Seaweeds supply three sources of raw material, agar, alginates and carrageenan which have a broad range of industrial uses.
Due to the high vitamin and mineral salt content of some seaweeds, they are also used for direct human consumption, as livestock feed supplements as soil fertilizers.
Agar
Agar has particular gelling characteristics whose applications are increasing worldwide:
In the human food industry agar is used mainly as a gelling agent and in a secondary way as a stabilizing agent and for controlling viscosity. The most important applications of agar in the food industry are in confectionery, in marmalade production, in baking as an icing, in fruit jelly preparations, in yoghurt, in the meat industry to reduce the fat content of soft boiled sausages, in canned products and as mitsumame production (fruit flavoured agar gel cubes) in Japan.
Agar is used to produce casting moulds in sculpture, archaeology, dental moulds and other works where precise reproduction is essential.
Agar is also used in the pharmaceutical industry for laxatives, to stabilize cholesterol solutions, and as an anti-rheumatic treatment.
In the agricultural industry, agar is used for cellular cultivation and agarose has been is employed in biochemical technology and genetic engineering.
Agar is marketed pure and world agar production has been estimated to be between 7,000 to 10,000 tonnes of which half is from Gracilaria species. Japan is the top producer and consumer but still depends on imports to meet national demand.
The most important agar manufacturers are Japan accounting for 37 % of total production in 1984 followed by Spain (13 %) and Chile (12 %). Other important producers include South Korea, Morocco and Portugal.
Marketing of industrial food grade agar is generally made through trading companies operating from Japan, Hamburg, London and New York. The world market for bacteriological agar and agarose is small in relation to the food grade market.
Alginates
Alginates are used in the textile industry as thickeners for pastes containing dye. It has been estimated that the textile industry accounts for 50 % of world demand for alginates. The second most important use of alginates (30 % of world demand) is in the food industry mainly as a thickening and gelling agent for sauces, syrups and increasingly, for restructured meat, fish and fruit products. Alginates are also used as a stabilizer for ice-cream.
Alginates are also used in biochemical applications, in the paper industry for surface sizing such as glosses and in starch adhesives, as coatings on welding rods, and in pharmaceutical applications as a disintegrating agent for tablets, to increase viscosity in liquid medicines, diet foods and dental impression compounds and in the fish feed industry as a binder.
The world market for alginates has been estimated at 20,000 to 24,000 tonnes per annum. In 1981, it was estimated that there were 17 alginate factories in 9 different countries (excluding the People's Republic of China). The two largest producers are in the USA and the UK, accounting for approximately 70 % of the world's alginate production. Other producers in order of importance are Norway, Japan and France.
Carrageenan
Carrageenan are water-soluble gums which are used to gel, thicken or suspend. Major applications of carrageenan are in the food industry particularly in dairy applications such as pasteurized milk products, sterilized milk products and milk desserts. The food industry accounts for approximately 70 % of total world demand for carrageenan. Carrageenan is also used in the toothpaste industry as a binding agent, as a gelling agent in pet foods, and in air freshener gels.
Two types of carrageenan are currently available - extractive and semi-refined. Semi-refined carrageenan requires less energy and uses Eucheuma sp. as an input. The market growth for this product is expected to be greater than that for extractive carrageenan which has shown signs of levelling off.
Other uses
Seaweeds are used for direct human consumption particularly in Japan, the Korean peninsula and China. Species of Laminaria, Undaria and Hizikia are the major seaweeds used and are usually sold as dried products. These are used in soups, as a vegetable as seasoning for rice dishes and as snack foods. Some seaweeds are eaten fresh as a salad vegetable or a garnish. Species of Eucheuma, Caulerpa and Gracilaria are eaten fresh. Japan has the highest per capita consumption of seaweed as food.
Some species of seaweeds are dried and used as soil fertilizers in western Europe and south-east Asia because of their high mineral salt content. Ulva, Sargassum and Turbinaria species are the most important. In addition, in some western European countries such as France, Norway and the U.K. seaweeds have been used as livestock feed supplements, because some species such as Ulva, Sargassum, and Ascophyllum have a high vitamin content.
