Mesquite (FAO, NWFP 6)
- Extract from : NWFP 6. Coppen J.J.W., 1995. Gums, resins and latexes of plant origin. FAO, Rome. 142 p. (Non-Wood Forest Products, 6). on line
DESCRIPTION AND USES
The term "mesquite gum" is used here to denote the ground endosperm of the seed from Prosopis spp., in particular Prosopis 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 Prosopis 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.
Family Leguminosae (Mimosoideae): Prosopis spp., especially Prosopis 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. Prosopis 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.
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 endospeiin 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 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 oneyear 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.
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.
The most pressing practical problem to be overcome is that of separating the seed from the pod and obtaining reasonably pure endospeim 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:
- Techno-economic evaluation of methods for obtaining seed endosperm of a satisfactory quality from mesquite.
- Investigation of the functional properties of mesquite gum vis-a-vis other seed gums.
- An investigation of the potential market for mesquite gum (domestic and international) and the economics of production (assuming the other aspects, above, have favourable outcomes).
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- 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, FR., 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.
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- FIGUEIREDO, A.A. (1987) [Industrialization of the pods of algaroba (Prosopis juliflora) aimed at the production of seed gum] (in Portuguese). Revista Associação 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.