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GUM ARABIC

Acacia senegal

Family
Mimosaceae (Leguminosae - Mimosoideae)

Vernacular names
Gum tree, gum arabic tree, three-thorned acacia (En). Gommier blanc, gommier (Fr). Aiti, kikwata, mgunga (Swahili).

Origin and geographic distribution
Acacia senegal grows in tropical and sub-tropical, arid and semi-arid regions and is very drought resistant. Trees survive in the most adverse conditions, subject to hot winds and sandstorms on the poorest soils of rock and sand. Acacia senegal is widely distributed in the drier parts of tropical Africa, from Senegal and Mauritania in the west to Eritrea and Ethiopia in the north-east and to South Africa in the south. Of the 4 recognized varieties var. senegal is the most widespread.

Gum arabic is sap from the branches of Acacia Senegal trees. It's a natural emulsifier, which means that it can keep together substances which normally would not mix well. Pharmaceutical companies use it to keep medicines from separating into their different ingredients, and a dab of gum arabic makes newspaper ink more cohesive and permanent.

According to Sudanese sources, gum arabic was an article of commerce as early as the 12th century BC. It was collected in Nubia and exported north to Egypt for use in the preparation of inks, watercolors and dyes. Herodotus, writing in the fifth century BC, mentions its use in embalming in Egypt. In the ninth century of our era, the Arab physician Abu Zayd Hunayn ibn Ishaq al-Ibadi, writing in his Ten Treatises on the Eye, described gum arabic as an ingredient in poultices or eye compresses.

In Africa today, individual farmers use gum arabic for other, more traditional uses, and heaps of gum arabic can be found in most local markets. It is said to soothe sore throats, soothe stomach and intestinal disorders, diarrhea, and constipation, treat eye problems and combat hemorrhages and the common cold.  It can be used as an emollient, astringent or cosmetic.  The flowers are a source of honey. The seed pods of Acacia senegal, 8 to 13 centimeters long (3–5") with flat seeds inside, make excellent fodder for livestock. Left unprotected, the trees will be browsed by sheep, goats, camels, impala and giraffe. Dried and preserved seeds are eaten by some people as a vegetable. The seed contains a fat which is used both in medicine and for soap making. Cordage is made from the roots, either directly or after beating to extract the fibres; its strength makes it suitable for well ropes and fishing nets. When the trees have passed their gum-bearing age, the wood is used both for fuel and in charcoal production. The dark heartwood is so hard that it makes excellent weavers’ shuttles. Gum arabic is still used locally in special dishes and as chewing gum; it has medicinal applications for both humans and livestock, e.g. to treat skin diseases and inflammation.

The food industry uses 60–75% of the world production. In confectionery, gum arabic is used to prevent crystallisation of sugar, as an emulsifier, and as a glaze or topping in bakery products; in soft drinks and alcoholic drinks it is used either as a vehicle for flavouring or as a stabiliser or clouding agent; in frozen dairy products gum arabic is used for encapsulating flavours such as citrus oils. Its pharmaceutical use has decreased, but it is still used as a suspending or emulsifying agent and in tablet manufacture, where it functions as a binding agent or as a coating prior to sugar coating.Gum arabic is also used in sweeteners and as an additive in foods and beverages, as a thickener in liquids, including soft drinks, and in food flavorings. It's a key ingredient in soft drinks. It is used to manufacture pharmaceutical capsules and to coat pills, and in the manufacture of vitamins, lotions and mascara and other cosmetics. Gum arabic is also a valuable addition to sweets, one supplier’s Web site adds, “including chocolates, jujubes, and cookies.” In human nutrition, gum arabic has less than 1 cal/g.

Today gum arabic is used as a natural "prebiotic," which stimulates the growth of healthy bacteria in the stomach.In Europe, gum arabic is admitted as food additive under No E414; in the United States it has FDA GRAS (generally recognized as safe) status.

Gum arabic is unique among the natural gums because of its extreme solubility in water and its lack of taste. As a food additive, it has been extensively tested and appears to be one of the safest for human consumption. In beverages, gum arabic helps citrus and other oil-based flavors remain evenly suspended in water. In confectionery, glazes and artificial whipped creams, gum arabic keeps flavor oils and fats uniformly distributed, retards crystallization of sugar, thickens chewing gums and jellies, and gives soft candies a desirable mouth feel. In cough drops and lozenges, gum arabic soothes irritated mucous membranes. Many dry-packaged products, such as instant drinks, dessert mixes and soup bases, use it to enhance the shelf life of flavors. In cosmetics, too, it smoothes creams, fixatives and lotions.

World trade in gum arabic reached about $90 million in 2000. Some 56 percent of the traded volume came from Sudan, and much of the remainder was exported from Chad and Nigeria. Sudan’s historically dominant position in the modern gum-arabic trade is a result of excellent soil conditions for Acacia senegal in much of the country and the long experience of many Sudanese in collecting and sorting the gum to yield the consistent quality grades that high-tech manufacturers rely on. One major us importer told me that “the tree can grow in Australia, New Mexico, Benin—but the gum isn’t right.”

Mussa Mohamed Karama, former general manager of the Gum Arabic Company of Sudan, points out that several million Sudanese—the country’s population is 29 million—are involved in some aspect of the gum-arabic trade. “The tree doesn’t need foreign components to produce,” says Karama. “You don’t have to fertilize it; you don’t have to water it or add chemicals. It grows naturally, and with minimum effort you collect the gum.” Anthony Nwachukwu, president of Atlantic Gums Corporation, a Connecticut importer of gum arabic, adds, “The employment opportunities at collection centers are really important for women. The gum harvesting season presents them with one of the few opportunities to earn real cash.”

Thus a drop of sap hardened in the hot African sun is plucked, sorted, bagged, shipped, ground into powder and added to a product you purchase, improving its qualities. Also “improved” are the farmer who owns the trees, the laborer who collected the gum and the women who sorted it—a chain of beneficiaries that has existed for at least two millennia, ever since Arab traders first introduced gum arabic to the western world.

The modern industrial era has produced an explosion of manufacturing uses for gum arabic. In the 19th century, it was important to early photography as an ingredient in gum bichromate prints. Today it is used in lithography, where its ability to emulsify highly uniform, thin liquid films makes it desirable as an antioxidant coating for photosensitive plates. The same quality also makes it useful in sprayed glazes and high-tech ceramics and as a flocculating agent in refining certain ores. It is a binder for color pigments in crayons, a coating for papers and a key ingredient in the micro-encapsulating process that produces carbonless copy paper, scratch-and-sniff perfume advertisements, laundry detergents, baking mixes and aspirins. It is used in textile sizing and finishing, metal corrosion inhibition and glues and pesticides. Moisture-sensitive postage-stamp adhesives rely on it.

Properties
Gum arabic is a pale to orange-brown solid, which breaks with a glassy fracture. The best grades have the shape of whole, round tears, orange-brown in colour and with a matt surface texture; after processing to the broken or ‘kibbled’ state the pieces are much paler and have a glassy appearance. Unlike many other vegetable gums, gum arabic dissolves very well in water (up to 50%). The solution is colourless and free of taste and does not readily interact with other chemical compounds. Chemically, gum arabic is a slightly acidic complex composite of glycoproteins and polysaccharides and their calcium, magnesium and potassium salts.