Sodium alginate – JECFA specification

 Prepared at the 49th JECFA (1997) , published in FNP 52 Add 5 (1997) superseding specifications prepared at the 44th JECFA (1995), published in FNP 52 Add 3 (1995). An ADI ‘not specified’ was established at the 39th JECFA (1992)
DEFINITIONSodium salt of alginic acid
C.A.S. number9005-38-3
Chemical formula(C6 H7 NaO6)n
Structural formulaThe number and sequence of the Mannuronate and Glucuronate residues shown above vary in the naturally occurring alginate. The water molecules associated with the alginate molecule are not shown in the above structural formula.
Formula weightStructural unit : 198.11 (theoretical), 222 (actual average)Macromolecule : 10,000 – 600,000 (typical average)
AssayYields, on the dried basis, not less than 18.0% and not more than 21.0% of carbon dioxide (CO2), equivalent to not less than 90.8% and not more than 106.0% of sodium alginate (C6H7 NaO6)n.
DESCRIPTIONWhite to yellowish brown filamentous, grainy, granular or powdered forms
FUNCTIONAL USESStabilizer, thickener, gelling agent, emulsifier
SolubilityDissolves slowly in water, forming a viscous solution; insoluble in ethanol and ether
Precipitate formation with calcium chlorideTo a 0.5% solution of the sample in sodium hydroxide TS add one-fifth of its volume of a 2.5% solution of calcium chloride. A voluminous, gelatinous precipitate is formed. This test distinguishes sodium alginate from gum arabic, sodium carboxymethyl cellulose, carrageenan, gelatin, gum ghatti, karaya gum, carob bean gum, methyl cellulose and tragacanth gum.
Precipitate formation with ammonium sulphateTo a 0.5% solution of the sample in sodium hydroxide TS add one-half of its volume of a saturated solution of ammonium sulfate. No precipitate is formed. This test distinguishes sodium alginate from agar, sodium carboxymethyl cellulose, carrageenan, de-esterified pectin, gelatin, carob bean gum, methyl cellulose and starch.
Test for alginatePasses test
Test for sodiumPasses test
Loss on dryingNot more than 15% (105o, 4 h)
Water-insoluble matterNot more than 2% on the dried basisSee description under TESTS
ArsenicNot more than 3 mg/kg (Method II)
LeadNot more than 5 mg/kgDetermine using an atomic absorption technique appropriate to the specified level. The selection of sample size and method of sample preparation may be based on the principles of the method described in Volume 4, “Instrumental Methods.”
Microbiological criteriaTotal plate count: Not more than 5,000 colonies per gram.Initially prepare a 10-1 dilution by adding a 50 g sample to 450 ml of Butterfield’s phosphate buffered dilution water and homogenizing in a high speed blender.Yeasts and moulds: Not more than 500 colonies per gramColiforms: Negative by testSalmonella: Negative by test
Water-insoluble matterDisperse 2 g of the sample, weighed to the nearest 0.1 mg, in 800 ml of water in a 2,000-ml flask. Neutralize to pH 7 with sodium hydroxide TS and then add 3 ml in excess. Add 40 ml of hydrogen peroxide solution containing 30% by weight H2O2, cover the flask and boil for 1 h with frequent stirring. Filter while hot through a tared Gooch crucible provided with a glass fibre filter (2.4 cm, No 934 AH, Reeve Angel & Co, Clifton, N.Y.,USA, or equivalent). If slow filtration is caused by high viscosity of the sample solution, boil until the viscosity is reduced enough to permit filtration. Wash the crucible thoroughly with hot water, dry the crucible and its contents at 105o for 1 h, cool and weigh. Calculate as percentage of the dry weight.
METHOD OF ASSAYProceed as directed under Carbon Dioxide Determination by Decarboxylation. Each ml of 0.25 N sodium hydroxide consumed is equivalent to 5.5 mg of carbon dioxide (CO2) or 27.75 mg of sodium alginate (equivalent weight 222).