Carrageenan production goes back many decades and only recently, with the introduction of new weed sources, as there been any major developments in the processes involved. There are four basic processes used for the production of carrageenan. For the sake of convenience we will refer to these as:
- Alcohol Precipitation
- KCl Precipitation or gel press
- Danisco process
- Semi refined
The traditional process for the production of carrageenan is the alcohol precipitation process. It has the major advantage of being able to handle any type of seaweed source and hence can produce any type of carrageenan. The major drawback of this type of processing is the cost. The extra capital cost involved in the installation of flameproof equipment and the added equipment needed to re distill the large volumes of alcohol required make it a very expensive process. However it is the only commercial method of manufacturing lambda carrageenan, which is very soluble. Another advantage is the ability to use south American weed stocks such as Gigartina which can be very cost effective due to their high yield.
In recent years Alcohol precipitation has been declining and one of the processes that has taken its place is the gel press or KCl precipitation process. This technology comes from agar processing and is essentially identical to the manner in which agar is made from Gracillaria type weed stocks. Kappaphycus species have a very high kappa carrageenan content and when purified by filtration it is then possible to precipitate the carrageenan using potassium chloride, generally this forms a large jelly like mass that can be pressed to remove water. The pressed cake can then be dried and milled as usual. The great advantage of this process is that you have produced a refined product without incurring the extra costs of the alcohol recovery. On the downside the process only works with Kappaphycus species and can only make kappa type carrageenan gels. This process has had great succession the large Asian dessert jellies market.
There are two processes that aim to cheapen the production of carrageenan by not going to a highly dilute solution and then precipitating but applying a slurry process. The most important of these is the semi refined process which became possible with the farming of Kappaphycus species. The second is a compromise process developed by Danisco especially for treating south American species but would work on most weed types.
The semi refined process developed originally to produce a high gel strength, cheap carrageenan for use in the petfood industry. It has since developed into the fastest growing carrageenan technology and in conjunction with gel pressing has been the major cause of the decline and closure of many alcohol precipitation plants. In a semi refined process seaweed, either Kappaphycus or Eucheuma species, is first washed. The washed weed is then treated in a hot alkali mix with a very high potassium level. Many people use 5-8% potassium hydroxide. If the cooking temperature is kept below 80oC (for Kappaphycus) then the seaweed does not dissolve and the mu to kappa conversion is completed with the carrageenan still within the seaweed. The hot alkali and subsequent washing removes residual minerals, proteins and fats leaving behind the converted carrageenan and some residual cellulose from the cell walls. Hence semi refined carrageenan always contains residual cellulose and will never be clear. Semi refined carrageenan has experienced strong growth in the meats industry and in the dairy industry where clarity is not an issue. the main advantage of semi refined carrageenan is the low cost although it has been claimed that semi refined products are actually superior to refined in meat processing (Philp et al, 1998).
Danisco have a propriety process that is very similar to the semi refining process. In this process the seaweed is alkali treated in an alcohol slurry. Although this is not has cheap as the semi refining process it does allow the treatment of a wide variety of weed types.
The legal position was fought over by the large western companies trying to stop its use and the Asian manufacturers trying to get it accepted on a par with traditional products. According to FDA regulations semi refined carrageenan is know accepted as carrageenan and there is not legal distinction. EU regulations are different and semi refined carrageenan is allowed as its own e number (E407a) under the name Processed Eucheuma Seaweed (PES). The distinction is drawn on the level of residual cellulose in the product. Ironically the Danisco process is often used to process Gigartina type seaweeds but due to the natural low level of cellulose in the seaweed it is legally classified as refined in the EU despite being processed in a process almost identical to semi refining.
Further information on carrageenan structure, sources, synergy and protein interaction can be accessed using the arrows in the Further Reading box below.