Gum Arabic

 

Gum Arabic

Gum Arabic – There are two main types of gum arabic used as hydrocolloids: Acacia Senegal and Acacia Seyal. Senegal grade is an emulsifier, much used in beverage emulsions. Seyal grade is used in confectionery, coatings and as a soluble dietary fiber.

SYNONYMS Acacia gum, arabic gum;
INS No. 414
DEFINITION Gum Arabic is a dried exudate obtained from the stems and branches of Acacia senegal (L.) Willdenow or closely related species of Acacia (fam. Leguminosae). A. seyal is a closely related species. Gum arabic consists mainly of high-molecular weight polysaccharides and their calcium, magnesium, and potassium salts, which on hydrolysis yield arabinose, galactose, rhamnose, and glucuronic acid. Items of commerce may contain extraneous materials such as sand and pieces of bark which must be removed before use in food. Gum arabic from A. seyal is sometimes referred to as gum talha.
C.A.S. number 9000-01-5
DESCRIPTION Gum Arabic from A. senegal is a pale white to orange-brown solid, which breaks with a glassy fracture. The best grades are in the form of whole, spheroidal tears of varying size with a matte surface texture. When ground, the pieces are paler and have a glassy appearance. Gum from other acacia species may not have the characteristic tear shape and are often darker in colour. Gum from A. seyal is more brittle than the hard tears of A.senegal. Gum arabic is also available commercially in the form of white to yellowish-white flakes, granules, powder, roller-dried, or spray-dried material.
FUNCTIONAL USES Emulsifier, stabilizer, and thickener
CHARACTERISTICS
IDENTIFICATION
Solubility One gram dissolves in 2 ml of water forming a solution which flows readily and is acid to litmus, insoluble in ethanol
Hydrolysis products Passes test
See description under TESTS
Optical rotation Gum from A. senegal: water solutions are levorotatory
Gum from A. seyal: water solutions are dextrorotatory
See description under TESTS
PURITY
Loss on drying Not more than 15% (105°, 5h) for granular and not more than 10% (105°, 4h) for spray-dried material
Unground samples should be powdered to pass through a No. 40 sieve and mixed well before weighing
Total ash Not more than 4%
Acid insoluble ash Not more than 0.5%
Acid insoluble matter Not more than 1%
Arsenic Not more than 3 mg/kg (Method II)
Lead Not more than 5 mg/kg
Prepare a sample solution as directed for organic compounds in the Limit Test, using 5 m g of lead ion (Pb) in the control
Starch or dextrin Passes test
See description under TESTS
Tannin-bearing gums Passes test
See description under TESTS
Microbiological criteria Salmonella Spp. Negative per test
E. coli Negative in 1 g
TESTS
IDENTIFICATION TESTS
Hydrolysis products Identify arabinose, galactose, rhamnose and glucuronic acid as follows:

Boil a mixture of 100 mg of the sample and 20 ml of 10% sulfuric acid for 3h. Allow to cool and add excess barium carbonate, mixing with a magnetic stirrer until the solution is of pH 7, and filter. Evaporate the filtrate in a rotary evaporator at 30-50° in vacuum until a crystalline or syrupy residue is obtained. Dissolve in 10 ml of 40% methanol. This is the hydrolysate.

Place 1 to 10 m l spots of the hydrolysate on the starting line of two chromatoplates and spots containing 1 to 10 m g of arabinose, galactose, rhamnose and glucuronic acid, expected to be present in the hydrolysate. Use two solvent systems one for each plate: A. a mixture of formic acid, methyl ethyl ketone, tertiary butanol and water (15:30:40:15 by volume) and B. a mixture of isopropanol, pyridine, acetic acid and water (40:40:5:20 by volume) to develop the plates. After development, spray with a solution of 1.23 g anisidine and 1.66 g phthalic acid in 100 ml ethanol and heat the plates at 100° for 10 min. A greenish yellow colour is produced with hexoses, a red colour with pentoses and a brown colour with uronic acids. Compare sample spots with those for the solutions of arabinose, galactose, rhamnose and glucuronic acid. Additional spots corresponding to mannose, xylose, and galacturonic acid should be absent.

Optical rotation Test a solution of 10 g of sample (dry basis) in 100 ml of water (if necessary, previously filtered through a No. 42 paper or 0.8 m m millipore filter), using a 200-mm tube.
PURITY TESTS
Starch or dextrin Boil a 1 in 50 solution of the sample, cool and add a few drops of iodine TS. No bluish or reddish colour should be produced.
Tannin-bearing gums To 10 ml of a 1 in 50 solution of the sample add about 0.1 ml of ferric chloride TS. No blackish colouration or blackish precipitate should be formed.