Title: Acacia
CAS Registry Number: 9000-01-5
Additional Names: Gum Arabic
Literature References: Estimations of mol wt range from about 240,000: Oakley, Trans. Faraday Soc. 31, 136 (1935), to 580,000: Anderson et al., Carbohydr. Res. 3, 308 (1967). According to the U.S.P., acacia is the dried gummy exudation from the stems and branches of Acacia senegal (L.) Willd., Leguminosae, or other African species of Acacia. According to C. L. Mantell, The Water-Soluble Gums (New York, 1947), Kordofan gum (hashab geneina), the gum from Acacia verek Guill. & Perr. from plantations in the Kordofan province (Sudan) is considered the best commercial variety. Grades of Kordofan gum which are clear, white (sun bleached) and tasteless are preferred for food prepns and pharmaceuticals. (There is a close relationship between color and flavor due to the presence of tannins.) Acacia was originally thought to be composed only of (-)-arabinose, (+)-galactose, (-)-rhamnose, (+)-glycuronic acid. Revised composition and structural studies: Anderson et al., J. Chem. Soc. C 1966, 1959. See also Swenson et al., J. Polym. Sci. Part A-2 6, 1593 (1968). General review: Anderson, Dea, J. Soc. Cosmet. Chem. 22, 61-76 (1971). Review of use as food additive: D. M. W. Anderson, Food Addit. Contam. 3, 225-230 (1986).
Properties: Occurs in spheroidal tears up to 32 mm in diameter. Also flakes and powder. Solns of gum from Acacia verek are levorotatory; other acacia species are dextrorotatory: Hamy, Bull. Sci. Pharmacol. 35, 421 (1928). Specific gravity: 1.35-1.49 (samples dried at 100° are heavier). Moisture content usually varies from 13-15%. U.S.P. limit 15%. Material containing less than 12% chips easily and produces dust during transportation. Insol in alcohol. Almost completely sol in twice its weight of water. 100 grams of a satd soln contains 37 g at 25°; 38 g at 50°; 40 g at 90°: Taft, Malm, Trans. Kans. Acad. Sci. 32, 49 (1929). Aq soln acid to litmus. Also sol in glycerol and in propylene glycol, but prolonged heating (several days) may be necessary for complete solution (about 5%). Incompat. Precipitates or jellies result upon addition of solns of ferric salts, borax, basic lead acetate (lead subacetate, but not neutral lead acetate), alcohol, sodium silicate, gelatin, ammoniated tincture of guaiac.
Use: As mucilage, excipient for tablets, size, emulsifier, thickener, also in candy, other foods; as colloidal stabilizer. In the manufacture of spray-dried "fixed" flavors¾stable, powdered flavors used in packaged dry-mix products (puddings, desserts, cake mixes) where flavor stability and long shelf life are important. |