Gum arabic

Gum arabic, a natural gum also called gum acacia, and chaar gund or char goond (in India), is a substance that is taken from two sub-Saharan species of the acacia tree, Acacia senegal and Acacia seyal. It is used primarily in the food industry as a stabilizer, but has had more varied uses in the past, including viscosity control in inks. Its E number is E414.

Gum arabic is a complex mixture of saccharides and glycoproteins, which gives it its most useful property: it is perfectly edible. Other substances have replaced it in situations where toxicity is not an issue, as the proportions of the various chemicals in gum arabic vary widely and make it unpredictable. Still, it remains an important ingredient in soft drink syrups, "hard" gummy candies like gumdrops, marshmallows, M & M's chocolate candies, and most notably, chewing gums. For artists it is the traditional binder used in watercolor paint, and is used in photography for gum printing. Pharmaceuticals and cosmetics also use the gum, and it is used as a binder in pyrotechnic compositions. It is an important ingredient in shoe polish. It is also used often as a lickable adhesive on postage stamps and cigarette papers. Printers employ it to stop oxidation of aluminium printing plates in the interval between processing of the plate and its use on a printing press.

The substance is grown commercially throughout the Sahel from Senegal and Sudan to Somalia.

Painting and Art
Gum arabic is used as a binder for watercolor painting because it dissolves easily in water. Pigment of any color is suspended within the gum arabic in varying amounts, resulting in watercolor paint. Water acts as a vehicle or a diluent to thin the watercolor paint and helps to transfer the paint to a surface such as paper. When all moisture evaporates, the gum arabic binds the pigment to the paper surface.

Photography
The historical photography process of gum bichromate photography uses gum arabic to permanently bind pigments on paper. Ammonium or potassium dichromate is mixed with gum arabic and pigment to create a photographic emulsion, sensitive to ultraviolet light.

Printmaking
Gum arabic is also used to protect and etch an image in lithographic processes. Ink tends to fill into whitespace on photosensitive aluminium plates if they don't receive a layer of gum. In lithography the gum etch is used to etch the most subtle gray tones. Phosphoric acid is added in varying concentrations to the gum arabic to etch the darker tones up to dark blacks. Multiple layers of gum are used after the etching process to build up a protective barrier that ensures the ink does not fill into the whitespace of the image being printed.

Political aspects
Although from the 1950s to the early 1990s Sudan accounted for roughly 80% of gum arabic production, today that figure is under 50%. However it is still the world's largest single producer, and the production of gum arabic is heavily controlled by the Sudanese government.

The connection between Sudan and Osama bin Laden brought the otherwise innocuous gum to public consciousness in 2001, as an urban legend arose that bin Laden owned a significant fraction of the gum arabic production in Sudan and that therefore one should boycott products using it. As a result, some food producers, such as Snapple, renamed the ingredient to "gum acacia" on their labels.

This story took on somewhat significant proportions, mostly thanks to an article in The Daily Telegraph a few days after the September 11 attacks, which echoed this claim. Eventually, the State Department issued a release stating that while Osama bin Laden had once had considerable holdings in Sudanese gum arabic production, he divested himself of these when he was expelled from Sudan in 1996.

In a press conference held at the Washington Press Club on 30 May, 2007, John Ukec Lueth Ukec, Sudan's ambassador to the United States, threatened to stop exportation of gum arabic from his country if sanctions were imposed. The sanctions proposed by the United States were a political response from the United States to the alleged connection between the government of Sudan and the Janjaweed militia group. Ukec made his speech surrounded by Coca-Cola products, although other sodas use gum arabic as an emulsifier as well.

John Ukec Lueth Ukec was quoted at the Washington press conference, "I want you to know that the gum arabic which runs all the soft drinks all over the world, including the United States, mainly 80 percent is imported from my country," which he said after raising a bottle of Coca-Cola. According to the Washington Post, a reporter then asked if Sudan was threatening to "stop the export of gum arabic and bring down the Western world." To which Ukec replied, "I can stop that gum arabic and all of us will have lost this," and gestured to the Coke bottle.

Pyrotechnics
Gum arabic is also used as a water soluble binder in firework composition.

Effect on surface tension in liquids
Gum arabic reduces the surface tension of liquids, which leads to increased fizzing in carbonated beverages. This can be exploited in what is known as a Diet Coke and Mentos eruption.