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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.

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