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Gum arabic (gum acacia,gum sudani,Senegal gum and by other names[a]) is atree gum exuded by two species ofAcacia sensu lato:Senegalia senegal,[2] andVachellia seyal. However, the term "gum arabic" does not indicate a particular botanical source.[1] The gum is harvested commercially from wild trees, mostly inSudan (about 70% of the global supply) and throughout theSahel, fromSenegal toSomalia. The name "gum Arabic" (al-samgh al-'arabi) was used in the Middle East at least as early as the 9th century. Gum arabic first found its way to Europe via Arabic ports and retained its name of origin.[3]
Gum arabic is a complexmixture ofglycoproteins andpolysaccharides, predominantly polymers ofarabinose andgalactose. It issoluble in water, edible, and used primarily in thefood industry and soft drink industry as astabilizer, withE number E414 (I414 in the US). Gum arabic is a key ingredient in traditionallithography and is used inprinting,paints,glues,cosmetics, and various industrial applications, includingviscosity control ininks and intextile industries.
Gum arabic was defined by the 31st Codex Committee for Food Additives, held atThe Hague from 19 to 23 March 1999, as the dried exudate from the trunks and branches ofAcacia senegal orVachellia (Acacia) seyal in the familyFabaceae (Leguminosae).[4]: 4 A 2017 safety re-evaluation by the Panel on Food Additives and Nutrient Sources of theEuropean Food Safety Authority (EFSA) said that although the above definition holds true for most internationally traded samples, the term "gum arabic" does not indicate a particular botanical source; in a few cases, so‐called "gum arabic" may not even have been collected fromAcacia (in the broad sense) species, instead coming from e.g.Combretum orAlbizia.[1]
Gum arabic is a rich source ofdietary fibers, and, in addition to its widespread use in food and pharmaceutical industries as a safethickener,emulsifier, andstabilizer, it also possesses a broad range of health benefits that have been proven throughin vitro andin vivo studies.[5] Gum arabic is not degraded in the stomach, butfermented in the large intestine into a number of short chainfatty acids. It is regarded as aprebiotic that enhances the growth and proliferation of beneficial intestinalmicrobiota; therefore its intake is associated with many healthful effects.[6] These health benefits include:[5][7][8][9][10][11]
Gum arabic'smixture ofpolysaccharides andglycoproteins gives it the properties of aglue andbinder that isedible by humans. Other substances have replaced it wheretoxicity is not an issue, as the proportions of chemicals in gum arabic vary widely and make it unpredictable. It remains an important ingredient insoft drinksyrup and "hard" gummy candies such asgumdrops,marshmallows, andM&M's chocolate candies. Forartists, it is the traditionalbinder inwatercolorpaint and in photography forgum printing, and it is used as a binder inpyrotechnic compositions.Pharmaceutical drugs andcosmetics also use the gum as abinder,emulsifier, andsuspending agent orviscosity-increasing agent.[12] Wine makers have used gum arabic as awinefining agent.[13]
It is an important ingredient inshoe polish, and can be used in making homemadeincense cones. It is also used as a lickableadhesive, for example onpostage stamps,envelopes, andcigarette papers. Lithographic printers employ it to keep the non-image areas of the plate receptive to water.[14] This treatment also helps to stopoxidation ofaluminiumprinting plates in the interval between processing of the plate and its use on aprinting press.
Gum arabic is used in the food industry as astabiliser,emulsifying agent, andthickening agent inicing, fillings, soft candy,chewing gum, and otherconfectionery,[15] and to bind thesweeteners andflavorings insoft drinks.[16] A solution of sugar and gum arabic in water,gomme syrup, is sometimes used in cocktails to prevent the sugar from crystallising and provide a smooth texture.
Gum arabic is a complexpolysaccharide andsolubledietary fibre that isgenerally recognized as safe for human consumption.[17][18] An indication of harmlessflatulence occurs in some people taking large doses of30 g (1 oz) or more per day.[1] It is not degraded in theintestine, butfermented in the colon under the influence of microorganisms; it is aprebiotic (as distinct from aprobiotic). No regulatory orscientific consensus has been reached about itscaloric value; an upper limit of 2 kcal/g (8.4 kJ/g) was set for rats, but this is invalid for humans. The USFDA initially set a value of 4 kcal/g (17 kJ/g) for food labelling, but in Europe no value was assigned for solubledietary fibre. A 1998 review concluded that "based on present scientific knowledge, only an arbitrary value can be used for regulatory purposes".[19] In 2008, theFDA sent a letter of no objection in response to an application to reduce the rated caloric value of gum arabic to 1.7 kcal/g (7.1 kJ/g).[20]
Gum arabic is used as a binder forwatercolor painting because it dissolves easily in water.Pigment of any color is suspended within the acacia gum in varying amounts, resulting in watercolor paint. Water acts as a vehicle or adiluent to thin the watercolor paint and helps to transfer the paint to a surface such aspaper. When all moisture evaporates, the acacia gum typically does not bind the pigment to the paper surface, but is totally absorbed by deeper layers.[21]
If little water is used, after evaporation, the acacia gum functions as a true binder in a paint film, increasing luminosity and helping prevent the colors from lightening. Gum arabic allows more subtle control over washes, because it facilitates the dispersion of the pigment particles. In addition, acacia gum slows evaporation of water, giving slightly longer working time.[citation needed]
The addition of a little gum arabic to watercolor pigment and water allows for easier lifting of pigment from paper, thus can be a useful tool when lifting out color when painting in watercolor.[21]
Gum arabic has a long history as additives toceramic glazes. It acts as a binder, helping the glaze adhere to the clay before it is fired, thereby minimising damage by handling during the manufacture of the piece. As a secondary effect, it also acts as adeflocculant, increasing the fluidity of the glaze mixture, but also making it more likely to sediment out into a hard cake if not used for a while.[citation needed]
The gum is normally made up into a solution in hot water (typically 10–25 g/L; ¼ to ½ oz per pint), and then added to the glaze solution after any ball milling in concentrations from 0.02% to 3.0% of gum arabic to the dry weight of the glaze.[22] On firing, the gum burns out at a low temperature, leaving no residues in the glaze. More recently, particularly in commercial manufacturing, gum arabic is often replaced by more refined and consistent alternatives, such ascarboxymethyl cellulose.
The historicalphotography process ofgum bichromate photography uses gum arabic mixed withammonium orpotassium dichromate andpigment to create a coloured photographicemulsion that becomes relatively insoluble in water upon exposure toultraviolet light. Unreacted gum remains soluble and can be washed off in warm water so that the reacted gum arabic permanently binds the pigments onto the paper in the final print.[23]
Gum arabic is also used to protect andetch an image inlithographic processes, both from traditional stones and aluminum plates. In lithography, gum by itself may be used to etch very light tones, such as those made with a number-five crayon.Phosphoric, nitric, or tannic acid is added in varying concentrations to the acacia gum to etch the darker tones up to darkblacks. The etching process creates a gum adsorb layer within the matrix that attracts water, ensuring that the oil-based ink does not stick to those areas. Gum is also essential to what is sometimes called paper lithography, printing from an image created by a laser printer or photocopier.[citation needed]
Gum arabic is also used as a water-soluble binder infireworks composition.[24]
Arabinogalactan is a biopolymer consisting of arabinose and galactose monosaccharides. It is a major component of many plant gums, including gum arabic.8-5' Noncyclic diferulic acid has been identified as covalently linked to carbohydrate moieties of the arabinogalactan-protein fraction.[25]
While gum arabic has been harvested inArabia andWest Asia since antiquity, sub-Saharan acacia gum has a long history as a prized export. The gum exported came from the band of acacia trees that once covered much of the Sahel region, the southern littoral of theSahara Desert that runs from theAtlantic Ocean to theRed Sea. Today, the main populations of gum-producingAcacia species are found inMauritania,Senegal,Mali,Burkina Faso,Niger,Nigeria,Chad,Cameroon,Sudan,Eritrea,Somalia,Ethiopia,Kenya, andTanzania.[citation needed]Acacia is tapped for gum by stripping bits off the bark, from which gum then exudes. Traditionally harvested by seminomadic desert pastoralists in the course of theirtranshumance cycle, acacia gum remains a main export of several African nations, including Mauritania, Niger, Chad, and Sudan. Total world gum arabic exports were estimated in 2019 at 160,000 tonnes, having recovered from 1987 to 1989 and2003–2005 crises caused by the destruction of trees by thedesert locust.[citation needed]
In 1445, PrinceHenry the Navigator set up a trading post onArguin Island (off the coast of modern Mauritania), which acquired acacia gum andslaves for Portugal. With the merger of the Portuguese and Spanish crowns in 1580, the Spaniards became the dominant influence along the coast. In 1638, however, they were replaced by the Dutch, who were the first to begin exploiting the acacia gum trade. Produced by the acacia trees ofTrarza andBrakna, this acacia gum was considered superior to that previously obtained inArabia. By 1678, the French had driven out the Dutch and established a permanent settlement at Saint Louis at the mouth of the Senegal River.[26] Gum Arabic came to play an essential role in textile printing and therefore in pre-industrial economies of France, Great Britain and other European countries. Throughout the 18th century, their competition over the commodity was so fierce, that some have referred to it as the gum wars.[27]
For much of the 18th and 19th centuries, gum arabic was the major export from French and British trading colonies in modern Senegal and Mauritania. West Africa had become the sole supplier of world acacia gum by the 18th century, and its export at the French colony ofSaint-Louis doubled in the decade of 1830 alone. A threat to bypass Saint-Louis and taxes by sending gum to the British traders atPortendick, eventually brought theEmirate of Trarza into direct conflict with the French. In the 1820s, the French launched theFranco-Trarzan War of 1825.[citation needed] The new emir,Muhammad al Habib, had signed an agreement with theWaalo Kingdom, directly to the south of the river. In return for an end to raids in Waalo territory, the emir took the heiress of Waalo as a bride. The prospect that Trarza might inherit control of both banks of the Senegal struck at the security of French traders, and the French responded by sending a large expeditionary force that crushed Muhammad's army. The war incited the French to expand to the north of the Senegal River for the first time, heralding French direct involvement in the interior of West Africa.[28] Africa continued to export gum arabic in large quantities—from the Sahel areas ofFrench West Africa (modern Senegal, Mauritania, Mali, Burkina Faso, and Niger) andFrench Equatorial Africa (modern Chad) as well asBritish-administered Sudan, until these nations gained theirindependence in 1959–61.
Since the 1950s, the global supply of gum arabic has been dominated by Sudan.[29] In the early 2020s, about 70% of the global supply has been sourced from Sudan,[30] with approximately 5 million Sudanese people (more than 10 percent of a country's population) being directly or indirectly dependent on gum arabic for their livelihoods.[31] After market reforms in 2019, official figures showed that Sudan's exports of gum arabic were at about 60,000 tonnes in 2022, but exact numbers are difficult to ascertain because some production is in regions that are hard to access.[29][32] Before the reforms, the production of gum arabic was heavily dominated by the Sudanese government and in some periods there were attempts of using its importance to the global market as a leverage against other countries.[29][33] Since the2023 Sudan conflict, the export of gum arabic has been interrupted, causing a crash in its price in Sudan because of a reduced ability to export the product, whereas international companies that rely on it are attempting to diversify the supply chain of gum arabic and find alternative ingredients that can be used as a replacement.[29][34]
Gum arabic slows the rate of absorption of some drugs, includingamoxicillin, from the gut.[35]
In the works of English playwrightWilliam Shakespeare, Dutch poetJacob Cats and other European poets of the 13th to 17th centuries, gum arabic represented the "noble Orient". In the Sahel, it is a symbol of the purity of youth.[27]
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