Algae and algal products, such as agar, carragenin furcellaran and algins, have been used by humans for various purposes from time immemorial. For instance, during the fifteenth and sixtennth centuries soda was extracted from algae for use in glass manufacture and a century ago algae were the predominant source of raw material for iodine production.
Seventy-eight species of algae produce agents of the group geloses, which includes agar. Agar is now produced in e.g. the United States, Australia and New Zealand and since the fifteenth century in Japan. It is well known as a solidifying agent in bacteriological culture media, and is also used in dentistry, cosmetics and medicines (it can be used to assist slimming and as a laxative and to aid the healing of wounds). It is used in meat, fish and poultry canning and can be seen as a thickening agent in desserts, as a clarifying agent in beer and wine production and can even function as a wire-drawing lubricant.
Similarly, a substance extracted from Irish moss, or jelly moss, was formerly used to treat diarrhoea, gastric ulcer and cystitis. It is now harvested for use of its gelatinous substance (carragenan) for curing leather, as suspending and emulsifying agent in pharmaceuticals, food products (e.g. for stabilization of foam and as clarifying agent in beer and honey) and in cosmetics and in technical products such as shoe polish.
A red alga yields the substance furcellaran which is important in jam making and another related substance is used as a glue.
Brown algae are the source of fuciodan and laminaran which have medical use, as anti-coagulants, and of mannitol which is a valuable nutrient for diabetics. These algae also yield alginic acid, the salts of which (alginates) have a widespread use.
Alginates is used in e.g. textiles (fibres), cosmetic, pharmaceutical, paper and chemical (paints, films, plastics) industries.