E406 AGAR - EU Specification
Commission Directive 98/86/EC
Synonyms Gelose
Japan agar
Bengal, Ceylon, Chinese or Japanese isinglass
Layor Carang
Definition
Chemical name Agar is a hydrophilic colloidal polysaccharide consisting mainly of D-galactose units. On about every tenth D-galactopyranose unit one of the hydroxyl groups is esterified with sulphuric acid which is neutralised by calcium, magnesium, potassium or sodium. It is extracted from certain natural strains of marine algae of the families Gelidiaceae und Sphaerococcaceae and related red algae of the class Rhodophyceae
Einecs 232-658-1
Assay The threshold gel concentration should not be higher than 0,25 %
Description Agar is odourless or has a slight characteristic odour. Unground agar usually occurs in bundles consisting of thin, membranous, agglutinated strips, or in cut, flaked or granulated forms. It may be light yellowish- orange, yellowish-grey to pale yellow, or colourless. It is tough when damp, brittle when dry. Powdered agar is white to yellowish-white or pale yellow. When examined in water under a microscope, the agar appears granular and somewhat filamentous. A few fragments of the spicules of sponges and a few frustules of diatoms may be present. In chloral hydrate solution, the powdered agar appears more transparent than in water, more or less granular, striated, angular and occasionally contains frustules of diatoms. Gel strength may be standardised by the addition of dextrose and maltodextrines or sucrose
Identification
A. Solubility Insoluble in cold water; soluble in boiling water
Purity
Loss on drying Not more than 22 % (105 °C, 5 hours)
Ash Not more than 6,5 % on the anhydrous basis determined at 550 °C
Acid-insoluble ash (insoluble in approximately Not more than 0,5 % determined at 550 °C on the anhydrous basis 3N Hydrochloric acid)
Insoluble matter (in hot water) Not more than 1,0 %
Starch Not detectable by the following method: to a 1 in 10 solution of the
sample add a few drops of iodine solution. No blue colour is produced
Gelatin and other proteins Dissolve about 1 g of agar in 100 ml of boiling water and allow to cool of about 50 °C. To 5 ml of the solution add 5 ml of trinitrophenol solution (1 g of anhydrous trinitrophenol/100 ml of hot water). No turbidity appears within 10 minutes
Water absorption Place 5 g to agar in a 100 ml graduated cylinder, fill to the mark with water, mix and allow to stand at about 25 °C for 24 hours. Pour the contents of the cylinder through moistened glass wool, allowing the water to drain into a second 100 ml graduated cylinder. Not more than 75 ml of water is obtained
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