Gum Arabic is the hardened sap of the acacia Senegal tree, which is found in the African grassland savannahs along the southern edge of the Sahara, and as far east as Oman and India.. It was given its name by the Europeans who were introduced to it in their early contact with the Arabs.
The acacia tree thrives on dry rocky hills and low-lying dry savannas and is extremely drought resistant and can survive sandstorms and temperatures up to 45 C (113F). During the first two years, saplings require protection from weeds and livestock but need little care after that. The trees reach six meters in height when mature. Their lateral root system makes them soil stabilizers, useful for erosion control. Their leaves are mineral rich and rehabilitate degraded soil when they drop and decompose.
The resin seeps from the trunk and principal branches, but the flow is usually hurried along by the harvester, who makes a long thin incision in the bark of the tree. In about fifteen days the sap thickens and hardens on exposure to the air, forming small round or oval masses. The coloring varies from white to red depending on the whether the tree is a red or white gum tree.
In Sudan, trees are farmed over very large areas of, propagated from seeds which are produced once every few years, or from shoot cuttings. Seedlings are exported from Sudan to other African countries like Niger. In many African countries acacia Senegal is part of a large scale sustainable agriculture, forest management and rural-development strategies. The seed pods are used as fodder for livestock. Dried and preserved seeds are eaten by some people as a vegetable. 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. Ropes can be made from root bark fibers.
In Africa today gum Arabic can be found in local markets. It is to soothe sore throats, assuage stomach and intestinal disorders, treat eye problems and combat hemorrhages and the common cold. It can be used as an emollient, astringent or cosmetic.
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.
By the Middle Ages, gum Arabic was used in Europe by manuscript illustrators. They discovered that it can be applied very thinly on illuminated manuscripts with brilliant results in color and transparency. In Turkey, illuminators used gum Arabic to apply gold to manuscripts. They mixed 24-carat gold leaf with melted gum Arabic to make a gold paste, applied with fine brushes dipped in a gelatin solution.
In the 19th century, it was important to early photography as an ingredient in gum bichromate prints. 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, postage-stamp adhesives, in sweeteners and as an additive in foods and beverages, as a thickener in liquids, including soft drinks, and in food flavorings. It is used to manufacture pharmaceutical capsules and to coat pills.
Gum Arabic has the unusual characteristic that it can be almost completely dissolved in its own volume of water.
References: Saudi Aramco World, September/October 2006; http://www.botanical.com/botanical/mgmh/a/acaci006.html, http://www.hort.purdue.edu/newcrop/duke_energy/Acacia_senegal.html#Distribution