INTRODUCTIONApart 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 LATEXESROBBINS (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:
- The intrinsic properties of the gum or resin, i.e., genetic factors which are determined mainly by the particular species from which the gum or resin is obtained, although there may also be provenance and individual tree differences in quality. Thus, all other things being equal, Acacia senegal furnishes a better quality "gum arabic" than any other Acacia species.
- Environmental factors. Climatic and edaphic factors have some effect on gum and resin quality, although the nature and size of the effects are not well documented.
- Harvesting, cleaning and handling practices. Apart from the species of plant which is exploited, and over which there may be no choice for the producer, these man-made effects have the greatest influence on quality.
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 REPORTMany 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:
- Description and uses. The physical form of the gum, resin or latex when it enters trade, and its physical and chemical properties; a brief note on its botanical and geographical origin; its uses including, where appropriate, the form in which it is used (for example, if an extract or distilled oil is prepared from it).
- World supply and demand trends. The export markets and producer countries as indicated by trade statistics and other sources of information; quality variation, grades and prices. (N.B. Although extensive use is made of trade statistics, they should always be interpreted with some caution; where recognized, instances of misclassification are noted in the report.)
- Plant sources. Botanical and common names of the main species concerned; their description and distribution (the description is not intended to be a detailed botanical one but simply one which indicates the approximate size and form of the plant and any characteristic features); an indication of whether wild or cultivated sources are exploited.
- Collection/primary processing. Methods of tapping and treatment prior to the gum, resin or latex entering trade, including cleaning; yields, including quantitative data, where available, and an indication of the factors which influence yields.
- Value-added processing. The type of value-added processing which is carried out in consuming countries and the opportunities for doing so in producer countries.
- Products other than gum, resin or latex. Any other products of economic value obtained from the plant (such as timber, fruits or feedstuffs).
- Developmental potential. The opportunities for new or improved production (having regard for the demand which exists), particularly under conditions of sustainable agroforestry when there is a threat to the wild resource using present methods of harvesting; research needs.
- Selected bibliography. A listing of what are judged to be the more important references so that those who wish to obtain more detailed information on the subject can do so. Where possible, and unless they are the only sources of information, old references have been avoided. (N.B. A bibliography of general articles and books on gums, resins and latexes is given as Appendix 1.)
- Statistical tables are appended at the end of each product discussed, following the selected bibliography.
- Olibanum (frankincense), myrrh and opopanax resins from Boswellia and Commiphora spp. (Flavours and Fragrances of Plant Origin. Non-Wood Forest Products 1. Rome: FAO, 1995).
- Pine resin and its primary products from Pinus spp. (Gum Naval Stores: Turpentine and Rosin from Pine Resin. Non-Wood Forest Products 2. Rome: FAO, 1995).
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:
(b) Guar gum from Cyamopsis tetragonoloba
Psyllium gum from Plantago spp.
Guayule latex from Parthenium argentatum
Rubber latex from Hevea brasiliensis
(c) Gellan 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:
Cashew from Anacardium occidentale
Ghatti from Anogeissus latifolia
Gum arabic-like gums from Combretum, Albizia and
Gum from Cassia spp. (e.g., C. tora)
Gum from Sesbania spp. (e.g., S. bispinosa)
Semla from Bauhinia retusa
Tamarind from Tamarindus indica
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.
Chilte from Cnidoscolus spp.
Many other gums, resins and latexes have been the subject of research reports but these are not discussed further here.
REFERENCESANDERSON, 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|
|Dipterocarp- aceae||SE Asia|
|Dragon's blood||Daemonorops||Palmaceae||SE Asia|
|Styrax||Liquidambar||Hamamelidaceae||Asia Minor, |
|Gutta percha||Palaquium||Sapotaceae||SE Asia|
Table 2. Gums and resinsa (excluding gum arabic): imports into the
European Community, and sources, 1988-93
|Of which from|
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)
|Of which :|
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
|Of which :|
|"Other natural gums"|
|"Other gum resins"|
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
Table 5. Gums and resinsa: exports from the People's Republic of China,
and destinations, 1990-92
|Of wich to:|
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.
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