Gum arabic
Gum arabic (also gum arabic , arabic gum ) is the gum from the exudate of various acacia trees common in Africa and species that were formerly part of acacia , such as the gum arabic tree ( Senegalia senegal ) and the gum arabic acacia ( Vachellia nilotica ), the Seyal - Acacia ( Vachellia seyal ) and referred to by Vachellia tortilis , Vachellia gummifera , Vachellia karroo and the terrible acacia ( Vachellia horrida ).
Many other (non- official ) gums are also used by Vachellia spp., All of which were previously also considered to be Acacia species . , Acacia spp. and Senegalia spp. labeled with "gum arabic". It is the oldest known type of rubber.
Gum arabic is a natural mixture of polysaccharides (multiple sugars), the main component of which is also called arabinic acid .
Extraction
Gum arabic is extracted from the sap of the trees. You cut the peeled tree bark at a downward angle. Over the course of 20 to 30 days, the seeping rubber can form a superficially hard blister or worm-shaped, horn-shaped pieces, which are then “harvested”. The tree takes up to four years to recover from it. However, the tree itself also exudes rubber when the bark tears open due to drying out. The rubber is then dried further and usually subjected to further steps.
characterization
Gum arabic consists of white to red, mostly yellowish-brown, dull, brittle, odorless pieces with shiny , glassy breakage that dissolve in warm water to a clear, tough, sticky, bland-tasting liquid with a slightly acidic reaction ( pH value of 5 in 10% solution). It has a density of 1.4 g · cm -3 , and a decomposition temperature of 90 to 95 ° C . The solubility in water is around 500 g · l −1 . It is insoluble in alcohol .
Gum arabic mainly contains acidic alkaline earth and alkali salts of arabinic acid (polyarabic acid), a branched polysaccharide consisting of L - arabinose , D - galactose , L - rhamnose and D - glucuronic acid in a ratio of 3: 3: 1: 1. In the past, arabinose and ribose were obtained from this. It also contains glycoproteins .
Gum arabic is traded in large quantities and divided into three classes. Class 1 (the best; Senegalia senegal ) consists of large, round or worm-shaped pieces and is whitish / pale or brownish-yellow and hard. Class 2 ( Senegalia senegal and Vachellia seyal as well as other Acacia , Vachellia ) consists of rounded, worm-shaped or branched pieces and is rather crumbly. It's smaller and generally darker than the top quality. The poorest quality rubber (class 3; other types mixed in) is in the form of small brown grains.
It is also available in the form of flakes, granules and powders, or spray-dried .
Classification and labeling
| safety instructions | |||||||
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| Surname |
Gum arabic |
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| CAS number |
9000-01-5 |
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| EC number |
232-519-5 |
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| Toxicological data |
(not relevant for classification)> 16,000 mg kg −1 ( LD 50 , rat , oral ) |
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Gum arabic ( CAS number : 9000-01-5) is a hazardous material of to GHS with eyes Irritant - Category 2 and assigned corresponding to the pictogram GHS07 and the H-set H319: Causes severe eye irritation must be provided.
In the EU , gum arabic is approved as a food additive with the number E 414 .
Uses
medicine
Gum arabic has a strong astringent effect . It contains tannins, mucus and flavonoids. In ancient Egypt , gum arabic ( called kami there) was used to embalm the dead. It was also used to treat viral skin diseases. In the pharmacopoeia gum arabic is used as a medicinal drug , and as galenic listed excipient. It is z. B. used for local pain treatment and as a filler and thickener also in dentistry.
Food additive
As a food additive , gum arabic is added to foods as a thickener , emulsifier and stabilizer . The application in beverage emulsions as well as in the confectionery sector and in the manufacture of medicines (rubber articles and coating of dragees ) should be emphasized here. For example, in Coca-Cola without gum arabic, the black dye would settle on the bottle wall.
Gumming
A once widespread use of gum arabic is the rubber coating of paper . This means that labels , stamps , envelopes , cigarette paper , packaging or adhesive tapes can be closed or “glued” when they are moistened.
The saddler uses the gum arabic dissolved in water as a polishing agent for cut edges on sewn leather. The solution is applied with a felt and, after drying, polished with a soft cloth or a buffing disc . It closes the pores and gives the leather a darker patina and shine.
Gum arabic was also used in classic lithography for the necessary pretreatment of the litho stones before the actual paint application.
Pigment binder
Gum arabic is used to make artist's paints: for watercolor , gouache and tempera paints . It serves as a binding agent for the color pigments . In glass painting , too , the powdery, ceramic glass enamel paints are rubbed on so that they can be painted. In organ building , gum arabic is used in a mixture with chalk and a dye for surface protection and as a heat protection paint when soldering during the manufacture of metal pipes (mostly tin-lead alloy).
Louis-Alphonse Poitevin developed a photographic pigment process with gum arabic and chromates in 1855 . The rubber printing is one of the classic Alternative Process , which in 1858 by John Pouncy has been improved (1820 to 1894). It is still used today by artists and photographers.
A solution of gum arabic is called gum water . Ink was already made from rubber water and soot in ancient times in Egypt and China .
requirement
The annual world demand of 50,000 to 60,000 tons is covered to 50% from Sudan . It used to provide 85–90% of the demand. In the meantime, Chad , Senegal and Nigeria are also strong producers. When the US imposed a strict trade embargo on Sudan in 1997 , shortly afterwards they exempted gum arabic to ensure supplies of Coca-Cola.
literature
- Louis Edgar Andés: Gum arabic and its surrogates in solid and liquid state. Presentation of the types and properties of Arabic gum, its adulterations, manufacture of dextrin and other starch products, as well as the surrogates for gum made from dextrin and other materials. A. Hartleben's Verlag , Vienna 1896, OCLC 16389877 .
- Abdalbasit Adam Mariod: Gum Arabic: Structure, Properties, Application and Economics. Academic Press, 2018, ISBN 978-0-12-812002-6 .
- Berkshire Encyclopedia of World History. 2nd Edition, 2010, ISBN 978-1-933782-65-2 , pp. 1181 f.
- CW Fagg, GE Allison: Acacia senegal and the gum arabic trade: monograph and annotated bibliography. Tropical Forestry Papers No. 42, University of Oxford, 2004, ISBN 0-85074-157-2 , online , (PDF; 68.8 MB).
Web links
- Charles O. Cecil: Gum Arabic. at Saudi Aramco World, March / April 2005.
- Gum arabic . In: Merck's Warenlexikon . 3rd ed. 1884 ff., P. 179 f.
- Gum arabic from materialarchiv.ch, accessed on January 8, 2017.
Individual evidence
- ^ PH List, L. Hörhammer: Hager's handbook of pharmaceutical practice. Volume 4: Chemicals and Drugs CI – G. Springer, 1973, ISBN 978-3-642-80621-6 , pp. 1211-1217.
- ↑ Rudolf Hänsel, Konstantin Keller, Horst Rimpler, Gerhard Schneider (eds.): Hager's handbook of pharmaceutical practice. Drugs: A – D. 5th edition, Springer, 1992, ISBN 978-3-642-63468-0 , pp. 37-42.
- ^ A b Gerhard Eisenbrand, Peter Schreier: RÖMPP Lexikon Lebensmittelchemie. 2nd edition, Thieme, 2006, ISBN 978-3-13-736602-7 .
- ↑ a b Gerhard Franz: Structure and biological function of polysaccharides. In: Klaus Balser, Walther Burchard (Ed.): Polysaccharide. Springer Berlin Heidelberg, 1985, ISBN 978-3-540-13931-7 , pp. 1-14.
- ↑ Rebecca Ciesielski: Gum Arabic: Dependent on the crisis glue. In: Handelsblatt . March 14, 2015.
- ↑ Robert Ebermann, Ibrahim Elmadfa: Textbook food chemistry and nutrition. 2nd edition, Springer, 2011, ISBN 978-3-7091-0210-7 , pp. 659 ff.
- ↑ a b c d e Entry on gum arabic in the GESTIS substance database of the IFA , accessed on December 27, 2015(JavaScript required) .
- ↑ GUMMI ARABICUM data sheet , spray-dried (PDF) from Carl Roth , accessed on February 9, 2017.
- ↑ Eva Shenia Shemyakova: 'Des Juden buch von kreuczenach'. Investigation and edition of the recipe part of the Heidelberg Cpg 786. In: Fachproseforschung - Grenzüberreitungen. Volume 8/9, 2012/13, pp. 207–265, here: p. 225.
- ^ Abu Bakr Muḥammad ibn Zakariya Razi, William Alexander Greenhill: A Treatise on the Small-pox and Measles. Sydenham Society, 1848, OCLC 7083032 .
- ↑ Patent US2007299098 : Therapeutic Agent for Neuropathic Pain. Filed November 2, 2005 , published December 27, 2007 , inventor: Tsutomu Tanabe.
- ↑ a b Guillaume Pitron: Gum arabic, unknown and indispensable ( memento from January 1, 2015 in the Internet Archive ), In: Le Monde diplomatique . April 8, 2011.