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.

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

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.

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.

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:
 

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.

MICROBIOLOGICAL ANALYSIS