Calcium alginate

Prepared at the 49th JECFA (1997)
superseding specifications prepared at the 44th JECFA (1995),
published in FNP 5 2 Addendum 3 (1995)

SYNONYMS	INS No. 404
DEFINITION	Calcium alginate is the Calcium salt of alginic acid.
C.A.S. number	9005-35-0
Chemical formula	(C6H7Ca1/2O6)n
Structural formula	Structural formula from Phillips, Wedlock and Williams: Gums and Stabilizers for the Food Industry 5 (1990) by permission of Oxford University Press. The number and sequence of the Mannuronate and Glucuronate residues shown above vary in the naturally occurring alginate. The associated water molecules are not shown.
Formula weight	Structural unit:	195.16 (theoretical)
		219 (actual average)
	Macromolecule:	10,000 - 600,000 (typical average)
Assay	Not less than 18.0% and not more than 21.0% of carbon dioxide (CO2), equivalent to not less than 89.6% and not more than 104.5% of calcium alginate (C6H7Ca1/2O6)n on the anhydrous basis.
DESCRIPTION	Occurs as white to yellowish brown filamentous, grainy, granular and powdered forms
FUNCTIONAL USES	Stabilizer, thickener, gelling agent, emulsifier
CHARACTERISTICS
IDENTIFICATION
Solubility	Insoluble in water and ether; slightly soluble in ethanol; slowly soluble in solutions of sodium polyphosphate, sodium carbonate, and substances that combine with calcium ions.
Precipitate formation with calcium chloride
	Passes test See description under TESTS
Precipitate formation with ammonium sulfate
	Passes test See description under TESTS
Test for alginate	Passes test See description under TESTS
Calcium	Passes test
PURITY
Loss on drying	Not more than 15% (105°, 4h)
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
Microbiological criteria	Total 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 gram Coliforms: Negative by test Salmonella: Negative by test
TESTS
IDENTIFICATION TESTS
Precipitate formation with calcium chloride
	To 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 calcium 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 sulphate
	To 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 calcium alginate from agar, sodium carboxymethyl cellulose, carrageenan, de-esterified pectin, gelatin, carob bean gum, methyl cellulose and starch.
Test for alginate	Dissolve as completely as possible 0.01 g of the sample by shaking with 0.15 ml of 0.1 N sodium hydroxide and add 1 ml of acid ferric sulfate TS. Within 5 min, a cherry-red colour develops that finally becomes deep purple.
METHOD OF ASSAY	Proceed as directed under Carbon Dioxide Determination by Decarboxylation in the General Methods. Each ml of 0.25 N sodium hydroxide consumed is equivalent to 5.5 mg of carbon dioxide (CO2) or 27.38 mg of calcium alginate (equivalent weight 219).