This brown algae that grows in the wild, is harvested by hand or mechanically, and dried. The alginic acids are converted into soluble sodium salt and extracted. These solutions are purified through filtration and decantation. There are three different methods to isolate the products:
- Precipitation as calcium alginate, outgrowth of the calcium ions with acids, neutralisation of the alginic acids to the desired alginate.
- Precipitation of the alginic acids with sulphuric acids, neutralisation of alginic acid to the desired alginate.
- Precipitation of sodium alginate with alcohol.
From the chemical point of view, alginate polysaccharides are from the salts of mannuronic and guluronic acids. The ratio of the mannuronic to the guluronic acids and the structure of the polysaccharides depend on the nature of the algae used as raw material. The properties of the alginates manufactured in this manner differ in accordance with the raw materials used.
Polygal obtains sodium alginates mainly from China.