Gums, resins and latexes of plant origin

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:

• 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.

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:

• 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.

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:

• 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:
(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 resins^a (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	-	1	7
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	6
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 latexes^a: 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	3	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	-	2	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, 1987/88-1993/94^a
(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	6	3	30	30	1	80	83
Asian gum	23	41	6	37	12	6	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	1	18	87	45
Others	31	14	7	2	6	18	9

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 resins^a: 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	3	59	3
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.

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