ALGIN

           ALGIN

Synonym :Sodium alginate, Sodium polymannuronate .

Biological Source :

Sodium alginate is the sodium salt of alginic acid. Alginic acid is a polyuronic acid composed of reduced mannuronic and glucoronic acids, which are obtained from the algal growth of the species of family Phaeophyceae. The common species are Macrocystispyrifera, Laminariahyperborea, Laminaria-digitata and Ascohyllumnodosum. It is purified carbohydrate extracted from brown sea(algae) by treatment of dilute alkali.

Geographical Source

Seaweeds are found in Atlantic and Pacific Oceans, particularly in Coastal lines of Japan, theUSA, Canada, Australia, and Scotland. In India, it is found near the Coast of Saurashtra. The USA and the UK are largest production of Algin.

History

It was discovered by Stanford in 1880. The commercial production of Algin first began in 1929 in USA. Since then it is produced in the UK, France, Norway and Japan. The present total Algin production is estimated to be more than 15,000 tonnes per annum.

Description

 Colour                        -           White to buff coloured powder

 Odour                         -           Odourless

Taste                           -           Tasteless

It is available either as a coarse or fine powder. It loses about 20 per cent of its weight on drying. Sodium alginate is incompatible with calcium salts, phenyl mercuric acetate and nitrate, crystal violet, alcohol in the concentrations above 5 per cent and heavy metals. It is also precipitated below pH 3.0.

Alginic acid is a linear co-polymer. It contains D-mannopyranosyluronic acid linked with L-glucopyranosyluronic acid units.

It is readily soluble in water forming viscous colloidal solution and insoluble in alcohol, ether, chloroform and strong acids. 1 per cent solution of gum at 20°C may have a viscosity in the range of 20 - 400 centipoises.

Uses :

1.    High and medium viscosity grades of sodium alginate are used in the preparation of paste, Creams and for thickening and stabilizing emulsions.

2.    It is a good suspending and thickening agent, but a poor emulsifying agent.

3.    It is used as binding and disintegrating agent in tablets and lozenges.

4.    In food industry, it is used for the preparation of jellies, ice cream, etc.

5.     It is also used in textile industry.

6.    For pharmaceutical purposes, when desired, it is sterilized by heating in an autoclave.

7.    The solution of sodium alginate should not be stored in metal containers. It is preserved by the additionof 0.1 per cent of chloroxylenol, chlorocresol, benzoic acid or parabenes. Potassium, aluminum and calcium alginates are also used medicinally.