COMMISSION REGULATION (EU) No 231/2012 of 9 March 2012
Synonyms
Gelose; Kanten, Bengal, Ceylon, Chinese or Japanese isinglass; Layor Carang
Definition
Agar is a hydrophilic colloidal polysaccharide consisting mainly of galactose units with a regular alternation of L and D isomeric forms. These hexoses are alternately linked with alpha-1,3 and beta-1,4 bonds in the copolymer. 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 strains of marine algae of the families Gelidiaceae and Gracilariaceae and relevant red algae of the class Rhodophyceae
Einecs: 232-658-1
Chemical name:
Chemical formula:
Molecular weight:
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 yellowishorange, 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, agar powder appears more transparent. 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
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 3N Hydrochloric acid): Not more than 0.5 % determined at 550°C on the anhydrous basis
Insoluble matter (after stirring for 10 minutes 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
Microbiological criteria
Total plate count: Not more than 5 000 colonies per gram
Yeast and moulds: Not more than 300 colonies per gram
Escherichia coli: Absent in 5 g
Salmonella spp.: Absent in 5 g