E 400 ALGINIC ACID

Commission Directive 98/86/EC

Definition Linear glycuronoglycan consisting mainly of β-(1-4) linked D-mannuronic and α-(1-4)linked L-guluronic acid units in pyranose ring form. Hydrophilic colloidal carbohydrate extracted by the use of dilute alkali from natural strains of various species of brown seaweeds (Phaeophyceae)

Einecs 232-680-1

Chemical formula (C6H8O6)n

Molecular weight 10,000 - 600,000 (typical average)

Assay Alginic acid yields, on the anhydrous basis, not less than 20 % and not

more than 23 % of carbon dioxide (CO2), equivalent to not less than 91 % and not more than 104,5 % of alginic acid (C6H8O6)n (calculted on equivalent weight basis of 200)

Description Alginic acid occurs in filamentous, grainy, granular and powdered

forms. It is a white to yellowish brown and nearly odourless

Identification

A. Solubility Insoluble in water and organic solvents slowly soluble in solutions of sodium carbonate, sodium hydroxide and trisodium phosphate

B. Calcium chloride precipitation test

To a 0,5 % solution of the sample in 1 M sodium hydroxide solution, add one fifth of its volume of a 2,5 % solution of calcium chloride. A voluminous, gelatinous precipitate is formed. This test distinguishes alginic acid from acacia gum, sodium carboxymethyl cellulose, carboxymethyl starch, carrageenan, gelatin, gum ghatti, karaya gum, locust bean gum, methyl cellulose and tragacanth gum

C. Ammonium sulphate precipitation test

To a 0,5 % solution of the sample in 1 M sodium hydroxide solution, add one half of its volume of a saturated solution of ammonium sulphate. No precipitate is formed. This test distinguishes alginic acid from agar, sodium carboxymethyl cellulose, carrageenan, de-esterified pectin, gelatin, locust bean gum, methyl cellulose and starch

D. Colour reaction

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 sulphate solution. Within 5 minutes, a cherry-red colour develops that finally becomes deep purple

Purity

pH of a 3 % suspension Between 2,0 and 3,5

Loss on drying Not more than 15 % (105°C, 4 hours)

Sulphated ash Not more than 8 % on the anhydrous basis

Sodium hydroxide (1 M solution) Not more than 2 % on the anhydrous basis insoluble matter

Arsenic Not more than 3 mg/kg

Lead Not more than 5 mg/kg

Mercury Not more than 1 mg/kg

Cadmium Not more than 1 mg/kg

Heavy metals (as Pb) Not more than 20 mg/kg

Total plate count Not more than 5 000 colonies per gram

Yeast and moulds Not more than 500 colonies per gram

E. coli Negative in 5 g

Salmonella spp. Negative in 10 g