The most important processed seaweed products in Indonesia are the hydrocolloids agar and carrageenan. The following chapter gives an overview about the raw material which is used for the carrageenan production, the processing technologies of carrageenan and their applications.
Raw Material For Carrageenan Production
The original source of carrageenan was the red seaweed Chondrus crispus collected from natural resources along the west coasts in Europe and the east coast provinces of Canada. As the carrageenan industry expanded, the demand for raw material began to strain the supply from natural resources, although Chondrus had been supple-mented by species of Gigartina from Spain and especially Chile.
The introduction of cultivation of species of Eucheuma in the Philippines during the 1970s provided the carra-geenan industry with a much enhanced supply of raw material. A further advantage of this cultivated material was that one species contained almost exclusively a particular type of carrageenan (kappa-carrageenan) while a second species contained predominantly a second type (iota-carrageenan), each type having its own particular applications. Chondrus and Gigartina contains a mixture of two types (kappa and lambda) that could not be separated during commercial extraction. Today most of the raw material comes from the two Eucheuma species originally cultivated in the Philippines, but their cultivation has now spread to some other warm-water countries especially Indonesia where the natural conditions are most favorable.
Current Processing Technologies Of Carrageenan
According to the production process, there is a differentiation between refined and semi-refined carrageenan. Refined carrageenan is the original carrageenan. For many years it was the only carrageenan permitted in food products.
The main difference between refined carrageenan (RC) and semi-refined carrageenan (SRC) is that SRC contains the cellulose that was in the original seaweed while in refined carrageenan this has been removed by filtration during the processing. Refined carrageenan will therefore give a clear solution, while PNG gives a cloudy solution limiting the applications of SRC. For both products the seaweed is washed to remove sand, salts and other foreign matter.
Production of refined carrageenan
After the seaweed has been cleaned, for refined carrageenan it is then heated with water containing an alkali for several hours. This step is necessary to extract the carrageenan and at the same time increasing gel strength in the final product. The seaweed that does not dissolve is removed by centrifugation or a coarse filtration, or a combina-tion. The solution is then filtered again in a pressure filter using a filter aid in order to ensure complete removal of any insoluble particles.
Then the dissolved carrageenan has to be recovered. There are two methods for isolating it. Traditionally,
an alcohol-precipitation method is generally used as carrageenan is insoluble in high-alcohol concentrations. This method has the advantage that it can be used for all types of carrageenan.
Another method similar to the method used for making agar was later applied also to the refined carrageenan production. Therefore, some agar processors in Indonesia are now using their equipment and similar techniques to produce refined kappa carrageenan as well. This gelling method is most suitable for kappa carrageenan. The gel is mainly dehydrated by squeezing as for agar. But it could also be recovered with a freeze-thaw process.
The gel method relies on the ability of kappa carrageenan to form a gel with potassium salts. The gel may be formed in various ways. The most common method is to force water out of the gel by applying pressure to it, using similar equipment to that used for agar. After squeezing for several hours the sheets of gel are chopped, dried in a hot air dryer and milled to an appropriate particle size. Inevitably, with the gel method the product contains some potassium chloride.
Production of semi-refined carrageenan
Also for the production of semi-refined carrageenan, the seaweed needs to be washed before further processing. For the production of SRC the carrageenan is never actually extracted from the seaweed. The principle is rather to wash everything out of the seaweed that will dissolve in alkali and water and leave the carrageenan and other insoluble matter behind. This insoluble residue, consisting largely of carrageenan and cellulose, is then dried and sold as SRC. Because the carrageenan does not need to be recovered from the solution, the process is much shorter and cheaper.
In the production of SRC the washed and cleaned seaweed is heated in an alkaline solution of potassium hydroxi-de for about two hours in order to increase the gel strength of the carrageenan in the seaweed and at the same time dissolve any soluble protein, carbohydrate and salts without dissolving the carrageenan. After the alkali treatment and water washing, the product is chopped and dried in a closed dryer which will keep the bacterial count low enough to make a human-food grade product.
Alkaline treated Eucheuma cottonii seaweed not produced according to the requirements for food applications is normally referred to as ATC. Often it is simply sold as chips (ATCC) which are typically used for the extraction of refined carrageenan, for canned pet food or non-food applications.
Aplications Of Carrageenan
Carrageenan is one of the most diversified food additives due to the broad range of gelling and emulsifying properties – ranging from a soft elastic to a very brittle gel – and the ability to substitute to a large degree both gelatin and agar.
In Europe, both refined and SRC are permitted in human food:
- Refined carrageenan (RC) is labeled “carrageenan” and E-407
- Semi-refined carrageenan (SRC) is labeled “processed Eucheuma seaweed” or “PES”, and E-407a
Some years ago, the FDA declared SRC suitable for the use in human food in the USA and to be labelled as “carrageenan” with the same status as that of the refined carrageenan product.
Carrageenan is used in processed foods for stabilization, thickening and gelation driven by the consumers’ need for convenience, appealing food textures, advances in food processing, and new food products. It is used worldwide to enhance ice creams eliminating formation of ice crystals, chocolate milk, custards, cheeses, jellies, confectionary products, meat and for clarification of beer and wine.
Carrageenan has a high reactivity with a range of materials including and most importantly milk proteins so it can be efficient at low concentrations in dairy products to prevent fractionation of milk constituents. A major applicati-on is in chocolate milk where carrageenan is able to keep the cocoa particles in suspension.
Today, processed meat and poultry products offer the largest application for carrageenan worldwide with its many properties such as water binding and retention, fat substitution, control of syneresis and dehydration and enhancement of juiciness. Improved slice ability is especially important in high-speed slicers.
Kappa carrageenan obtained from the seaweed E. cottonii needs potassium salt to gel. It then results in brittle gels. Kappa carrageenan is soluble in hot water and shows synergistic effect with other food additives like locust bean gum, guar gum and xanthan.
Iota carrageenan gels most strongly with calcium salts, resulting in elastic gels with no syneresis. The gels furthermore freeze-thaw stable. Iota carrageenan is obtained from the seaweed E. spinosum
Carrageenan is also widely used in the canned pet food industry and in some non-food applications such as toothpaste and air fresher gels.