'' being farmed for iota-carrageenan in an off-bottom cultivation in Tanzania Although carrageenans were introduced on an industrial scale in the 1930s, they were known to be used in
China since around 600 BCE(where
Gigartina was used) and in
Ireland around 400 CE. Carrageenan derived from
Eucheuma spp. (today one of the main cultivated sources of carrageenan), known as
gusô or
tambalang in the
Visayan languages, has also been traditionally used as food in the
Philippines. They were first recorded in the
Diccionario De La Lengua Bisaya, Hiligueina y Haraia de la isla de Panay y Sugbu y para las demas islas (c.1637) of the
Augustinian missionary
Alonso de Méntrida . In the book, Méntrida describes gusô as being cooked until it melts, and then allowed to congeal into a sour dish. The most commonly used sources are
Eucheuma cottonii,
Kappaphycus alvarezii, and
Eucheuma spinosum, which together provide about three-quarters of the world production. These grow from the sea surface to a depth of about . The seaweed is normally grown on nylon lines strung between bamboo floats, and it is harvested after three months or so, when each plant weighs approximately . After harvest, the seaweed is dried, baled, and sent to the carrageenan manufacturer. There the seaweed is ground, sifted to remove impurities such as
sand, and washed thoroughly. After treatment with hot
alkali solution (e.g., 5–8%
potassium hydroxide), the
cellulose is removed from the carrageenan by
centrifugation and
filtration. The resulting carrageenan solution is then concentrated by
evaporation. It is dried and ground to specification. There are three types of industrial processing:
Semi-refined This is only produced from
E. cottonii or
E. spinosum. The raw weed is first sorted and crude contaminants are removed by hand. The weed is then washed to remove salt and sand, and then cooked in hot alkali to increase the gel strength. The cooked weed is washed, dried, and milled.
E. spinosum undergoes a much milder cooking cycle, as it dissolves quite readily. The product is called semi-refined carrageenan, Philippines natural grade, or, in the U.S., it simply falls under the common carrageenan specification. cleaned and washed seaweed ↓ extraction ↓ coarse filtration → seaweed residue ↓ fine filtration → used filter aids ↓ ↓-------------- concentration --------------↓ preparation with KCl preparation with alcohol ↓ ↓ gel pressing alcohol recovery ↓ ↓ drying drying ↓ ↓ milling milling ↓ ↓ blending blending ↓ ↓ gel refined carrageenan refined carrageenan
Refined The essential difference in the refining process is that the carrageenan is first dissolved and filtered to remove cell wall debris. The carrageenan is then precipitated from the clear solution, either by isopropyl alcohol (propan-2-ol) or by potassium chloride.
Mixed processing A hybrid technology in which seaweed is treated heterogeneously as in the semirefined process exists, but alcohol or high salt levels are used to inhibit dissolution. This process is often used on South American seaweeds and gives some of the cost benefits of semirefined processing, while allowing a wider range of seaweeds to be processed, however, the naturally low cellulose levels in some South American seaweeds allow them to be heterogeneously processed and still be sold under the EU refined specification.
Grades There are two basic grades of carrageenan, refined (RC) and semi-refined (SRC). The latter is also known as "processed
Eucheuma seaweed" (PES) and "Philippine natural grade" (PNG) carrageenan. In the European Union, refined carrageenan is designated by the
E number E-407 and semi-refined carrageenan as E-407a. Refined carrageenan has a 2% maximum for acid-insoluble material and is produced by alcohol precipitation or potassium chloride gel press process. and is produced in a less complex process. Indonesia, the Philippines, and Chile are three main sources of raw material and extracted carrageenan. == Uses and applications ==