Gums. Whistler, R.L. (ed.). 810 pp. New York: Academic Press.

GUPTA, T. and GULERIA, A. (1982) Gums and resins. pp 73?84. In Non-Wood Forest Products in India: Economic Potentials. 147 pp. New Delhi: Oxford & IBH.

JAYASINGHE, S. (1981) Plant gum exudates ? an unexploited forest resource of Sri Lanka [includes Acacia and Sterculia spp.]. The Sri Lankan Forester, 15(1?2), 54?60.

ROBBINS, S.R.J. (1988) Gum karaya. pp 61?66. In A Review of Recent Trends in Selected Markets for Water-Soluble Gums. ODNRI Bulletin No. 2. 108 pp. London: Overseas Development Natural Resources Institute [now Natural Resources Institute, Chatham].

SHAH, J.J. (1983) Gum, resin and gum-resin secretion in plants. Acta Botanica Indica, 11(2), 91?96.

SHIVA, M.P., SINGH, N.P. and THAKUR, F.R. (1994) New designed improved gum tapping tools. MFP News (Centre of Minor Forest Products, Dehra Dun, India), 4(1), 8?11.

SINGH, M. (1981) Potentialities for gum collection in Maharashtra and Gujurat. Khadi Gramodyog, 27(5), 288?290.

VERMA, V.P.S. and KHARAKWAL, G.N. (1977) Experimental tapping of Sterculia villosa Roxb. for gum karaya. Indian Forester, 103(4), 269?272.
 
 

Table 13. Karaya: exports from India, and destinations, 1987/88-1993/94a
(tonnes)
  87/88  88/89  89/90  90/91  91/92  92/93  93/94 
Total  2001  1831  1628  599  574  843  1443 
Of which to :
USA  708  604  467  215  105  178  287 
France  543  466  496  124  112  373  729 
UK  485  346  305  17  52  118  181 
Japan  123  113  138  78  132  78  133 
Germany  58  167  122  50  61  44  35 
Italy  48  59  30  50  30  23  16 
Belgium  14  26  10  34 
Netherlands  10  15  15 
Thailand  23 
Malaysia 
Singapore 
Norway  21  25 
Czechoslovakia,former  22 
Oman  13 
Bermuda  13 
Hong Kong 
United Arab Emirates  19  19 

Source: National statistics

Note: a Year runs April-March

 


 

TRAGACANTH

DESCRIPTION AND USES

Tragacanth gum is the dried exudate produced by tapping the tap root and branches of certain shrubby species of Astragalus, particularly those which occur wild in Iran and Turkey. The gum is exported from the country of origin in ribbon or flake form, and has a rather horny texture. Chemically, it is a complex mixture of acidic polysaccharides, mostly present as calcium, magnesium and potassium salts.

Tragacanth swells rapidly in water to form highly viscous colloidal sols or semi-gels, which act as protective colloids and stabilizing agents. The high viscosity of tragacanth solutions results from the molecular characteristics of the gum, and these depend on the grade and physical form of the gum, and the manner in which it is taken up in water. For example, the same concentration of solution prepared from whole gum is more viscous than one prepared from powdered gum. Unlike many other gums, solutions of tragacanth have a very long shelf life without loss of viscosity.

The most important applications of tragacanth are now in foods and pharmaceuticals. Its use for other, industrial purposes has declined over the years as cheaper alternatives to tragacanth have been developed.

Food use

In Europe, tragacanth has the food additive number E413. Its use in foods is not nearly so extensive now as it was some years ago, when it was widely used in salad dressings and sauces, savoury spreads, milk shakes, ice creams, and confectionery and bakery products. It functions as a thickener, stabilizer or emulsifier, but for many of these applications its advantage over other gums is its stability under acid conditions. Despite this, however, its high price has meant that for some of these end uses it has now been replaced by guar or xanthan gums.

Pharmaceutical use

Tragacanth has long been an important gum for pharmaceutical use: as a binder, suspender or emulsifier in tablets, ointments, lubricating jellies and oral suspensions, and particularly in dermatological creams and lotions. It is also used in toothpastes, hair lotions and other personal care products.

WORLD SUPPLY AND DEMAND TRENDS

Markets

In the 1950s, Iranian exports of tragacanth exceeded 4 000 tonnes/year (90% of it in flake form, the rest in ribbon); the United States and the United Kingdom were the major importers. Political upheavals and military conflict in the late 1970s and 1980s led to shortages of gum from Iran and a sharp increase in prices. Severe competition from other, cheaper gums, particularly xanthan gum, has resulted in a greatly diminished market for tragacanth.

ROBBINS (1988) estimated the world market for tragacanth to be no more than 500 tonnes/year; almost half of this was estimated to be consumed in Western Europe. Severe problems are encountered in estimating consumption of tragacanth: firstly, export data from the major producers (Iran and Turkey) are not easily accessed and, secondly, tragacanth is not listed separately in the trade statistics of many importing countries.

Japan does treat tragacanth separately, however, and Japanese imports during the period 1988-94 are shown in Table 14; they averaged just under 30 tonnes/year. This is not much different to the situation in the early 1980s, although in 1979 imports into Japan were over 100 tonnes.

In the United States, a 1987 trade embargo which prohibits the import of most goods from Iran has influenced direct imports of tragacanth, although the United States still imports the gum from European dealers.

In the absence of any reliable data, and in the light of news items in the trade literature which continue to speak of shrinking usage, it is estimated that world demand for tragacanth is probably in the region of 300 tonnes/year.

Supply sources

Iran and Turkey have been the only significant producers of tragacanth for some years, with Iran being the principal source. They are both listed as sources in Japanese import statistics (Table 14); tragacanth from the other countries represents re-exports (the only Indian shipment may be karaya, sometimes known as Indian tragacanth).

Trade sources in London report that production in Turkey has now virtually ceased, due to the poor financial returns to the collectors.

Quality and prices

Tragacanth is bought from origin as ribbons or flakes; loss of viscosity of gum which has been powdered and stored for long periods means that powdered tragacanth is always produced in the importing country. Iranian tragacanth, which is generally regarded as superior to Turkish, is sold in about 12 different grades: five ribbon (Ribbon no. 1, Ribbon no. 2, etc.) and the remainder flake.

Ribbon no. 1 is the top grade, being the palest and cleanest. Ribbon grades are usually used for pharmaceutical purposes; flake is used for food applications. The lower flake grades are appreciably darker and contain some foreign matter. When powdered for the end-user, tragacanth is sold and specified by viscosity.

An FAO specification exists for food grade tragacanth and includes limits on arsenic, lead and heavy metals, as well as some other parameters. Tragacanth is also specified in many pharmacopoeias for pharmaceutical use, including the British Pharmacopoeia.

Trade sources in London quote current (mid-1995) prices at around US$ 22/kg FOB for the top grade (Ribbon no. 1), US$ 16/kg for Ribbon no. 4 and falling to US$ 3-4/kg for the lowest grades. These prices are higher than they were a year earlier although, historically, tragacanth has always been one of the most highly priced gums, and has been considerably higher in some previous years. In the mid-1980s it fetched around US$ 20-70/kg, depending on grade.

PLANT SOURCES


Botanical names

Family Leguminosae (Papilionoideae): Astragalus spp.

Astragalus is a very large genus and includes many Asian species. A. gummifer Labill. is usually cited as the source of tragacanth but there is surprisingly little evidence to support this, and it is likely that other species which occur in the gum producing areas contribute to the total amount which enters world trade; whether to a greater or lesser degree then A. gummifer is not known. These other species include A. adscendens Boiss., A. echidnaeformis Sirjaev, A. gossypinus Fisch., A. kurdicus Boiss. and A. microcephalus Willd. Numerous other Astragalus species occur in the region.

Description and distribution

The better gum-yielding species are small, low, bushy perennials, frequently with a cushion-like form. However, they have relatively large tap roots and it is these which are the primary source of the gum. A. gummifer is a low shrub, up to 1 m tall, and is thorny and branching. A. microcephalus, which produces a high quality gum, is a low, spreading bush, 8-12 cm tall.

The Asiatic species of Astragalus, which are the sources of commercial gum, are native to countries of Asia Minor: Iran, Turkey, Iraq, Syria, Lebanon, Afghanistan and parts of Russia. They are usually found in the drier mountainous regions, although they require some water.

COLLECTION/PRIMARY PROCESSING

The most striking feature of the gum-producing Astragalus is a central gum cylinder in the tap root, which is contained by the woody cylinder and may be as much as half the total diameter of the root. The gum is contained in the cylinder at high pressure and, when cut, exudes rapidly and hardens into the characteristic ribbons of tragacanth.

Some gum is collected from spontaneous exudation but most is obtained by tapping. The process of tapping entails clearing away the earth surrounding the tap root and making one or two cuts into the upper part of the root. The cuts are usually made longitudinally or cross-angled to the root, 2-5 cm long. Sometimes the branches are also cut but this usually yields an inferior gum. After a period of time which varies according to local custom or circumstances, but may be a few days or a week or more, the tapper returns to the plants he has cut to collect the gum. Further collections may be made thereafter but the quality of the gum soon deteriorates to a point when it is not worth while to continue. Flakes of gum, rather than ribbons, are usually produced later in the season.

Tapping is carried out in the dry summer months and continues until the autumn rains. The collector sells the gum to the local merchant who then sells it on to the main trader. He, in turn, takes it to the main sorting and grading centre where it is graded and packaged for export.

Yields

GENTRY (1957) lists a number of factors which influence gum yields. Some species are intrinsically better yielders than others. Older plants, and those with a large gum cylinder in the root, produce greater quantities of gum, and good spring rains prior to tapping also favour gum production. Unlike exudate gums obtained from the trunks of trees, where warm sunlight shining on the tree increases gum flow, most exudation of tragacanth occurs at night, under conditions which minimise drying out of the gum and maintain the outward flow under high osmotic pressure.

Based on experimental fieldwork, Gentry estimated the average yield of gum from A. microcephalus at 15 g per 100-day tapping season.

VALUE-ADDED PROCESSING

As has been noted earlier, further processing such as grinding the gum to a powder is only done in the importing country, usually immediately before onward shipment to an end-user, so as to minimize loss of viscosity. Careful grinding, classifying according to particle size and, if necessary, blending, is essential to produce tragacanth gum of the prescribed viscosity.

PRODUCTS OTHER THAN GUM

No other products of economic value are obtained from the bushes.

DEVELOPMENTAL POTENTIAL

The decline in consumption of tragacanth gum is largely due to the high price brought about by the shortage of supply. If it were available in greater quantities, and at a lower price, it would be the gum of choice in most of its traditional applications. On the other hand, once end-users have switched to cheaper alternatives it is expensive for them to return to previous formulations. Much depends on the end-user. If Astragalus could be cultivated and gum produced at a cost which would make it significantly cheaper to the end-user than at present, then it may be possible to regain some markets. In these circumstances, Astragalus would be a crop worth developing in those countries with the appropriate ecological conditions for it to grow well.

Research needs

It is odd that so little research appears to have been carried out on the cultivation of Astragalus, given the high value of the product obtained from it. Gentry made some theoretical estimates of gum yield from cultivated plots based on 25 000 plants/ha and 15 g/plant (= 375 kg/ha). The following aspects need to be researched:

SELECTED BIBLIOGRAPHY

BP (1993) Tragacanth. pp 679-681. In British Pharmacopoeia, Vol. 1. London: Her Majesty's Stationery Office.

DUKE, J.A. (1981) Astragalus gummifer. pp 24-26. In Handbook of Legumes of World Economic Importance. 345 pp. New York: Plenum Press.

FAO (1992) Tragacanth gum [published in FAO Food and Nutrition Paper 34, 1986]. pp 225-227. In Compendium of Food Additive Specifications. FAO Food and Nutrition Paper 52 (Joint FAO/WHO Expert Committee on Food Additives. Combined Specifications from 1st through the 37th Meetings, 1956-1990). Rome: Food and Agriculture Organization.

GECGIL, A.S., YALABIK, H.S. and GROVES, M.J. (1975) A note on tragacanth of Turkish origin. Planta Medica, 27, 284-286.

GENTRY, H.S. (1957) Gum tragacanth in Iran. Economic Botany, 11(1), 40-63.

GENTRY, H., MITTLEMAN, M. and McCROHAN, P. (1992) Introduction of chia and gum tragacanth, new crops for the United States. Diversity, 8(1), 28-29.

MEER, G., MEER, W.A. and GERARD, T. (1973) Gum tragacanth. pp 289-299. In Industrial Gums. Whistler, R.L. (ed.). 810 pp. New York: Academic Press.

ROBBINS, S.R.J. (1988) Gum tragacanth. pp 52-60. In A Review of Recent Trends in Selected Markets for Water-Soluble Gums. ODNRI Bulletin No. 2. 108 pp. London: Overseas Development Natural Resources Institute [now Natural Resources Institute, Chatham].

Table 14. Tragacanth: imports into Japan, and sources, 1988-94
(tonnes)
 
  1988  1989  1990  1991  1992  1993  1994 
Total  20  37  31  32 23  33  20 
Of which from :
Iran  12  13  13  13 
Turkey  17  12  15  11  1
UK  11 
Germany 
India 
USA 

Source: National statistics


 

3

SEED GUMS

LOCUST BEAN (CAROB)

DESCRIPTION AND USES

Locust bean (or carob) gum is the whitish powder obtained from grinding the endosperm of the seeds of Ceratonia siliqua, a tree widely cultivated in the Mediterranean region. It consists mainly of galactomannan-type polysaccharides, with a galactose:mannose ratio of about 1:4.

Unlike guar gum (produced from Cyamopsis tetragonoloba), locust bean is only partially soluble in cold water, but it has better water retention characteristics than guar. Solutions of locust bean gum have relatively high viscosities at low concentrations. Dispersions of the gum do not gel well unless it is in combination with other gums. Its strong synergistic action in the presence of other gums contributes to it having wide applications where good stabilizing, thickening and emulsifying properties are required.

Uses of locust bean gum are divided between food and other, miscellaneous applications.

Food use

Its use as a food additive is the most important outlet for locust bean gum. In European Community legislation it has an "E" number of E410. It is employed in a wide range of products, among the most important of which are ice cream, baby foods and pet foods. In these applications its texturizing properties are of great value and hard to replicate using other gums; in ice cream the gum slows the rate of melt-down and improves its storage properties.

Locust bean gum is an important constituent of many soups, where its property of fully dissolving and thickening only at high temperatures is critical. In sausage products such as salami and bologna it acts as a binder and lubricant. Other food uses include the manufacture of soft cheeses, bakery products, pie fillings, powdered desserts, sauces and salad creams, and dairy products other than ice cream.

Miscellaneous applications

The paper industry used to be the biggest consumer of locust bean gum and its derivatives, but its use in this field has diminished considerably. It was added during the paper-making process to improve the physical characteristics of the paper.

In the textile industry, locust bean is used either alone or in combination with starch and synthetics as a sizing agent for cotton and other natural fibres. It is also used as a print-paste thickener in both roller and screen printing to help provide greater purity and uniformity of shades and deeper penetration of dyes.

Other, minor uses include incorporation in oil-drilling fluids, and some pharmaceutical and cosmetics applications.

WORLD SUPPLY AND DEMAND TRENDS

Markets

ROBBINS (1988) details exports and imports for most of the major countries concerned for the years 1979-85, and most of the following discussion draws on his data. Up-to-date information on Japanese imports of locust bean gum, 1988-94, are provided in Table 15.

Robbins estimated total world exports of locust bean gum at about 12 000 tonnes/year. In the period covered by his report, Western Europe was the biggest market (and still is), although substantial quantities are re-exported. Within Europe, the United Kingdom was the biggest importer (averaging about 2 900 tonnes annually), with Germany the next biggest (about 1 700 tonnes/year). The United States' imports averaged 2 300 tonnes/year but were in decline due to prevailing high prices at the time.

Japan is another major market and imported an average of 1 500 tonnes/year during 1979?85. The more recent data given in Table 15 (1988?94) gives an average level of imports of just under 1 700 tonnes/year, not much different to the earlier figure.

At the time of Robbins' report, high prices were posing problems for end-users and there was evidence that locust bean gum was suffering partial substitution by a number of alternatives, notably xanthan gum, carboxy-methylcellulose and modified starches. Since that time, although prices recovered somewhat, they have recently been increasing again; this has been due to a crop shortage in 1994 caused by droughts in the Mediterranean region. In the United States, carrageenan has been making up some of this shortfall.

Supply sources

Estimates over the last 10 years of world production of pods have been in the range 350 000?500 000 tonnes/year. The main gum-producing countries are Spain, Italy and Portugal. Robbins estimated their contributions to the 12 000 tonnes total annual production of locust bean gum to be about 5 000 tonnes, 3 000 tonnes and 1 500 tonnes, respectively. The remaining 2 500 tonnes was accounted for mainly by Morocco, Greece, Cyprus and Algeria. Turkey, Israel, India and Pakistan produce locust bean but were not, then, believed to be significant traders of gum.

Exports of locust bean seed from Cyprus for 1988-92 are shown in Table 16. Apart from the United Kingdom, all other exports from Cyprus go to the three main gum producers, Spain, Italy and Portugal. The level of exports fluctuated but averaged approximately 1 000 tonnes/year.

All the major producers of locust bean gum are shown as recent sources of imports into Japan (Table 15), together with smaller producers such as Greece, India and Morocco, but the data also highlight the extent of re-exports from such countries as Denmark, Netherlands and the United States.

Quality and prices

A number of grades of locust bean gum are available, and for each grade it is possible to have different particle sizes according to the requirements of the end user. The highest grades are in the form of a near-white powder, free from specks of seed hull; particles of seed germ, produced during the primary processing of the seed, are at a minimum. The top grades have the highest viscosity. An average quality gum contains about 12% moisture.

An FAO specification exists for "carob bean gum" employed in foods and this specifies upper limits on such things as moisture content, acid-insoluble matter and protein, as well as arsenic, lead and heavy metals.

An ISO specification also exists but this is for carob pods intended for human consumption, forage or industrial use, and not the seeds or gum.

Current (mid-1995) prices of gum, following a short crop, are very high, in the range US$ 24-30/kg. Prices are expected to fall back to a third of this when the new crop becomes available in September/October.

PLANT SOURCES


Botanical/common names

Family Leguminosae (Caesalpinioideae):

Ceratonia siliqua L. Locust bean, carob, St John's bread

Description and distribution

C. siliqua is a long-lived evergreen tree, up to 15 m tall in favourable conditions in the wild, but under cultivation it is much smaller. It displays great variation in biological form and floral types; in unfavourable habitats it takes a shrubby form with multiple stems. A large number of named cultivars have been developed. The size, shape and thickness of the pod containing the seeds varies greatly depending on the cultivar, but up to 18 hard, brown seeds are contained in each pod; the pod may be up to 30 cm long.

The tree thrives under the hot, dry summers and cool, wet winters of the Mediterranean climate and it is distributed throughout the Mediterranean region. Its cultivation is centred on Spain, Italy and Portugal, but is also undertaken in southern Greece, Turkey, Israel, Lebanon, Syria, Cyprus and other islands in the Mediterranean. More recently, commercial exploitation has developed significantly in several North African countries, including Morocco and Algeria. It has also been introduced to the warmer parts of the United States, Mexico, South Africa, Australia and India.

COLLECTION/PRIMARY PROCESSING

The first commercial fruits can be harvested after about 5-7 years. After flowering, the pods take about 6-8 months to mature, turning from green to chocolate brown in late summer. They are usually harvested by knocking them off with long poles, preferably aimed at the bunches of pods themselves rather than by indiscriminate beating of the branches.

The harvested pods are taken to the kibbling factories where they are left to dry for about a month. They are then crushed and broken in the kibbling machines, which are usually of the hammer mill type, and put through a series of sieves which sorts the broken pieces according to size. The seeds are further separated from pieces of pod of the same size by blowing air through the mixture.

The seeds usually comprise 8-10% of the pod by weight. The approximate composition of the seed (by weight) is:
 

Endosperm  40 - 50% 
Hull  30 - 33% 
Germ  20 - 25% 

Locust bean gum (endosperm) may therefore comprise as much as half of the seed's weight.

The separation of the seed components is a process which requires careful conditioning of the seed prior to fractionation, as well as expensive machinery, and is not always carried out in the country where the pods are harvested. However, because separation of the endosperm constitutes the first stage of gum production, the basic principles of the process are described here, rather than under VALUE-ADDED PROCESSING.

Details of the processing are not public knowledge but the first stage involves removal of the seed hull. This is achieved either by mechanical abrasion or by chemical treatment. In one method, the seeds are roasted, which loosens the hull and enables it to be removed from the rest of the seed; the remaining part is cracked and the crushed germ, which is more friable than the endosperm, is sifted off from the unbroken endosperm halves. An alternative method is to treat the whole seed with acid at an elevated temperature; this carbonizes the hull, which is removed by a washing and brushing operation, and the dried germ/endosperm is then processed as before. Efficient removal of the hull prior to separation of the germ and endosperm is important since residual specks of it will detract from the quality and value of the final product. The pieces of endosperm are then ground to the required particle size to furnish locust bean gum.

Yields

Yields of pods are extremely variable and depend very much on the cultivar in question, as well as climatic and other conditions where the trees are growing. Individual trees have been reported to yield up to 0.5-1.0 tonne of pods but average yields in cultivated stands rarely exceed 2.5 tonnes/ha. Average yields in Cyprus for 1967 (based on 55 000 tonnes production) were equivalent to approximately 2 tonnes/ha or 22 kg/tree. However, another report gives much higher yields: average yields in Cyprus, Israel and Mexico are stated to be equivalent to 10-17 tonnes/ha.

Yields increase steadily up to 25-30 years of age, but may vary in alternate years, being high one year and low the next. Well cared for cultivated trees have a productive life of 80-100 years.

VALUE-ADDED PROCESSING

Further processing involves either chemical modification of the gum or blending with other gums to produce a final product with a range of physical and functional properties designed to suit the end-user's requirements.

PRODUCTS OTHER THAN GUM

Locust bean pods, after grinding into a flour, have traditionally been used as a source of low-grade protein in animal feeds. The pods are especially rich in sugars and are very palatable to cattle and pigs. However, they also contain appreciable amounts of tannins, which reduce digestibility of the protein, and locust bean meal is usually limited to around 10% incorporation in the feed. Germ meal - which is separated from the rest of the seed during gum production - is richer in protein and free of the tannins, and can be used at a higher level of incorporation in feeds, and in all classes of livestock.

The high carbohydrate content of the pod husks enables them to be used for the production of a sugar syrup. Some research has been carried out on the possible use of this syrup as a substrate for microbial protein production. The extracted sugars can also be fermented to alcohol.

In recent years, toasted carob flour produced from the pods has been widely used as a chocolate substitute, particularly in bakery and confectionery products and low calorie snack foods.

DEVELOPMENTAL POTENTIAL

C. siliqua has a number of attributes which make it well suited to promotion as a multipurpose tree in the drier parts of the world. It grows on a wide variety of soils, including marginal and rocky ones, and requires relatively little attention. It is reasonably drought resistant, although it needs some rain if it is to yield commercial quantities of pods. In return, it offers feed (for animals) and, in times of hardship or famine, food for human consumption. It also provides shade and shelter.

If it is intended to develop locust bean as a crop for international trade, rather than local use, then the labour-intensive nature of the harvesting and the increasing costs of labour in southern Europe give some advantages to potential producers in developing countries.

Research needs

If the developmental potential of C. siliqua is to be realized in countries outside its present area of exploitation, then the following research needs must be addressed:

SELECTED BIBLIOGRAPHY

CARLSON, W.A. (1986) The carob: evaluation of trees, pods and kernels. The International Tree Crops Journal, 3, 281-290.

CATARINO, F. (1993) The carob tree - an exemplary plant. Naturopa, 73, 14?15.

CHARALAMBOUS, J. (1966) The Composition and Uses of Carob Bean. Nicosia, Cyprus: Cyprus Agricultural Research Institute.

COIT, J.L. (1951) Carob or St John's bread. Economic Botany, 5, 82-96.

DAVIES, W.N.L. (1970) The carob tree and its importance in the agricultural economy of Cyprus. Economic Botany, 24, 460-470.

DUKE, J.A. (1981) Ceratonia siliqua. pp 50-52. In Handbook of Legumes of World Economic Importance. 345 pp. New York: Plenum Press.

FAO (1992) Carob bean gum [published in FAO Food and Nutrition Paper 49, 1989]. pp 377-380. In Compendium of Food Additive Specifications. FAO Food and Nutrition Paper 52 (Joint FAO/WHO Expert Committee on Food Additives. Combined Specifications from 1st through the 37th Meetings, 1956-1990). Rome: Food and Agriculture Organization.

GRAINGER, A. and WINER, N. (1980) A bibliography of Ceratonia siliqua, the carob tree. The International Tree Crops Journal, 1, 37?47.

HILLS, L.D. (1980) The cultivation of the carob tree (Ceratonia siliqua). The International Tree Crops Journal, 1, 27-36.

ISO (1987) Carob. International Standard ISO 7907-1987. 4 pp. International Organization for Standardization.

NAS (1979) Carob. pp 109?116. In Tropical Legumes: Resources for the Future. 331 pp. Washington, D.C., USA: National Academy of Sciences.

ROBBINS, S.R.J. (1988) Locust bean gum. pp 67-72. In A Review of Recent Trends in Selected Markets for Water-Soluble Gums. ODNRI Bulletin No. 2. 108 pp. London: Overseas Development Natural Resources Institute [now Natural Resources Institute, Chatham].

ROL, F. (1973) Locust bean gum. pp 323-337. In Industrial Gums. Whistler, R.L. (ed.). 810 pp. New York: Academic Press.

SINGH, D. (1961) Get acquainted with the carob. Indian Farming, 11(2), 12 and 40.

WIELINGA, W.C. (1990) Production and applications of seed gums. pp 383-403. In Gums and Stabilisers for the Food Industry, Vol. 5. Proceedings of 5th International Conference, Wrexham, July, 1989. Oxford: IRL Press.

WINER, N. (1980) The potential of the carob (Ceratonia siliqua). The International Tree Crops Journal, 1, 15-26.
 


Table 15. Locust bean gum: imports into Japan, and sources, 1988-94
(tonnes)
  1988  1989  1990  1991  1992  1993  1994 
Total  1720  1531  1686  1781  1524  1573  1899 
Of which from :
Portugal  788  667  725  713  698  472  613 
Denmark  234  225  213  196  201  250  316 
Netherlands  219  206  223  203  205  188  230 
Spain  156  169  226  380  157  325  284 
Italy  128  125  156  146  122  170  243 
USA  95  92  98  91  62  71  93 
Greece  84  41  26  36  69  46  51 
Switzerland  16  18  14  10  20  21 
Germany  28 
India  20 
Morocco  10 
France 

Source: National statistics
 
 

Table 16. Locust bean seeda: exports from Cyprus, and destinations, 1988-92
(tonnes)
  1988  1989  1990  1991  1992 
Total  1578  868  1199  752  466 
Of which to :
UK  na  687  750  409  na 
Italy  na  80  308 184  na 
Spain  na  101  159  na 
Portugal  na  122  na 

Source: National statistics

Note: a Includes decorticated, crushed or ground seed and non-decorticated seed
 


MESQUITE


DESCRIPTION AND USES

The term "mesquite gum" is used here to denote the ground endosperm of the seed from Prosopis spp., in particular P. juliflora, a leguminous tree native to Central America, but now widely distributed elsewhere. An exudate gum, similar in composition to gum arabic, can also be obtained by making incisions into the trunk of the tree, but it is produced in poor yields, and although it has occasionally been offered for sale in North America it is not a widely known item of commerce and is not considered further here.

The ground endosperm of mesquite seed consists mainly of galactomannan-type polysaccharides, similar to those in locust bean and guar gums. Mesquite gum is not yet produced on a commercial scale, but P. juliflora is widely grown as a source of animal feed, fodder and fuel in some countries such as Brazil and India, and since some research has been carried out involving pilot-scale processing of the seed with a view to recovering the gum, it is possible that mesquite may come to be produced commercially in the future.

WORLD SUPPLY AND DEMAND TRENDS

Discussions with members of the gum trade in London have confirmed that mesquite is not a seed gum which is known in Europe. No other information has been found to suggest that it is traded elsewhere.

PLANT SOURCES

Botanical/common names

Family Leguminosae (Mimosoideae): Prosopis spp., especially P. juliflora (Swartz) DC.

Mesquite is a common name applied to several Prosopis species. In South America, the term "algarrobo" (Spanish) or "algaroba" (Portuguese) is used.

The taxonomy of Prosopis is complex and even today the nomenclature used to identify Prosopis species growing in some parts of the world is not consistent.

Description and distribution

Mesquite is a shrubby tree which shows a high degree of genetic diversity in pod size and shape, as well as other features. Various Prosopis species are native to South, Central and North America, Africa and Asia. In addition, several species are widely naturalized outside their native ranges. P. juliflora, for example, is native to Central America but is now very widely distributed, and has colonized large areas of semi-arid wastelands in India, northeast Brazil and elsewhere. In India the species has two distinct forms and occurs either as a single-stemmed tree or a multi-stemmed shrub.

The ability of Prosopis to tolerate severe heat and drought has meant that it has been used to check erosion and the encroachment of desert in arid and semi-arid areas. It has been used for this purpose in Sudan. However, Prosopis is also very invasive, and while this is an advantage when it comes to reforestation of degraded lands, it also poses threats if it gets out of hand. The difficulties in eradicating it, once established, mean that it is a species with opponents as well as proponents as far as its suitability for large-scale planting is concerned.

COLLECTION/PRIMARY PROCESSING

As with other seed gums, the galactomannan component of mesquite seed is contained in the endosperm, which constitutes about 30% of the seed by weight. The seeds themselves are embedded in a hard endocarp and represent about 10% of the pod weight.

A major obstacle to the economic recovery of the seed gum is the toughness of the seed pod and the difficulty, firstly, of separating the seeds from the surrounding pulp and, secondly, splitting and cleanly separating the endosperm from the germ. (One consequence of the hardness of the seed - which contributes to the ability of Prosopis to spread so easily - is that it remains intact during ingestion of the pod by browsing animals and emerges later in a suitable state for germination).

Yields

Yields of 10 tonnes/ha of pods have been reported from cultivated mesquite in Brazil, equivalent to a yield of about 1 tonne/ha of seeds or 300 kg/ha of gum (endosperm). Elsewhere, 2.3 tonnes/ha/year of pods have been reported from a density of 118 trees/ha, equivalent to a yield of about 20 kg/tree.

PRODUCTS OTHER THAN GUM

Since ancient times, Prosopis has been used in the Americas as a source of food, fodder and fuel. The pods are high in fibre and the seeds are rich in protein, although the full nutritional value is only gained if they are ground to make a flour. The sweetish pulp surrounding the seeds makes the pods relished by browsing animals. The proliferation of flowers which are produced by Prosopis makes them attractive to bees, thus supporting honey production.

In several countries where mesquite is grown the tree is a valuable source of fuelwood ? in the arid tract of Rajasthan in India up to 70% of the fuelwood demand is met by mesquite. The wood has a high calorific value and, since the plant also coppices well when cut, the one-year old coppice regrowth is frequently cut and used to make charcoal.

Prosopis timber is generally very hard and durable and it has been used for such things as railway sleepers and parquet flooring, and in joinery; the poor stem form of the tree does not make it suitable for large timber applications.

DEVELOPMENTAL POTENTIAL

There would be several benefits to accrue from the use of mesquite for seed gum production. It would give those farmers who presently grow it as a means of providing protein to livestock an alternative source of cash income from the same crop. And in those regions where "wild" Prosopis grows extensively as part of soil conservation measures (and might be used as a source of fuelwood or charcoal by local people) there would be similar opportunities for income generation.

However, the risks associated with the introduction of mesquite have been referred to earlier and they should not be underestimated. Great care should be exercised in any research that entails planting mesquite in new areas.

Research needs

The most pressing practical problem to be overcome is that of separating the seed from the pod and obtaining reasonably pure endosperm from the seed. If this was to be done with the aim of producing gum for the international market it would have to be achieved at a cost which compares favourably with locust bean or guar, but still gives the farmer an adequate economic return. For a farmer who presently grows mesquite as a source of animal feed, the economics of gum production still need to be favourable enough to divert him from feed to gum.

The research needs should therefore include:

SELECTED BIBLIOGRAPHY

BURKART, A. (1976) A monograph of the genus Prosopis (Leguminosae Subfam. Mimosoideae). Journal of the Arnold Arboretum, 57, 219-249 and 450-525.

CESPEDES-ROSSEL, R. (1985) [Extraction of Gum from Mesquite Seeds] (in Spanish). 167 pp. Lima, Peru: Facultad de Industrias Alimentarias, Universidad Nacional Agraria.

DEL VALLE, F.R., ESCOBEDO, M., MUNOZ, M.J., ORTEGA, R. and BOURGES, H. (1983) Chemical and nutritional studies on mesquite beans (Prosopis juliflora). Journal of Food Science, 48(3), 914-919.

DUTTON, R.W. (ed.) (1992) Prosopis Species. Aspects of their Value, Research and Development. Proceedings of Prosopis Symposium, University of Durham, UK, 27-31 July, 1992. 320 pp.

FAGG, C.W. and STEWART, J.L. (1994) The value of Acacia and Prosopis in arid and semi-arid environments. Journal of Arid Environments, 27, 325.

FIGUEIREDO, A.A. (1983) [Extraction, identification and characteristics of the polysaccharides of algarobeira seeds (Prosopis juliflora DC.)] (in Portuguese). Ciencia e Tecnologia de Alimentos, 3(1), 82.

FIGUEIREDO, A.A. (1987) [Industrialization of the pods of algaroba (Prosopis juliflora) aimed at the production of seed gum] (in Portuguese). Revista Associacao Brasileira de Algaroba, 1(1), 7.

FIGUEIREDO, A.A. (1990) Mesquite: history, composition and food uses. Food Technology, 44(11), 118-128.

MEYER, D., BECKER, R. and NEUKOM, H. (1982) Milling and separation of Prosopis pod components and their application in food products. In Proceedings of the Symposium on Mesquite Utilization, Texas Technical University, Lubbock, Texas.

NAS (1979) Prosopis species. pp 153?163. In Tropical Legumes: Resources for the Future. 331 pp. Washington, D.C., USA: National Academy of Sciences.

SAXENA, S.K. and VENKATESWARLU,J. (1991) Mesquite: an ideal tree for desert reclamation and fuelwood production. Indian Farming, 41(7), 15-21.
 
 


TARA

DESCRIPTION AND USES

Tara gum constitutes the clean, ground endosperm of the seeds of Caesalpinia spinosa. It is a white to yellowish white powder and consists chiefly of galactomannan-type polysaccharides. The ratio of galactose to mannose in tara gum is 1:3 (compared to 1:4 in locust bean gum and 1:2 in guar gum).

Tara gum is used as a thickening agent and stabilizer in a number of food applications. A solution of it is less viscous than a guar gum solution of the same concentration, but more viscous than a solution of locust bean gum. Blends of tara with modified and unmodified starches can be produced which have enhanced stabilization and emulsification properties, and these are used to advantage in the preparation of convenience foods.

WORLD SUPPLY AND DEMAND TRENDS

Markets

Tara gum is a relative newcomer to international trade and developmental work aimed at exploring the range of applications for which it might be suitable is still being undertaken.

Peru is the major exporter of powdered tara pods, which are used as a source of tannin (see PRODUCTS OTHER THAN GUM below), but data on tara gum are not readily available. A recent estimate of 1 000 tonnes annually was given by WIELINGA (1990) for total world production of tara gum, but no indication was given either of the trend or of the main markets.

Supply sources

Peru, as stated above, is believed to be the biggest (and, perhaps, the sole) exporter of tara gum. Bolivia and Ecuador are known to harvest small quantities of tara and there may be some production, also, in Chile and Colombia.

Quality and prices

The highest grades of tara gum are white and free from specks of husk and germ.

An FAO specification exists for tara gum which specifies upper limits on parameters such as moisture, ash, acid-insoluble matter, arsenic, heavy metals and protein.

Prices for tara gum are not known.

PLANT SOURCES

Botanical/common names

Family Leguminosae (Caesalpinioideae):

Caesalpinia spinosa L. Tara, huarango

Description and distribution

C. spinosa is a shrub or tree, with spreading, grey-barked leafy branches. The pods are flat, about 10 cm long and 2.5 cm wide, containing 4-7 large round seeds; the seeds are black when mature.

The tree is native to the Cordillera region of Bolivia, Peru and northern Chile and also occurs in Ecuador, Colombia, Venezuela and Cuba. It is also cultivated in most of these countries. It has been introduced to other parts of the world, including North Africa (notably Morocco) and East Africa.

It grows in ecological zones ranging from Warm Temperate Dry through Tropical Very Dry to Tropical Wet forest zones.

COLLECTION/PRIMARY PROCESSING

No easily accessible information is available on the harvesting of tara or on yields of seed to be expected from the tree. Most seed is harvested from wild trees although these are subjected to simple pruning operations.

The physical composition of tara seed (by weight) is approximately:
 

Germ  40% 
Hull  38% 
Endosperm  22% 

Yields of tara gum (endosperm) from the seed are therefore relatively small (22%), and less than that for the two other principal seed gums, locust bean (40-50%) and guar (ca 35%).

Like locust bean, the hull of tara is tough and hard, and special processes have to be used to remove the hull before separating the endosperm and germ. Acid treatment or roasting processes (as described for locust bean) are used to obtain the endosperm.

VALUE-ADDED PROCESSING

Like guar gum, further processing entails blending tara with other gums or chemically modifying it to produce the range of functional properties that are sought. This further processing is capital-intensive and is only carried out on a large scale by companies who process other gums in a similar manner.

PRODUCTS OTHER THAN GUM

Once separated from the hull and endosperm, it should be possible to use the germ of the seed as a source of protein, perhaps in animal feeds. However, it is not known whether this occurs in practice.

Tara pods are rich in tannin and are a regular item of trade in Peru for tanning purposes. The tannin is used extensively in South America and Morocco for tanning sheep and goat skins, and produces a good quality, light-coloured leather. Peruvian exports of powdered tara for tanning purposes averaged just over 5 000 tonnes/year during 1990-93.

C. spinosa is sometimes grown as a live fence in Peru for keeping out animals.

DEVELOPMENTAL POTENTIAL

There is very little documented information available to know to what extent tara has been investigated as a dual purpose seed crop. Since the pods are utilized for tannin extraction purposes it is logical to think, also, in terms of gum production from the seeds. In this way, further economic value can be derived from a single harvested product (i.e., pods containing the seeds).

The opportunities for increasing production of tara depend very much on the markets for both tara gum and the tannins derived from the pods. If both markets are supplied from present production, then a disproportionate upturn in one market will, if met by increased production, cause an oversupply in the other. The greatest need in ascertaining the developmental potential of tara is therefore to investigate the markets for the seed (as a source of gum) and the pods (as a source of tannin).

SELECTED BIBLIOGRAPHY

BENK, E. (1977) [Tara kernel meal. A new thickening, binding and stabilizing agent] (in German). Riechstoffe, Aromen, Kosmetica, 27(10), 275-276.

DUKE, J.A. (1981) Caesalpinia spinosa. pp 32?33. In Handbook of Legumes of World Economic Importance. 345 pp. New York: Plenum Press.

FAO (1992) Tara gum [published in FAO Food and Nutrition Paper 37, 1986]. pp 1475-1476. In Compendium of Food Additive Specifications. FAO Food and Nutrition Paper 52 (Joint FAO/WHO Expert Committee on Food Additives. Combined Specifications from 1st through the 37th Meetings, 1956-1990). Rome: Food and Agriculture Organization.

JUD, B. and LOESSL, U. (1986) [Tara gum - a thickening agent with a future] (in German). Internationale Zeitschrift fur Lebensmittel Technologie und Verfahrenstechnik, 37(1), 28-30.

ROJAS-PAJARES, H. (1991) [Determination of Parameters for Obtaining Tara Seed Gum (Caesalpinia tinctorea) by Aqueous Method and Dried by Spray Drying] (in Spanish). 94 pp. Lima, Peru: Universidade Nacional Agraria La Molina (Escuela de Post-Grado, Especialidad de Tecnologia de Alimentos).

RUIZ, C.A.B. (1994) Country paper: Peru. Paper presented at the FAO Expert Consultation Meeting on Non-Wood Forest Products, Santiago, Chile, 4-8 July.

WIELINGA, W.C. (1990) Production and applications of seed gums. pp 383-403. In Gums and Stabilisers for the Food Industry, Vol. 5. Proceedings of 5th International Conference, Wrexham, July, 1989. Oxford: IRL Press.


4

HARD RESINS

 

COPAL

DESCRIPTION AND USES

The term copal applies to a large group of resins characterized by their hardness and relatively high melting point. They are soluble in alcohol. Up until the 1940s, or thereabouts, they were among the best of the natural resins for use in varnish and paint manufacture, and traded in very large volumes. In the oil-soluble form they were also used in the manufacture of linoleum. Copal has been produced from a large number of different tree species from many parts of the world - Africa, Asia and South America. Today, most copal of commerce originates from Agathis species of Southeast Asia: the Malay and Indonesian archipelagos in particular and, to a lesser extent, the Philippines.

Today, the major use of copal is as a varnish for wood and paper. It still finds use in road-marking paints, where the capacity of the resin to prevent bleed-through of road-making materials is beneficial, and there are numerous other, minor uses.

Until the decline in demand for copals brought about by the use of synthetic resins for varnish and paint manufacture, much of the copal was collected in the fossilized or semi-fossilized form. Nowadays, most of it is collected by tapping the living tree. Furthermore, many of the trees which are now tapped have been planted, and there is no longer dependence on the wild forest.

Historical introduction

Historically, the copals have been classified according to their geographical origin:

Apart from brief reference to the botanical sources of the African and South American copals (Plant Sources), the rest of the discussion below is confined to those copals which are still produced today: copal of mainly Indonesian origin and Manila copal ("almaciga"). Both are produced from Agathis species.

WORLD SUPPLY AND DEMAND TRENDS

Markets

Exports of copal from Indonesia and the Philippines for the period 1988-93, and their destinations, are given in Tables 17 and 18, respectively.

Total exports from Indonesia and the Philippines averaged about 2 300 tonnes annually during 1988-93. Most Indonesian copal (and some Filipino) is shipped via Singapore but Germany, which also imports directly from Indonesia, is a major onward destination and the most important in Europe. India and Japan import modest quantities directly from Indonesia. China (Taiwan) is the biggest importer of copal from the Philippines.

Imports of copal and damar into Japan during 1985-87 are shown in Table 19, although it is not possible to separate the two commodities. After 1987, copal and damar are not separated from "Natural gums, resins, gum-resins and balsams, n.e.s.". Combined imports of copal and damar averaged just over 400 tonnes/year in 1985-87.

Photo N.5 :Cleaning and sorting copal, Java, Indonesia. (Photo: J.J.W. Coppen)

Supply sources

Indonesia is by far the biggest producer and exporter of copal. After the fall in exports in 1989 from almost 2 500 tonnes the previous year (Table 17), levels have been remarkably constant at about 1 850 tonnes/year.

The Philippines is the second biggest producer of copal; exports during 1988?93 averaged about 350 tonnes/year with no clear trend.

In 1982, Sarawak exported just over 50 tonnes of copal; Malaysian exports since then record only very small quantities of copal.

Papua New Guinea has been a small producer and exporter in the past but the present scale of production from this source (if any), and other islands of the Pacific, is not known.

Quality and prices

The quality of copal which is collected is very variable, depending inherently on the species from which it is obtained (which may affect its solubility properties) and the manner in which it is collected: whether by tapping or by picking from the ground in a fossilized form. After cleaning (removing pieces of bark and other foreign matter), different grades of copal in trade are distinguished by their hardness, colour and size of the pieces, as well as the state of cleanliness. Pale, clean pieces, with good solubility in alcohol, are the best quality.

Present (mid-1995), indicative prices for some Indonesian copal grades shipped from Singapore (CIF London) are:
 

"Clean scraped chips" 

US$ 1 500/tonne 

"Medium scraped chips" 

US$ 1 000/tonne 

"Small chips" 

US$ 900/tonne 

Prices have been fairly stable in recent years.
 

PLANT SOURCES


Botanical names (present day Asia/Pacific copals)

Family Araucariaceae: Agathis spp.

The taxonomy of Agathis has been, and still is, confused and in the past, numerous different species names have been cited as the source of copal; the most common one has been A. alba. In some cases, even now, plantation trees, grown and tapped in Indonesia, are referred to simply as "Agathis spp.", with no attempt to give a full name.

WHITMORE (1977, 1980) and de LAUBENFELS (1989) recognize more than a dozen species of Agathis - which extend from peninsular Malaysia, across the Malay and Indonesian archipelagos to islands in the Pacific (as far east as Fiji), and south to the coastal regions of Queensland, Australia, and New Zealand - although the authors differ on some points. They agree that the natural stands on Peninsular Malaysia, Sumatra and Borneo which are sources of copal are those which should be designated A. borneensis Warb., but trees in the Philippines and Sulawesi are considered to be A. dammara (Lamb.) Richard by Whitmore and A. philippinensis Warb./A. celebica (Koord.) Warb. by de Laubenfels. Other copal producers include A. labillardieri Warb.

The identity of the extensive plantation Agathis which are tapped on Java is not known (to the present author) and to avoid confusion no species name is attached to Agathis hereafter in this discussion.

Historical copals

(N.B. The genera given below all belong to the family Leguminosae. However, the species listed are those attributed by HOWES (1949); their current acceptance in terms of botanical nomenclature is not known and some of the names may be obsolete.)

Congo copal

Mainly or entirely from Copaifera demeusei.

West African copals

Copaifera copallifera, C. demeusei, C. mopane.

East African copal

Almost entirely from Trachylobium verrucosum.

South American copals

Various Hymenaea spp., especially H. courbaril L.

Description and distribution (Asia/Pacific copals)

Agathis is the most tropical of all conifers. The copal-yielding species are very tall trees, up to 60 m high, often with a near-cylindrical bole. However, there can be some variation in the characters of the living tree, as well as the ecological conditions under which it occurs. It is grown widely as a timber tree on Java (over 100 000 ha) and other parts of Indonesia.

The distribution of Agathis has been discussed above.

COLLECTION/PRIMARY PROCESSING

Nowadays, most copal, at least that intended for international markets, is obtained by tapping the tree, rather than collecting fossilized resin from the ground. In the tree, the resin resides in the living inner bark of the trunk and tapping involves making incisions into the bark and collecting the exudate. Fresh cuts are made at suitable intervals - a few days or a week or more - gradually moving up the tree. The size and shape of the cuts, the extent to which they might penetrate the wood, and their frequency of application have changed over the years and still vary according to the country or region in which tapping is undertaken, or the traditions of the communities involved.

Present practice on Java is for the tapper to return to the tree to make fresh incisions every 3?4 days; up to four or more small tin cups may be in place at different points on the tree at any one time, depending on the size of the tree. In the Philippines, research has been undertaken using tapping methods very similar to those used in tapping pine trees (involving use of sulphuric acid as a chemical stimulant), but it is not known whether such methods are used commercially.

Collected resin is cleaned by sieving and hand picking to remove foreign matter, and packed in sacks for transfer to points of sale, either nationally or internationally.

Yields

Resin yields are very variable and depend on a large number of factors: genetic, environmental and practical (i.e., method of tapping used). Annual yields of 16-20 kg have been reported from good trees in the Philippines and Papua New Guinea, while average yields have been variously estimated at 2 kg or as much as 10-12 kg. Recent tapping trials at three sites in the Philippines resulted in average annual yields of 1.2 kg, 3.7 kg and 5.6 kg/tree.

Recent research in Indonesia and the Philippines has shown that thick-barked Agathis yields significantly more resin than thin-barked trees (in one study in Indonesia, almost nine times as much), and that tapping in the morning and at the side of the tree which maximizes the length of time that sunlight falls on it is beneficial to resin yields.

VALUE-ADDED PROCESSING

No further processing is carried out until the copal is formulated for use by the end-user; this may involve heat treatment, dissolution in a suitable solvent and/or chemical processing. The latter may be carried out by a specialist chemical processor and usually involves preparation of copal esters to neutralize the natural acidity of copal and render it oil-soluble.

PRODUCTS OTHER THAN RESIN

Agathis produces a high class, much valued, utility timber and it is grown widely as a timber tree. In Malaysia, it is the most important commercial softwood, and it is also widely planted in Indonesia.

DEVELOPMENTAL POTENTIAL

Resin-yielding Agathis are planted for timber, rather than as a source of resin, and tapping of plantation trees is therefore a secondary activity to that of timber production. The proportion of planted trees which are tapped commercially is not known, but it is probable that it is a relatively small proportion and that copal production from such sources could be increased significantly if demand and the economics of production were favourable.

By nature, the trees are very large and there is little scope for agroforestry-type interventions. However, taking into account the fact that there is a steady demand for copal, that some copal will continue to be obtained from wild sources, and that importers are always prepared to consider new, reliable sources of supply, there may be some opportunities for new producers - perhaps for some of the Pacific islands where cooperatives can be organized.

SELECTED BIBLIOGRAPHY

ANON. (1962) Almaciga Resin. FPRI Technical Note No. 35. 4pp. Laguna, the Philippines: Forest Products Research and Industries Development Commission.

BILLING, H.J. (1944) Congo Copal. The Oil and Colour Trades Journal, 3(Nov), 666-668.

BOWEN, M.R. and WHITMORE, T.C. (1980) The tropical conifer Agathis as a potential plantation tree. Paper presented at IUFRO Symposium and Workshop on Genetic Improvement and Productivity of Fast-growing Tree Species, Sao Paulo, Brazil, August 1980.

BOWEN, M.R. and WHITMORE, T.C. (1980) A Second Look at Agathis. Occasional Paper No. 13. 19 pp. Oxford: Commonwealth [now Oxford] Forestry Institute, University of Oxford.

CONELLY, W.T. (1985) Copal and rattan collecting in the Philippines. Economic Botany, 39(1), 39-46.

GONZALES, E.V. and ABEJO, F.G. (1978) Properties of Manila copal (almaciga) resin from 15 different localities in the Philippines. Forpride Digest, 7(1), 68-69.

GONZALES, L.L., CRUZ, V.C. and URIARTE, M.T. (1986) Effects of seasonal variation and sulphuric acid treatment on the resin yield of almaciga (Manila copal). Sylvatrop, 11(1-2), 43-54.

HALOS, S.C. (1983) Factors affecting quality and quantity of almaciga resin. National Research Council of the Philippines Research Bulletin, 38(1), 70-113.

HARRISON-SMITH (1941) Kauri gum. New Zealand Journal of Forestry, 4, 284-292.

HOWES, F.N. (1949) The copals. pp 93-103. In Vegetable Gums and Resins. 188 pp. Waltham, USA: Chronica Botanica.

De LAUBENFELS, D.J. (1989) Agathis. pp 429-442. In Flora Malesiana, Series I, Vol. 10. Dordrecht, The Netherlands: Kluwer Academic Publishers.

ORDINARIO, F.F. and TONGACAN, A.L. (1979) The influence of diameter and sulphuric acid on the resin yield of almaciga (Agathis philippinensis Warb.). Forpride Digest, 8(2), 21-34.

RIYANTO, T.W. (1980) [Small notes on copal resin] (in Indonesian). Duta Rimba, 6(42), 23-28.

SAULEI, S.M. and ARUGA, J.A. (1994) The status and prospects of non-timber forest products development in Papua New Guinea. Commonwealth Forestry Review, 73(2), 97-105.

SOENARNO, M.M.I. (1987) Copal production on Agathis spp of varying bark thicknesses, West Java. Duta Rimba, 13(Mar/Apr), 3-6.

SOENARNO, M.M.I. and BASARI, Z. (1984) [Study on the improvement of copal tapping procedure at Sukabumi Forest District, Java, Indonesia] (in Indonesian). Jurnal Penelitian Hasil Hutan, 1(3), 34-38.

SUMANTRI, I. (1991) [Relation between tree diameter and copal production during tapping of Agathis spp] (in Indonesian). Duta Rimba, 17(135-136), 42-45.

SUMANTRI, I. and DULSALAM (1991) [Manipulation of tapping design to increase resin yield of Agathis] (in Indonesian). Jurnal Penelitian Hasil Hutan, 9(1), 1-4.

SUMANTRI, I. and SASTRODIMEDJO, S. (1976) [Tapping Trials of Agathis Hamii M. Dr. in South Sulawesi] (in Indonesian, English summary). Report No. 58. Bogor, Indonesia: Forest Products Research Institute.

TONGACAN, A.L. and ORDINARIO, F.F. (1974) Tapping of almaciga resin. The Philippine Lumberman, 20(12), 18-19, 22-23, 25.

WHITMORE, T.C. (1977) A First Look at Agathis. Tropical Forestry Paper No. 11. 54pp. Oxford: Commonwealth [now Oxford] Forestry Institute, University of Oxford.

WHITMORE, T.C. (1980) Utilization, potential and conservation of Agathis, a genus of tropical Asian conifers. Economic Botany, 34(1), 1-12.

WHITMORE, T.C. (1980) A monograph of Agathis. Plant Systematics and Evolution, 135, 41-69.

Table 17. Copal: exports from Indonesia, and destinations, 1988?93
(tonnes)

 

1988 

1989 

1990 

1991 

1992 

1993 

Total 

2485 

1811 

1766 

1880 

1863 

1886 

Of which to :

Singapore 

1807 

1233 

1130 

1173 

1332 

1362 

Germany 

262 

405 

435 

495 

390

258 

India 

38 

45 

90 

105 

15 

57 

Japan 

38 

60 

38 

63 

25 

25 

Hong Kong 

22 

51 

30 

14 

30 

83 

China (Taiwan) 

270 

15 

Pakistan 

28 

30 

71 

87 

UK 

45 

Netherlands 

17 

France 

14 

Source: National statistics
 
 
 

Table 18. Manila copal: exports from the Philippines, and destinations, 1988-93
(tonnes)

 

1988

1989 

1990 

1991 

1992 

1993 

Total 

407 

345 

288 

363 

272 

382 

Of which to :

China (Taiwan) 

184 

196 

139 

224 

171 

286 

Hong Kong 

91 

72 

78 

84 

60 

52 

Singapore 

70 

57 

60 

44 

30 

USA 

56 

20 

14 

France 

11 

Germany 

11 

30 

Source: National statistics
 
 

Table 19. Copal and damar: imports into Japan, and sources, 1985-87
(tonnes)

 

1985 

1986 

1987 

Total 

441 

441 

347 

Of which to :

Indonesia 

426 

414 

347 

Singapore 

15 

27 

15 

Malaysia 

30 

Source: National statistics


 

DAMAR

DESCRIPTION AND USES

"Damar" (sometimes spelled dammar) is a Malay word meaning resin or torch made from resin. Although, today, the word is used in a more restrictive sense, it is still applied as a collective term to a great variety of hard resins. Damars of international commerce come from the dipterocarp forests of Southeast Asia, mainly from Indonesia. Damar from the sal tree is produced in India. Production is mainly by tapping living trees, although some is still collected from the ground in fossilized form.

Damars are solid resins, generally less hard and durable than the copals, and white to yellow in colour. They are distinguished from copal by their solubility in hydrocarbon-type solvents and drying oils. Like copals, however, their main use is still in the manufacture of paper or wood varnishes and lacquers, and some paints, although consumption has inevitably declined over the years with the widespread use of synthetic materials. They used to be an important ingredient in many types of cellulose lacquers, imparting gloss and adhesive qualities and preventing after-yellowing. Nowadays, they find particular use as a varnish for the fine arts.

Miscellaneous minor uses include the manufacture of inks, polishes, water-resistant coatings and injection moulding materials. A little is used in foods as a clouding or glazing agent. In the countries where damars are produced, they find local use for caulking boats and baskets. In India, sal damar is widely used as an incense and in the indigenous system of medicine.

WORLD SUPPLY AND DEMAND TRENDS

Markets

Interpretation of trade statistics for damar is made more hazardous than usual by the use of different terms for resins which are, nevertheless, damars of one type or another. Examination of Indonesian trade statistics reveals three different damars: "Gum damar", "Mata kucing" and "Batu". Mata kucing ("cat's eye") is a term applied to the crystalline damar resin (usually in the form of round balls) obtained from certain of the dipterocarp species. Batu ("stone") refers to the opaque, stone or pebble-shaped damar collected from the ground.

Indonesian exports of the three types of damar for 1988-93, and their destinations, are given in Tables 20a, 20b and 20c. Average annual exports have been approximately 2 000 tonnes (gum damar), 6 300 tonnes (Batu) and 3 200 tonnes (Mata kucing), making about 11 500 tonnes in total. There is some year-to-year fluctuation, but nothing that indicates a downward trend.

Exports of damar from Thailand for the period 1988-93, and destinations, are shown in Table 21. Exports have averaged approximately 1 800 tonnes/year, with a slight downward trend.

Considering Indonesian and Thai exports with smaller amounts from other countries, total international trade in damar might approach 15 000 tonnes/year.

Most Indonesian damar is exported to Singapore from where it is re-exported to consumer countries. Of those other countries which import directly from Indonesia, Germany is a major destination, particularly of batu (taking about 2 000 tonnes in each of 1992 and 1993). Other Southeast Asian countries such as China (Taiwan) and Malaysia import significant quantities, as does India. India is the biggest market for Thai damar and in recent years has taken all, or almost all, of Thailand's exports, around 1 500-2 000 tonnes/year.

Except for 1989, Japanese imports have been limited to "gum damar", usually about 100-140 tonnes annually. Combined imports of copal and damar for 1985-87 have been given earlier (Table 19).

Indian consumption of damar from indigenous sources is believed to be substantial but cannot be quantified.

Photo N.6 : A damar (Shorea javaica) garden in southern Sumatra, Indonesia, First
cuts for tapping are made when the tree is about 20 years old. (Photo: Mien Kaomini)

Photo N.7 :Tapper climbs the tree supported by a rattan belt to collect the solidified
exudated (damar) and to refresh the cuts, Sumatra, Indonesia. ( Photo: H. de Foresta)

Supply sources

Indonesia is by far the major source of internationally traded damar. Export statistics are not easily accessible for some of the other countries known to produce damar, but of these, Viet Nam, Laos and Cambodia have exported variable quantities. De BEER (1993) has estimated Laotian production of damar at 500-1 000 tonnes/year and states that most is exported to Thailand; a proportion of Thai exports may therefore simply be re-exports of damar from Laos. Malaysia exports small quantities of damar but the larger level of imports make it a net importer.

Quality and prices

As would be expected for a commodity of such diverse origins, damar is of extremely variable quality. Colours range from very pale grades to those which are grey-black. Physical form and size varies from large irregular lumps or smaller globular lumps to small chips and dust. In past years, damars of recognized quality were usually identified by the port at which cleaning and grading took place and from where they were dispatched, or their geographical origin (e.g., Pontianak and Batavia), and this is still often the case today (e.g., Palembang).

There is an FAO specification for damar which gives a number of limits for such things as arsenic, lead and heavy metal content.

Illustrative of current (mid?1995) prices (CIF London) are the following for grades A-C of Palembang damar:
 

US$ 1 250 - 1 370/tonne 

US$ 1 225 - 1 345/tonne 

US$ 1 120 - 1 215/tonne 

The lower end of each range is the discounted price for larger (container load) lots. Dealers in London state that prices have been very stable over recent years.

PLANT SOURCES


Botanical names

Family Dipterocarpaceae:

Shorea spp. (including S. javanica K. & V. [Sumatra], S. lamellata Foxw. [Malaysia, Sumatra, Borneo], S. virescens Parijs [Borneo, the Philippines], S. retinodes Sloot. [Sumatra], S. guiso (Blco) Bl. [Thailand, Malaysia, Sumatra, Borneo, the Philippines] and S. robusta Gaertn. f. [India]).

Hopea spp. (including H. dryobalanoides Miq. [Malaysia, Sumatra, Borneo] and H. celebica Burck. [Sulawesi]).

Vatica spp. (including V. rassak (Korth.) Bl. [Borneo, the Philippines, Sulawesi, New Guinea]).

Vateria spp.

Balanocarpus spp.

Family Burseraceae: Canarium spp.

Description and distribution

Trees of the family Dipterocarpaceae are medium to very large trees, widespread and of very great importance as a source of tropical hardwood throughout the Indian and Southeast Asian regions, including the Malay and Indonesian archipelagos. A large number of species from several genera have been tapped for resin at one time or another, and where the resin which is collected is used locally this is still probably true. The number of species which yield resin which eventually enters world trade is smaller but the identity of the botanical source is usually lost as the damar passes through the various stages of sale.

Shorea robusta is tapped in India. Wild trees of various Shorea and Hopea species are tapped in Myanmar, Thailand, Laos, Cambodia and Viet Nam. Although many dipterocarps flower and fruit very irregularly (which has hampered attempts to cultivate them) damar is collected from certain species which have been successfully planted by local people in Indonesia: S. javanica and H. dryobalanoides in Sumatra and Vatica rassak in Kalimantan, Sulawesi and Maluku.

Canarium spp. also yield a dammar-type resin, which is occasionally collected although it is not believed to be an important item of commerce.

COLLECTION/PRIMARY PROCESSING

TORQUEBIAU (1984) gives a good description of tapping cultivated S. javanica in Sumatra. Traditional methods of tapping trees to obtain damar (whether wild or cultivated trees) involve removal of wood from the stem. Cuts made into the trunk have a triangular form but become circular with age and are arranged in vertical rows around the trunk. The first cuts are made when the tree is approximately 25 cm in diameter (about 20 years old). The cut is several centimetres wide at first, but becomes enlarged at every tapping and eventually becomes a hole of 15?20 cm in depth and width. The average number of holes for a tree about 30 m high and 60?80 cm diameter is 9?11 in each of 4?5 vertical rows. For the higher holes, the tapper climbs the tree supported by a rattan belt and using the lower holes as footholds.

The exuded resin is allowed to dry on the tree before it is collected; resin which forms hard drops becomes "mata kucing". The frequency with which the tree is visited to refreshen the cut varies from once a week to once a month, depending on how far the tree is from the village. Tapping can continue for 30 years.

In India, tapping involves removing narrow strips of bark from the tree. The resin which exudes solidifies and darkens on drying and is then removed from the tree. Tapping is repeated several times a year.

Yields

When tapped once a month in the manner described above, a fully productive tree has been stated to yield about 4 kg of damar at each tapping, i.e., about 48 kg/year. However, there is known to be genotypic (tree-to-tree) variation in yields and some trees may only be tapped every 3 months because of poor yields. In other cases, if the resin from a good-yielding tree is not collected for 6 months it may completely fill the hole in the tree (10-15 cm wide and deep).

Resin production is reported to fall markedly when the tree is flowering and fruiting, and only reaches previous levels a year later.

Photo N.8 : A Shorea Javanica tree in later stages of tapping, Sumatra, Indonesia
Tapping continues for a period of about 30 years. ( Photo: Mien Kaomini)
 

VALUE-ADDED PROCESSING

So-called "dewaxed" damar is prepared by dissolving damar in a hydrocarbon solvent and precipitating and removing a high-melting, resinous fraction. The remaining soluble fraction is then more compatible with the cellulose component of cellulose lacquers.

PRODUCTS OTHER THAN RESIN

Damar-producing trees are also highly valued for timber, and felling them for sawtimber or the manufacture of value-added wood products is usually the primary activity. Some local use is made of the fruits.

In India, an oil is distilled from the resin which is used for fragrance and medicinal purposes. The seeds of sal furnish a fatty oil and the residual cake can be used as an animal feed.

DEVELOPMENTAL POTENTIAL

The "kebun damar" (damar gardens) of S. javanica in Lampung, southern Sumatra, are an example of how, over many years, communities have developed a traditional cultivation system which is now regarded as a model of agroforestry technique. Rain-fed rice is grown for one or two years and then coffee, pepper or some other crop is planted, together with Shorea and other useful trees such as cloves. While the damar trees are reaching the age at which they can first be tapped (15-20 years), other products can be harvested to provide cash income to the farmers. The whole system converts one of a shifting cultivation to a permanent, sustainable, productive land-use system.

Much is still to be learnt about the biology and silviculture of S. javanica but valuable knowledge and experience has already been gained and research is still in progress through BIOTROP in Bogor, Indonesia. It is hoped that the successful development of plantations of S. javanica will encourage the use of other dipterocarps and native trees for plantation forestry. There is much potential, therefore, for the agroforestry approach to damar production, not only in Indonesia but in other countries, and the important question may then be that of the market and how much damar it can absorb.

Research needs

Apart from the need to acquire more detailed information on the markets for damar (countries or regions which are important consumers, end uses, customer requirements in terms of quality, etc.), other areas of research (in addition to continued research on silvicultural aspects) should include:

SELECTED BIBLIOGRAPHY

ANON. (1959) Dewaxed damar - a review. Paint, Oil and Colour Journal, 11(Sep), 215-218.

ANON. (1973) Damar. FPRI Technical Note No. 136. 3pp. Laguna, the Philippines: Forest Products Research and Industries Development Commission.

De FORESTA, H. and MICHON, G. (1994) Agroforests in Sumatra - where ecology meets economy. Agroforestry Today, 6(4), 12?13.

FAO (1992) Dammar gum [published in FAO Food and Nutrition Paper 31/2, 1984]. p 475. In Compendium of Food Additive Specifications. FAO Food and Nutrition Paper 52 (Joint FAO/WHO Expert Committee on Food Additives. Combined Specifications from 1st through the 37th Meetings, 1956-1990). Rome: Food and Agriculture Organization.

GIANNO, R. (1986) The exploitation of resinous products in a lowland Malayan forest. Wallaceana, (43), 3-6.

JAFARSIDIK, J. (1987) [Damar resin-producing tree species and their distribution in Indonesia] (in Indonesian, English summary). Duta Rimba, 13(Mar/Apr), 7-11.

JAFARSIDIK, Y.S. (1982) [Resin-producing tree species in Sumatra] (in Indonesian, English summary). Duta Rimba, 8(54), 36-37.

MESSER, A.C. (1990) Traditional and chemical techniques for stimulation of Shorea javanica (Dipterocarpaceae) resin exudation in Sumatra. Economic Botany, 44(4), 463-469.

SOESILOTOMO, P.S. (1992) [Damar tree breeding [for increased resin production] in Probolinggo Forest District] (in Indonesian). Duta Rimba, 18(143), 42-46.

TORQUEBIAU, E.F. (1984) Man-made dipterocarp forest in Sumatra [including Shorea javanica tapped for resin]. Agroforestry Systems, 2(2), 103-127.

TORQUEBIAU, E.F. (1987) Multidisciplinary research on Shorea javanica. I. Introduction. BIOTROPIA, 1(1), 42-45.

Table 20a. Damara: exports from Indonesia, and destinations, 1988-93
(tonnes)

 

1988 

1989 

1990 

1991 

1992 

1993 

Total 

1665 

1374 

952 

2198 

2376 

3031 

Of which to :

Singapore 

659 

994 

778 

1583 

1902 

2171 

Japan 

289 

136 

109 

136 

121 

123 

Germany 

118 

63 

30 

90 

75 

90 

China (Taiwan) 

15 

15 

15 

130 

100 

229 

Malaysia 

40 

25 

15 

98 

16 

76 

Pakistan 

531 

Netherlands 

13 

15 

UK 

78 

45 

France 

25 

13 

48 

93 

Korea, Rep. Of 

20 

75 

Viet Nam 

18 

Hong Kong 

10 

20 

15 

Sri Lanka 

18 

18 

India 

-

20 

234 

Colombia 

38 

Source: National statistics

Note: a : Classified as "Gum damar"
 
 

Table 20b. Damara (batu): exports from Indonesia, and destinations, 1988-93
(tonnes)

 

1988 

1989 

1990 

1991 

1992 

1993 

Total 

5749 

6549 

6571 

6206 

5214 

7440 

Of which to :

Singapore 

4563 

4890 

5021 

4581 

2962 

4242 

Germany 

700 

1408 

1105 

1250 

2092 

1966 

Malaysia 

385 

170 

264 

315

163 

India 

29 

28 

168 

60 

121 

818 

China (Taiwan) 

52 

15 

16 

15 

Pakistan 

14 

23 

13 

Bangladesh 

223 

Netherlands 

20 

Poland 

24 

Source: National statistics

Note: a : Classified as "Resin: Batu"
 
 
 

Table 20c. Damara (mata kucing): exports from Indonesia, and destinations, 1988-93
(tonnes)

 

1988 

1989 

1990 

1991 

1992 

1993 

Total 

2929 

3449 

3355 

4169 

2585 

2814

Of which to :

Singapore 

2714 

3122 

2710 

3072 

2265 

2114 

China (Taiwan) 

160 

207 

612 

821 

115 

304 

India 

41 

20 

20 

68 

219 

Germany 

31 

15 

76 

77 

Malaysia 

55 

33 

15 

Japan 

27 

Italy 

15 

10 

France 

13 

Korea, Rep. Of 

200 

Ecuador 

36 

UK 

16 

32 

Saudi Arabia 

12 

Syria 

24 

China,P.Rep.(excl.Taiwan) 

19 

Source: National statistics

Note: a : Classified as "Resin: Mata kucing"
 
 

Table 21. Damar: exports from Thailand, and destinations, 1988-93
(tonnes)

 

1988 

1989 

1990 

1991 

1992 

1993 

Total 

2107 

2328 

1499 

1841 

1391 

1475 

Of which to :

India 

2031 

2295

1499 

1841 

1372 

1475 

Singapore 

64 

17 

Pakistan 

10 

Tunisia 

16 

Bangladesh 

17 

Myanmar 

Source: National statistics
 
 


MASTIC

DESCRIPTION AND USES

Although usually termed a gum, mastic is a hard resin, produced by tapping the stem bark of the small tree Pistacia lentiscus, which is cultivated on the Greek islands of Chios.

Mastic is produced in the form of small tears, pale yellow in colour, clear and glassy in nature and liable to fracture. Its age-long use in Arab countries has been for chewing, where it sweetens the breath and helps preserve the teeth and gums. Its aromatic properties also make it suitable as a flavouring agent for alcoholic beverages. In the past it was also used in the manufacture of high-grade varnishes for paintings, and for medicinal purposes.

An essential oil can be distilled from the gum and finds some use for fragrance and flavouring purposes.

WORLD SUPPLY AND DEMAND TRENDS

Markets

Since Greece is by far the most important source of internationally traded mastic, production in Chios is also a fair measure of world demand. In the mid-1940s, annual production was around 300 tonnes. Greek sources estimated production at about 250 tonnes and 200 tonnes in 1961 and 1963, respectively. In 1975, production was put at 300 tonnes. Demand appears, therefore, to have been maintained at around 200-300 tonnes annually for some time. Recent figures are not known.

Apart from the Middle Eastern countries, where mastic is used for chewing, the United States and Europe also import it. In the United States and Europe, part of the mastic is distilled to produce essential oil.

Supply sources

Greece is by far the most important (and may well be the only) source of mastic of commerce. Production levels have been indicated above. Countries such as Algeria and Morocco have offered occasional, small quantities in the past.

Quality and prices

There are a number of different grades of mastic corresponding to degrees of cleanliness and size and shape of the tears. Exuded resin that has not been allowed to drop to the ground before collection and has formed perfect tears is the best quality and fetches the highest price.

An illustrative price for small quantities of No. 1 small tears (mid-1995, CIF London) is US$ 60/kg. Discounts are available for larger quantities. There has been a steady upward trend in prices in recent years.

PLANT SOURCES

Botanical name

Family Anacardiaceae: Pistacia lentiscus L. var. chia

Description and distribution

P. lentiscus is an evergreen, shrubby tree which normally grows to a height of about 2-4 m; exceptionally, it may grow to about 5 m. It is slow growing and long lived, and attains its full development at 50-60 years. The natural habit of the plant is bush-like, but under cultivation for mastic gum only one or two shoots are allowed to grow and develop into stems; the mature plant consists of one or two thick, contorted stems with an umbrella-shaped crown.

Other Pistacia species, such as P. vera, yield an exudate resin but P. lentiscus is the only one which is tapped commercially.

P. lentiscus prefers an arid, sub-tropical climate and occurs in coastal Mediterranean regions of both southern Europe and north Africa, and some of the islands in the Mediterranean such as Sicily, Sardinia and Cyprus. However, it is only cultivated for mastic on the Aegean island of Chios, where it occurs as P. lentiscus var. chia; it is often interspersed with olive trees.

COLLECTION/PRIMARY PROCESSING

In Chios, tapping and collection of the resin is limited to a 3-month period in late summer between July and October. The first light tappings are made when the tree is about six years old. A number of short, shallow incisions are made into the bark of the stem and the main branches. The wounds penetrate a few mm into the bark as far as the cambium; the number of wounds depends on the age and size of the tree. Further cuts are made at approximately one-week intervals. The first tapping period continues for 5-6 weeks and after a further 10 days, during which time the last of the exuded resin dries and solidifies, the first collection is made. This entails picking up pieces of resin that have fallen on the ground as well those adhering to the trunk of the tree. A second tapping and collection is made in the second half of the season.

After collection, the mastic is laid out to dry and foreign matter is removed by a combination of sieving and hand picking. The semi-cleaned resin is then soaked in water which serves to remove most of the adhering dirt and smaller impurities; it also gives the pieces of resin an added lustre.

Yields

The mastic plant starts yielding reasonable amounts of resin, about 30 g/year, at 10-12 years of age. Yields then gradually increase to about 300-400 g per tree at the age of 50-60 years. Individual trees have been known to yield up to 1 kg under favourable conditions.

VALUE-ADDED PROCESSING

An essential oil can be produced in 1-3% yield by steam distillation of the resin. Extraction of the resin with a suitable solvent yields a mastic resinoid.

PRODUCTS OTHER THAN RESIN

No other products of economic value are obtained from the tree.

DEVELOPMENTAL POTENTIAL

The market for mastic is firm but modest. If supplies continue to be available from Chios, then there is unlikely to be much scope for new entrants to the market, whether from wild or cultivated plant sources. Given also that P. lentiscus is slow growing, that the traditional mastic comes from a particular variety that occupies an ecological niche in Chios, and that it is some years before any economic returns are gained from cultivated plants, there is little developmental potential in mastic as far as new producers are concerned.

SELECTED BIBLIOGRAPHY

CHENOPOULOS, D. (1961) [Pistacia lentiscus and mastic production in Chios] (in Greek). Dasika Chronika, 3(4/5), 140-149.

DAVIDSON, D.F.D. (1948) Report on the gum mastic industry in Chios. Bulletin of the Imperial Institute, 46(2-4), 184-191.

GUENTHER, E. (1952) Oil of mastic. pp 169-170. In The Essential Oils, Vol. 5. New York: Van Nostrand Co.

KATSIOTIS, S, and OIKONOMOU, N.G. (1984) Qualitative and quantitative GLC analysis of the essential oil of Pistacia lentiscus (mastic) from different districts of Chios Island. Pharmkeutikon Deltion Epistemonike Ekdosis, 10(1), 17-28.

MARNER, F.J., FREYER, A. and LEX, J. (1991) Triterpenoids from gum mastic, the resin of Pistacia lentiscus. Phytochemistry, 30(11), 3709-3712.

PAPAGEORGIOU, V.P., MELLIDIS,A.S. and ARGYRIADOU, N. (1991) The chemical composition of the essential oil of mastic gum. Journal of Essential Oil Research, 3, 107-110.

PICCI, V., SCOTTI, A., MARIANI, M. and COLOMBO, E. (1987) Composition of the volatile oil of Pistacia lentiscus L. of Sardinian origin. pp 107-110. In Flavour Science and Technology. Martens, M., Dalen, G.A. and Russwurm, H. (eds.). New York: John Wiley & Sons.

SCRUBIS, B., MARKAKIS, P. and ZABIK, M.J. (1975) Essential oil of mastic gum. International Flavours and Food Additives, 6(6), 349 and 356.

TSITSA, S. (1963) The mastic shrub of Chios. Dasika Chronika, 5(8), 364-366.
 
 


DRAGON'S BLOOD

DESCRIPTION AND USES

The term "dragon's blood" has been applied since ancient times to the red coloured resin obtained from a large number of plant species of different geographic and botanical origin: from the Middle East, Southeast Asia and South America, and from amongst several different families of plants. The resin of commerce is in the form of powder, granules, sticks or friable lumps with a deep, dull red colour.

Traditionally, dragon's blood has been, and still is, used for medicinal purposes, whatever the source. In the past it has found minor use in coloured varnishes, lacquers and wood stains, although its use for this purpose (other than locally) is now largely confined to very specialized markets, such as violin varnish.

WORLD SUPPLY AND DEMAND TRENDS

Markets

It is extremely difficult to estimate the size of the market for internationally traded resin, but it is probably not more than a few hundred tonnes annually, and may be much less.

Domestic consumption in those countries where dragon's blood is popular as a traditional medicine is equally difficult to estimate, but demand in countries such as Peru and Ecuador, where Croton is the botanical source, is believed to be significant.

The main source of dragon's blood of commerce is Indonesia, and exports from Indonesia for the period 1988-93 are given in Table 22. Apart from Pakistan in 1991, all recorded exports went to Singapore and Hong Kong, so the final destinations - assuming most is re-exported - are not known.

Supply sources

Indonesian exports, probably originating in Sumatra, averaged just over 50 tonnes/year during 1988-93, with a peak of almost 90 tonnes in 1991. The scale of domestic consumption is not known so it is not possible to say by how much production might exceed the levels of exports.

Resin from plants growing in Yemen, the Canary Islands and sources in South America are not believed to enter world trade.

Quality and prices

Dragon's blood of Indonesian origin is available as sticks ("reed") or cakes ("lump"). In mid-1995, Indonesian dragon's blood was quoted by one London dealer at US$ 60/kg for small quantities (cf US$ 42/kg in 1992). Another dealer quoted US$ 33/kg for No. 1 grade and US$ 5/kg for No. 2 grade, both of Middle Eastern origin.

PLANT SOURCES


Botanical/common names

Family Palmaceae:

Daemonorops draco Blume East Indian dragon's blood
D. didymophylla
D. micranthus Becc.
D. motleyi Becc.

Family Agavaceae:

Dracaena cinnabari Balf. f. Socotra dragon's blood
D. draco Canary dragon's blood

Family Euphorbiaceae:

Croton draconoides (Muell.) Arg.
C. draco Schlect
C. lechleri L.
C. urucurana Baill.
C. xalapensis H.B.K.

Description and distribution

Daemonorops spp. are climbing jungle palms and the source of cane in Southeast Asia. In D. didymophylla, spiny stems bear bunches of scaly fruits which are covered in the red resin. In the past, the main areas of exploitation for resin have been the islands of Sumatra and Borneo, and some parts of Peninsular Malaysia.

Dracaena spp. are mostly trees of the Old World. D. cinnabari is endemic to the island of Socotra, Yemen. D. draco occurs on the Canary Islands.

Numerous Croton spp. which yield a blood red latex (Sangre de Drago) occur in Mexico, Central America and South America (e.g., Venezuela, Ecuador, Peru, Brazil).

COLLECTION/PRIMARY PROCESSING

Dragon's blood resin obtained from Daemonorops is present as a brittle layer on the surface of the immature fruit. After picking, the fruits are dried and placed in bags, which are then beaten to dislodge the resin. The resinous powder thus obtained is then sifted and warmed so that it can be moulded into sticks or formed into irregular shaped lumps.

Resin from Dracaena and Croton is obtained by making incisions into the stem of the plant and collecting the exudate.

Yields

No information is available on yields of resin from any of the botanical sources.

VALUE-ADDED PROCESSING

No further processing is carried out until the resin is ready for formulation by the consuming industry.

PRODUCTS OTHER THAN RESIN

Apart from local use as a source of cane in Southeast Asia, no other products of economic value are known to come from the species which yield dragon's blood.

DEVELOPMENTAL POTENTIAL

Unless some of the traditional medicinal uses of dragon's blood are developed into more widely used products, there appears to be very little developmental potential for the plants or the resins they produce.

SELECTED BIBLIOGRAPHY

HIMMELREICH, U., MASAOUD, M., ADAM, G. and RIPPERGER, H. (1995) Damalachawin, a triflavonoid of a new structural type from dragon's blood of Dracaena cinnabari. Phytochemistry, 39(4), 949-951.

MILBURN, M. (1984) Dragon's blood in East and West Africa, Arabia and the Canary Islands. Africa, 39(3), 486-493.

PIETERS, L., de BRUYNE, T., MEI, G., LEMIERE, G., VAN DEN BERGHE, D. and VLIETINCK, A.J. (1992) In vitro and in vivo biological activity of South American dragon's blood and its constituents. Planta Medica, 58(7), A582-583.

PIOZZI, F., PASSANNANTI, S. and PATERNOSTRO, M.P. (1974) Diterpenoid resin acids of Daemonorops draco. Phytochemistry, 13, 2231-2233.

RAO, G.S.R., GERHART, M.A., LEE, R.T., MITSCHER, L.A. and DRAKE, S. (1982) Antimicrobial agents from higher plants. Dragon's blood resin. Journal of Natural Products, 45(5), 646-648.
 
 

Table 22. Dragon's blood: exports from Indonesia, and destinations, 1988-93
(tonnes)

 

1988 

1989 

1990 

1991 

1992 

1993 

Total 

26 

59 

71 

87 

47 

25 

Of which to :

Singapore 

19 

56 

59 

36 

38 

23 

Hong Kong 

12 

20 

Pakistan 

31 

Source: National statistics