CARRAGEENAN

There are several carrageenans, differing in their chemical structure and properties, and therefore in their uses. The carrageenans of commercial interest are called iota, kappa and lambda.
Their uses are related to their ability to form thick solution or gels, and they vary as follows.

Iota	Elastic gels formed with calcium salts. Clear gel with no bleeding of liquid (no synaeresis). Gel is freeze/thaw stable.
Kappa	Strong, rigid gel, formed with potassium salts. Brittle gel forms with calcium salts. Slightly opaque gel, becomes clear with sugar addition. Some synaeresis.
Lambda	No gel formation, forms high viscosity solutions.

The carrageenan composition in red seaweeds differs from one species to another.

Chondrus crispus	mixture of kappa and lambda.
Kappaphycus alvarezii	mainly kappa.
Eucheuma denticulatum	mainly iota.
Gigartina skottsbergii	mainly kappa, some lambda.
Sarcothalia crispata	mixture of kappa and lambda.

7.1 Carrageenan production methods

There are two different methods of producing carrageenan, based on different principles.
In the original method - the only one used until the late 1970s-early 1980s - the carrageenan is extracted from the seaweed into an aqueous solution, the seaweed residue is removed by filtration and then the carrageenan is recovered from the solution, eventually as a dry solid containing little else than carrageenan. This recovery process is difficult and expensive relative to the costs of the second method.
In the second method, the carrageenan is never actually extracted from the seaweed. Rather the principle is to wash everything out of the seaweed that will dissolve in alkali and water, leaving the carrageenan and other insoluble matter behind. This insoluble residue, consisting largely of carrageenan and cellulose, is then dried and sold as semi-refined carrageean (SRC). Because the carrageenan does not need to be recovered from solution, the process is much shorter and cheaper.

7.1.1 Refined carrageenan and filtered carrageenan

Refined carrageenan is the original carrageenan and until the late 1970s-early 1980s was simply called carrageenan. It is now sometimes called filtered carrageenan. It was first made from Chondrus crispus, but now the process is applied to all of the above algae.
The seaweed is washed to remove sand, salts and other foreign matter. It is then heated with water containing an alkali, such as sodium hydroxide, for several hours, with the time depending on the seaweeds being extracted and determined by prior small-scale trials, or experience. Alkali is used because it causes a chemical change that leads to increased gel strength in the final product. In chemical terms, it removes some of the sulphate groups from the molecules and increases the formation of 3,6-AG: the more of the latter, the better the gel strength. The seaweed that does not dissolve is removed by centrifugation or a coarse filtration, or a combination. The solution is then filtered again, in a pressure filter using a filter aid that helps to prevent the filter cloth becoming blocked by fine, gelatinous particles. At this stage, the solution contains 1-2 percent carrageenan and this is usually concentrated to 2-3 percent by vacuum distillation and ultrafiltration.

FIGURE 44
Sun drying semi-refined carrageenan (alkali treated K. alvarezii).

FIGURE 45
Flow chart for the production of refined carrageenan (after Porse, 1998).

The processor now has a clear solution of carrageenan and there are two methods for recovering it as a solid, both rather similar to those described previously for agar production. An alcohol-precipitation method can be used for any of the carrageenans. A gel method can be used for kappa-carrageenan only, and the gel can be dehydrated either by squeezing or by subjecting it to a freeze-thaw process.
In the alcohol method, isopropanol is added until all the carrageenan is precipitated as a fibrous coagulum that is then separated using a centrifuge or screen (a fine sieve). The coagulum is pressed to remove solvent and washed with more alcohol to dehydrate it further. It is then dried and milled to an appropriate particle size, 80 mesh or finer. For the process to be economic the alcohol must be recovered, both from the liquids and the dryer, and recycled.
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. For the freeze-thaw process it is convenient to form it as spaghetti-like pieces by forcing the carrageenan solution through fine holes into a potassium chloride solution. The fine "spaghetti" is collected and washed with more potassium chloride to remove more water, pressed to remove surplus liquid and then frozen. When allowed to thaw, separation of water occurs by synaeresis, the pieces are washed with more potassium chloride, chopped up and dried in a hot air dryer. Inevitably the product contains some potassium chloride. The alternative to freeze-thaw is to force water out of the gel by applying pressure to it, using similar equipment to that used for agar (Figure 10). After squeezing for several hours the sheets of gel are chopped, dried in a hot air dryer and milled to an appropriate particle size. Many agar processors are now using their equipment and similar techniques to produce kappa carrageenan as well.
Figure 45 summarizes the above processes.

7.1.2 Semi-refined carrageenan and seaweed flour

Semi-refined carrageenan (SRC) was the name given to the product first produced by the second method of processing noted in Section 7.1. This is the method in which the carrageenan is never actually extracted from the seaweed.
In the production of SRC, Kappaphycus alvarezii, contained in a metal basket, is heated in an alkaline solution of potassium hydroxide for about two hours. The hydroxide part of the reagent penetrates the seaweed and reduces the amount of sulphate in the carrageenan, increases the 3,6-AG so the gel strength of the carrageenan in the seaweed is improved. The potassium part of the reagent combines with the carrageenan in the seaweed to produce a gel and this prevents the carrageenan from dissolving in the hot solution. However, any soluble protein, carbohydrate and salts do dissolve and are removed when the solution is drained away from the seaweed. The residue, which still looks like seaweed, is washed several times to remove the alkali and anything else that will dissolve in the water. The alkali-treated seaweed is now laid out to dry; in hot climates, like the Philippines, usually on a large concrete slab (Figure 44). After about two days it is chopped and fed into a mill for grinding to the powder that is sold as SRC or seaweed flour.
The above process is summarized in Figure 46 (seaweed flour branch).
However, the seaweed flour is coloured, often has a high bacterial count and is not suitable for human consumption. Nevertheless it immediately found a large market in canned pet food because it is a good gelling agent and was so much cheaper than refined carrageenan. The temperatures used in the canning process destroy any bacteria so the high bacterial count in the SRC is not a problem. Sometimes the dried product is just chopped into pieces, not milled, and sold as a raw material to refined carrageenan processors. It is called alkali treated cottonii (ATC) or alkali treated cottonii chips (ATCC), or even simply cottonii chips. If this treatment is done in the country of origin of the seaweed, such as the Philippines or Indonesia, this means processors in Europe and United States of America have cheaper transport costs per tonne of carrageenan, compared with shipping dried seaweed. They have also left behind some waste products, which reduces their waste treatment costs.

FIGURE 46
Flow chart for the production of seaweed flour and PES/PNG carrageenans (after Bixler, 1996).

Kappaphycus alvarezii is used in this process because it contains mainly kappa carrageenan and this is the carrageenan that forms a gel with potassium salts. Iota-containing seaweeds can also be processed by his method, although the markets for iota carrageenan are significantly less than those for kappa. Lambda carrageenans do not form gels with potassium and would therefore dissolve and be lost during the alkali treatment.
The simplicity of the process means the product is considerably cheaper than refined carrageenan.
There is no alcohol involved that must be recovered, no distillation equipment to purify alcohol, no equipment for making gels, no refrigeration to freeze the gels, nor any expensive devices to squeeze the water from the gel.

7.1.3 Philippine natural grade (PNG) and processed Eucheuma seaweed (PES)

Producers in the Philippines developed a higher quality product, suitable for human consumption, by modifying the process just described for SRC.
After the alkali treatment and water washing, the product is chopped and treated with bleach to remove the colour (chopping improves penetration by the bleach, and bleach also helps to reduce the bacterial count). After washing to remove any bleach, the product is dried in a closed dryer. In this type of dryer, indirectly heated hot air passes up through a bed of the unground pieces or chips that are being carried through the dryer on a chain-type belt. This closed system dryer is usually sufficient to keep the bacterial count low enough to make a human-food grade product. If bacteria reduction is required, the dried chips can be milled and then washed with alcohol (ethanol) followed by vacuum evaporation to recover the alcohol. A simpler process is to treat the milled powder with superheated steam.
The above process is summarized in Figure 46 (PES/PNG carrageenan branch).
The product was originally called Philippine natural grade carrageenan (PNG).
Attempts to market this product as food grade in the United States of America and Europe resulted in strong opposition from the producers of refined carrageenan who did not wish to lose market share to this cheaper product. Eventually in the United States of America, the Food and Drug Administration declared it suitable for use in human food and to be labelled as "carrageenan", the same status as that of the refined product.
In Europe, both refined and PNG are permitted in human food, but carry different labels:

• refined carrageenan is labelled "carrageenan" and E-407; while
• Philippine natural grade is labelled "processed Eucheuma seaweed" or "PES", and E-407a.

So PNG and PES are the same grade of carrageenan.
The main difference between refined carrageenan and PNG is that PNG 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. Where clarity of a user's product is of no consequence, PNG is suitable.
For further details
Detailed information on any methods of carrageenan extraction are not easy to find. As Stanley (1987) said, they are closely guarded as trade secrets by the several manufacturers. Some information can be found in Stanley (1987), Stanley (1990) and Therkelsen (1993).

7.2 Carrageenan producers and distributors

A summary of the capacity of carrageenan producers according to their broad geographical location is given in Table 8, and the principal producers and distributors are listed in the next section.
TABLE 8
Carrageenan processors. Capacity in tonnes (2001)

	Alcohol process	Gel process	PES	Total	%	ATC 1
Europe	8 100	5 000	500	13 600	32
Americas	4 700	3 350	1 100	9 150	21
Asia-Pacific	2 000	8 280	9 900	20 180	47	16 000
Total	14 800	16 630	11 500	42 930		16 000

¹ ATC = Alkali treated cottonii or seaweed flour, used mainly for pet food.
Source: H. Porse, CP Kelco. ApS, 2002, pers. comm

7.2.1 Refined carrageenan producers and distributors

_________________________________
CP Kelco ApS
Ved Banen 16
4623 Lille Skensved
Denmark
Tel: [INT+45] + 5616 5616
Fax: INT+45] + 5616 9446
Website: www.cpkelco.com
_________________________________
Shemberg Marketing Corporation
corner Lapu-lapu and Osmena Boulevard
Cebu City
The Philippines
Tel: [INT+63] + (32) 346 0866
Fax: [INT+63] +(32) 346 1892; 346 0863
_________________________________
Shemberg Biotech Corporation
Carmen, Cebu City
The Philippines
Tel: [INT+63] + (32) 254 9380
Fax: [INT+63] + (32) 254 9388
_________________________________
Ingredients Solutions Inc.
PO Box 407
Searsport, ME 04974-0407
United States of America
Tel: [INT+1] + (207) 548 0074
Fax: [INT+1] + (207) 548 2921
_________________________________
Marcel Carrageenan Corporation
926 Araneta Avenue
Quezon City 1104
Philippines
Tel: [INT+63] + (2) 712 2631/2640/2841
Fax: [INT+63] + (2) 712 1989/5879
_________________________________
FMC Biopolymer
1735 Market Street
Philadelphia PA 19103
United States of America
Tel: [INT+1] + (215) 299 6000
Fax: [INT+1] + (215) 299 5809
Websites: www.fmc.com;
www.fmcbiopolymer.com
_________________________________
Degussa Texturant Systems
Lise-Meitner-St.34
85354 Freising
Germany
Tel: [INT+49] + (8161) 548 266
Fax: [INT+49] + (8161) 548 582
Website: www.texturantsystems.com
_________________________________
Danisco Cultor
Edwin Rahrs Vej 38
8220 Brabrand
Denmark
Tel: [INT+45] 89 43 50 00
Fax: [INT+45] 86 25 06 81
Website: www.daniscocultor.com
_________________________________
Rhodia Food
40, rue de la Haie-Coq
93306 Aubervilliers Cedex
France
Tel: [INT+33] 1 53 56 50 00
Fax: [INT+33] 1 53 56 55 55
Website: www.rhodiafood.com
_________________________________
Gelymar S.A.
Av. Pedro de Valdivia Norte 061
Providencia, Santiago
Chile
Tel: [INT+56] + 2 230 9400
Fax: [INT+56] + 2 232 1544
_________________________________
CEAMSA
"Les Gandaras", PO Box 161
36400 Porrino (Pontevedra)
Spain
Tel: [INT+34] + (986) 344 089
Fax: [INT+34] + (986) 336 621
Website: www.ceamsa.com
_________________________________
Hispanagar, S.A.
Avenida López Bravo, 98
Polígono de Villalonquejar
Apartado Postal 392
08080 Burgos
Spain
Tel: [INT+34] + (947) 298519
Fax: [INT+34] + (947)298518
Website: www.hispanagar.net
_________________________________
Ina Food Industry Co., Ltd.
574 Tsurumakicho, Waseda
Shijuku
Tokyo 162
Japan
Tel: [INT+81] + (3) 3235 8861
Fax: [INT+81] + (3) 3235 8863
_________________________________
Myeong Shin Chemical Ind. Co., Ltd.
439-13, Soju-Ri, Ungsang-Up,
Yangsan-gun, Kyeong-Nam,
The Republic of Korea
Tel: [INT+82] + (55) 389 1001
Fax: [INT+82] + (55) 389 0478
(Head Office and carrageenan factory)
_________________________________
Soriano S.A.
9 de Julio 745
9100 Trelew
PCIA Chubut
Argentina
_________________________________
Chuo Food Materials Co.Ltd
Osaka
Japan
Marine Science Co Ltd
Higashi-kanda Towa-building 6F, 2-3-3,
Higashi-kanda
Chiyoda-ku
Tokyo 101-0031 Japan
Tel: [INT+81] + (3) 3865 3485
Fax [INT+81] + (3) 3865 3450

7.2.2 PNG and PES and seaweed flour producers and distributors

_________________________________
Ingredients Solutions Inc.
PO Box 407
Searsport ME 04974-0407
United States of America
Tel: [INT+1] + (207) 548 0074
Fax: [INT+1] + (207) 548 2921
_________________________________
Marcel Carrageenan Corporation
926 Araneta Avenue
Quezon City 1104
The Philippines
Tel: [INT+63] + (2) 712 2631/2640/2841
Fax: [INT+63] + (2) 712 1989/5879
_________________________________
Shemberg Marketing Corporation
corner Lapu-lapu and Osmena Boulevard
Cebu City
The Philippines
Tel: [INT+63] + (32) 346 0866
Fax: [INT+63] + (32) 346 1892/0863
_________________________________
Quest International Philippines Corp.
Mactan Export Processing Zone,
G/F SFB Pt. 1,
Lapu-Lapu City
Cebu
The Philippines.
Tel: [INT+63] + (32) 340 0322/0319/0764
Fax: [INT+63] + (32) 340 0328/0324
_________________________________
FMC Corporation
Ouano Compound
Looc, Mandaue City
6014 Cebu
The Philippines.
Tel: [INT+63] + (32) 85097, 346 0882
Fax: [INT+63] + (32) 54098, 3461182/1187
_________________________________
Geltech Hayco, Inc.
2211 Taft Avenue
Metro Manila
The Philippines.
Tel: [INT+63] + (2) 521 3094, 571 306
Fax: [INT+63] + (2) 526 0591
_________________________________
TBK Manufacturing Corp.
Brgy 76, Hollywood, Nula-tula
Tacloban city
6500 Leyte
The Philippines
Tel: [INT+63] + (2) 727 6891
Fax: [INT+63] + (2) 725 5163
_________________________________
Iberagar S.A.
Estrada Nacional 10, km. 18
Coina
Portugal
Tel: [INT+35] + (121) 210 9252
Fax: [INT+35] + (121) 2109255
Website: www.iberagar.com
_________________________________
P.T. Surya Indoalgas Jln Kedungdoro - 60
Surabaya 60251
Indonesia
Tel: [INT+62] + (31) 548 2003
Jakarta office:
Tel: [INT+62] + (21) 564 7270
Fax: [INT+62] + (21) 564 9285
_________________________________
C.V. Cahaya Cemerlang
Jln S. Cerekang - 16(34)
Ujung Pandang
Indonesia
Tel: [INT+62] + (411) 31 53 58
Fax: [INT+62] + (411) 31 82 27
_________________________________
P.T. Gumindo Perkasa Industri
Wisma UIC, 2nd Floor
Jln Jend Gatal Kav 6-7
Jakarta 12930
Indonesia
Tel [INT+62] + (21) 520 0832
Fax: [INT+62] + (21) 529 60004
_________________________________
P.T. Asia Sumber Laut Indonesia
Jln Rajawali 64 K
Surabaya 60176
Indonesia
Tel: [INT+62] + (31) 357 7892
Fax: [INT+62] + (31) 357 7901
For further information about the Philippines contact:
Secretary General
Seaweed Industry of the Philippines
T.R. Martinez Bldg, 2nd Floor
Osmena Blvd
Cebu City,
The Philippines
Tel: [INT+63] + (32) 253 7433
Fax: [INT+63] + (32) 254 8780
For further details about Indonesia and other Indonesian companies contact:
Indonesian Seaweed Industry Association (APBIRI) at:
Asosiasi Pengusaha Budidaya dan Industri Rumput Laut Indonesia (APBIRI)
BPPT Lt. 13
Jl. MH Thamrin No. 8
Jakarta Pusat 10340
Indonesia
Tel: (62) 21 322430

7.3 Carrageenan uses

Before discussing uses, some explanations of the properties of carrageenans are necessary.
Both kappa and iota carrageenan form gels with potassium and calcium salts. Aqueous solutions of both carrageenans must be heated above 60°C for the carrageenan to dissolve, and after addition of the salt, the gel forms as the solution cools. For kappa, as little as 0.5 percent in water and 0.2 percent in milk is sufficient to form gels.
Kappa forms gels most strongly with potassium salts, followed by calcium salts. Potassium gives a rigid, elastic gel while calcium produces a stiff, brittle gel. Kappa gives the strongest gels of all carrageenans, but they are also the ones most likely to bleed (most subject to synaeresis). This liability can lessened in a couple of ways. If iota and lambda carrageenans are blended in with the kappa, bleeding can be reduced, so will also the rigidity and brittleness of the gel; however, the gel strength may also be lowered. Synaeresis can also be reduced by adding locust bean gum (obtained from the seeds of the carob tree (Ceratonia siliqua), growing in Spain, Italy, Cyprus, etc.). This gum also allows the amount of kappa to be reduced while still maintaining the same gel strength. The kappa can be reduced to one-third of the concentration that would be needed if no locust bean gum were used. The resulting gels are more resilient than those with kappa alone. As long as locust bean gum is cheaper than kappa there is also an economic advantage. However, the cost of locust bean gum can fluctuate depending on the harvest and demand.
Iota forms gels most strongly with calcium salts, followed by potassium salts - the reverse of kappa reactivities. Calcium gels are soft and resilient and are virtually free of bleeding. They can be frozen and thawed without destroying the gel. They show an unusual property for a gel: thixotropic flow; this means the gel can be stirred and it will flow like a thick liquid, but if left to stand it will gradually reform a gel.
A similar thixotropic behaviour is found with very low concentrations of kappa carrageenan in milk; a weak gel forms that is easily made to flow by shaking. The weak gel is strong enough to suspend fine particles in the milk, such as cocoa in chocolate milk.
Protein reactivity of carrageenans is an important property that is utilized in several applications. Carrageenan molecules carry negative charges; this is what enables them to combine with positively charged particles like the potassium found in potassium salts. They can also combine with positively charged proteins. Carrageenan will combine with the protein in milk (casein) to form a three-dimensional gel network. The exact nature of the interaction of proteins with carrageenans appears to be more complex than this simple explanation, and the interested reader can find more detail in the references suggested in Section 7.3.8.

7.3.1 Dairy products

The main applications for carrageenan are in the food industry, especially in dairy products.
Frequently, only very small additions are necessary, 0.01-0.05 percent. For example, kappa carrageenan (at 0.01-0.04 percent) added to cottage cheese will prevent separation of whey, and a similar amount added to ice cream also prevents whey separation that may be caused by other gums that were added to the ice cream to control texture and ice crystal growth. The cocoa in chocolate milk can be kept in suspension by addition of similar amounts of kappa; it builds a weak thixotropic gel that is stable as long as it is not shaken strongly. Dry instant chocolate mixes, to be mixed with water or milk, can have improved stability and mouth feel using lambda or a mixture of carrageenans.
Lambda or a mixture can also improve liquid coffee whiteners by preventing the separation of fat; these applications require 0.2-0.3 percent additions, but much smaller quantities will prevent fat separation in evaporated milks. Those small containers of UHT sterilized milk found in the refrigerators of some hotels may have kappa added to prevent fat and protein separation. Lambda or kappa may be added to natural cream to help maintain the lightness (incorporated air) if it is whipped. Many more uses in milk and dairy products can be found in the references below.

7.3.2 Water-based foods

With the appearance of bovine spongiform encephalopathy (BSE, or mad cow disease) and foot-and-mouth disease, efforts have been made to find suitable substitutes for gelatin. Gelatin jellies have long been favoured because they melt at body temperature, giving a smooth mouth feel and easy release of flavours. However, if they are stored for a day or two, they toughen and are less pleasant to eat. Gels made from iota carrageenan have the disadvantage of a high melting temperature, so they are not as smooth to eat as gelatin gels. They do not melt on hot days and do not require refrigeration to make them set, so these are advantages in hot or tropical climates, and a further advantage is that they do not toughen on storage. In the last two years there have been several claims by food ingredients companies for products, made from a mixture of hydrocolloids, that imitate the properties of gelatin. Carrageenan producers find that by combining various carrageenans with locust bean gum, konjac flour and starch, they can provide a variety of melting and non-melting gels and gel textures to meet the requirements of most of their clients. Long-life refrigerated mousse desserts, based on carrageenan and pectin rather than gelatin, are suitable for vegetarians and some ethnic groups.
Conventional fruit jellies are based on pectin and a high sugar content to help set the jelly. In a low- or non-calorie jelly the pectin must be replaced, and mixtures of kappa and iota have proved to be suitable. Fruit drink mixes to be reconstituted in cold water contain sugar (or aspartame), acid and flavour. Addition of lambda carrageenan gives body and a pleasant mouth feel. Sorbet is a creamy alternative to ice cream with no fat; use of a mixed kappa and iota together with locust bean gum or pectin provides a smooth texture to the sorbet.
Low-oil or no-oil salad dressings use iota or kappa to help suspend herbs, etc., and to provide the mouth feel that is expected from a normal salad dressing. The low oil content of reduced-oil mayonnaise normally gives a thin product, rather like a hand lotion; additives are needed to thicken it and to stabilize the oil-in-water emulsion. A combination of carrageenan and xanthan gum is effective. Xanthan gum is made by a bacterial fermentation process; its development was pioneered in the early 1960s by the Kelco Company, then the largest producer of alginate; it is now an accepted and widely used food additive. The interaction of carrageenan and protein can be used in the clarification of beer, with the complex formed precipitating from the wort. More water-based applications of carrageenan are given in the references below.

7.3.3 Meat products

In preparing hams, addition of carrageenan to the brine solution used in pumping improves the product because the carrageenan binds free water and interacts with the protein so that the soluble protein is retained. For successful penetration, the brine solution must have a low viscosity, but dissolved carrageenan would increase the viscosity. The carrageenan is therefore dispersed in the water after the brine salts are added; the carrageenan does not dissolve because of the high salt concentration, but as the ham cooks it does dissolve and is then effective.
There is a growing consumer demand for pre-cooked poultry products such as chicken and turkey pieces. Poultry processors were concerned about the loss of water during cooking (this lowered their yield per unit weight of product) and the loss in texture and eating quality that resulted. By injecting a brine containing salt, phosphate and carrageenan into the muscle of the meat, these problems are overcome. As the meat cooks, the carrageenan binds water within the poultry muscle and improves texture and tenderness. The processors are pleased because they now have a higher yield; in fact they find that he can even add some extra water to the poultry and it will be retained. The consumer receives a better product. The carrageenan producer is pleased because about 0.5 percent carrageenan is added, much more than the 0.05-0.1 percent used in dairy products. The future looks bright for this kind of application in meat products.
Hydrocolloids are being tried as fat replacements in low-fat products, with varying degrees of success. When fat or salt are reduced, meat and poultry can suffer loss of tenderness, juiciness and flavour. Low-fat products formulated with phosphates and carrageenan can have the juiciness and tenderness restored. Kappa carrageenan has been used with some success in replacing half the normal fat in frankfurters. Reduction of fat in ground meat products like hamburgers results in a different mouth feel and dry taste, which consumers do not always accept. Iota can be mixed with fresh ground beef and when cooked it provides fat-like characteristics and moisture retention that make the product more acceptable. This was the basis for McDonald's "MacLean" hamburger.

7.3.4 Pet food

This is the largest application for SRC, known as seaweed flour (see Section 7.1.2), using about 5 500 tonnes annually. Refined carrageenan could also be used, but its cost is too high and seaweed flour is about one-quarter of its price. Seaweed flour becomes an even better proposition because when combined with locust bean gum, less carrageenan is required, but this combination still gives an excellent product and it is very affordable. The meat used in canned pet foods is usually waste cuts from the abattoir. It is chopped into chunks or smaller pieces, mixed with water, flavours, seaweed flour (kappa carrageenan) and locust bean gum, canned and cooked. The two hydrocolloids help to bind the meat together and, depending on the concentrations used, either provide a thickened gravy around the meat pieces or a flavoured jelly, either of which enhances the appearance of the product as it is removed from the can. Konjac (or konjaku) gum, made from the konjac tuber or elephant yam (Amorphophallus konjac), can be used in place of locust bean gum. Konjac gels are clearer than locust bean gels and can help with costs when the price of locust bean gum rises, as it does occasionally.

7.3.5 Air freshener gels

When you need to improve the odours in your room, air freshener gels are one of the products available at supermarkets. They are made from kappa carrageenan, a potassium salt, water and perfume. When mixed, the perfumed gel forms and it is moulded to a shape to fit the holder. When purchased, the holder is sealed; to use, the holder is opened slightly and the moisture plus perfume are gradually released from the gel. Eventually the gel dries out leaving a small residue in the holder, which is then discarded. About 200 tonne/year of seaweed flour grade of carrageenan is the estimated consumption for this application.

7.3.6 Toothpaste

The essential ingredients in toothpaste are chalk or a similar mild abrasive, detergent, flavour, water and a thickening agent that will provide enough body to the paste to ensure that the abrasive is kept in suspension and that there is no separation of water. A thixotropic thickener is preferable, i.e. that has gel-like properties when allowed to stand but that will flow when pressure is applied to it. Iota carrageenan, at about 1 percent, is one of the most useful thickening agents, it meets the above criteria and gives a paste that is easily rinsed from the toothbrush. When the size of the toothpaste market is considered, even at 1 percent concentration this represents a large market for iota.

7.3.7 Immobilized biocatalysts

This application was discussed for alginates in Section 5.3.3. Carrageenan gels are another medium for immobilizing enzymes or whole cells. Kappa carrageenan gives the strongest gels and beads made from this show sufficient mechanical strength for packing in columns, and yet they are permeable to most substances.

7.3.8 For further details

More information about the properties and applications of carrageenans can be found in the following references, the first two of which are probably the most useful: Stanley (1990), Therkelsen (1993), Nussinovitch (1997), Stanley (1987).
For quick reference to a list of uses and the concentrations of carrageenan required, see Tables 3.4 and 3.5 in Thomas (1997).

7.3.9 Refined grade vs natural grade

Natural grade carrageenan is cheaper to make and requires a smaller capital outlay, therefore its price is lower than the refined or filtered grade. Natural grade is now approved for human use in most applications and jurisdictions. For a very useful and interesting discussion of the pros and cons of refined versus natural grades in regard to their purity, composition, and comparative performance in various applications, see Bixler (1996).

7.4 Markets and marketing of carrageenan

A summary of carrageenan markets is shown in Table 9. The total market has a value of about US$ 300 million. The marketing of carrageenan poses similar problems to those previously described in Section 5.4 for alginate. The original companies invested heavily in processing equipment and provided strong research and development facilities to assist customers and promote sales. These companies are now part of large multinationals and have a strong commitment to selling the refined carrageenan that they have always produced, and they operate at about 80-85 percent capacity. With the introduction of the simpler processing required for seaweed flour, many small companies entered that market, which required very little R&D because sales were mainly to pet food producers who knew exactly what they wanted and how to use it. Some of these companies then expanded their operations to produce the PES/PNG grade for human consumption. They make a few basic kappa and iota carrageenans for use in meat products, and to a lesser degree in dairy products. However, they lack the technical marketing skills to sell their products against the larger multinationals. These smaller companies are mainly in the Philippines and Indonesia, and operate at probably about 50 percent capacity and some are possibly struggling to survive. Despite this, new production facilities continue to be built in China and eastern Africa.
While there are difficulties in production of carrageenan, marketing can be even more difficult without adequate technical expertise to assist customers in the use of the product. Producers of refined carrageenan are not especially interested in selling the less expensive PES grade if such sales are going to replace sales of their refined grade. So there are opportunities for PES producers to penetrate the human food market with their less expensive product, if they are willing to invest in the technical expertise needed to service those sales. This has already occurred in the United States of America, where about 20 percent of the market is now PES grade. There appear to be similar opportunities awaiting PES producers in European markets that are still predominantly users of the refined grade (H.R. "Pete" Bixler, 2002, pers. comm.).
TABLE 9
Carrageenan markets (2001)

Application	tonnes	%
Dairy	11 000	33
Meat and poultry	5 000	15
Water gels	5 000	15
PES food grade	8 000	25
Toothpaste	2 000	6
Other	2 000	6
Total	33 000	100

Source: H. Porse, CP Kelco ApS, 2002, pers. comm.

7.5 Future prospects

In developed markets, such as the United States of America, Europe and Japan, all known applications are almost fully exploited. There could be some expansion by replacement of some of the gelatin market because of health concerns about bovine spongiform encephalopathy, but also due to a growing vegetarian population. Elderly people tend to use more processed foods in their diets and as this population increases so too will carrageenan consumption. Taking these factors into account, a 2-4 percent growth per annum can be expected in developed countries, and there the market splits about 50:50 between dairy and meat applications.
In areas such as Central and South America, Eastern Europe and Southeast Asia, growth will be stronger. Here the per capita consumption of carrageenan should increase by 50 percent over the next five years, due to market penetration alone. Allowing for population growth and assuming a moderate economic growth, an expansion of carrageenan consumption by 5-7 percent per annum is likely. At present the market is split into approximately 20 percent dairy and 80 percent meat applications, but this is likely to change with a gradual increase in the dairy foods market (H.R. "Pete" Bixler, 2002, pers. comm.).
For further details, see Bixler (1996), who discusses recent developments in the manufacturing and marketing of carrageenan and is excellent reading for anyone interested in obtaining an overall view of the carrageenan industry.

SEAWEEDS USED AS A SOURCE OF CARRAGEENAN

6.1 Genera and species used

Most carrageenan is extracted from Kappaphycus alvarezii and Eucheuma denticulatum. The original source of carrageenan was Chondrus crispus, and this is still used to a limited extent. Betaphycus gelatinum is used for a particular type of carrageenan. Some South American species that have previously been used to a limited extent are now gaining favour with carrageenan producers as they look for more diversification in the species available to them and the types of carrageenan that can be extracted. Gigartina skottsbergii, Sarcothalia crispata and Mazzaella laminaroides are currently the most valuable species, all collected from natural resources in Chile. Small quantities of Gigartina canaliculata are harvested in Mexico. Hypnea musciformis has been used in Brazil.
Over the last few years most of these seaweeds have been reclassified by marine biologists as they gain more knowledge of their structure. If readers are to go beyond this publication for further information, they need to be familiar with the both the old and new names, as listed below.

• Betaphycus gelatinum was Eucheuma gelatinae.
  
• Chondrus crispus remains unchanged, and is commonly known as "Irish Moss."
  
• Eucheuma cottonii is now Kappaphycus alvarezii, and commercially was and is called "cottonii".
  
• Eucheuma denticulatum was Eucheuma spinosum and commercially was and is called "spinosum".
  
• Eucheuma gelatinae is now Betaphycus gelatinum.
  
• Eucheuma spinosum is now Eucheuma denticulatum and commercially was and is called "spinosum".
  
• Gigartina canaliculata remains unchanged.
  
• Gigartina skottsbergii remains unchanged.
  
• Gigartina stellata, mentioned in earlier articles but now not so important, is now Mastocarpus stellatus.
  
• Hypnea musciformis remains unchanged.
  
• Iridaea ciliata is now Sarcothalia crispata.
  
• Iridaea laminaroides is now Mazzaella laminaroides.
  
• Kappaphycus alvarezii was Eucheuma cottonii and commercially was and is called "cottonii".
  
• Mazzaella laminaroides was Iridaea laminaroides.
  
• Mastocarpus stellatus was Gigartina stellata, mentioned in earlier articles but now not so important.
  
• Sarcothalia crispata was Iridaea ciliata.

6.2 Natural habitats

The definitions of the vertical zones of the shore, littoral fringe, eulittoral and sublittoral were given in Section 2.2.
Kappaphycus alvarezii (Figures 33 and 34) is found in the upper part of the sublittoral zone, from just below the low tide line, of reef areas on sandy-corally to rocky substrates where water flow is slow to moderate.
Eucheuma denticulatum thrives on sandy-corally to rocky substrates in areas constantly exposed to moderate to strong water currents.
Betaphycus gelatinum (Figure 35) grows on rocky, coralline substrates, a few metres from the reef-edge, where it is exposed to strong wave action and turbulence.

FIGURE 33
Fresh Kappaphycus alvarezii.

FIGURE 34
Dried Kappaphycus alvarezii.

FIGURE 35
Betaphycus gelatinum drying (Hainan Island, China).

All three require water temperatures of 21°C or more and they thrive in bright light.
Chondrus crispus (Figure 36) grows from the littoral fringe to 20 m below mean low water, depending on the wave motion, transparency and rocky structures available. Usually it is most abundant from mean low water to the mid-sublittoral zone. It grows best on stable rock ledges and large boulders, preferring horizontal shelves, growing not so well on smaller rocks or sediment-covered rocks. Strongest growth is in late spring and summer; least growth is in winter.
Gigartina skottsbergii (Figure 37) grows in the sublittoral at depths of 9-15 m. It grows best in the summer.
Sarcothalia crispata is found from the eulittoral to the sublittoral, down to a depth of 10 m.
Mazzaella laminaroides grows in the eulittoral zone on wave-exposed sites, also in estuaries. Where people collect intertidal gastropods (potential algal grazers), the growth of Mazzaella laminaroides flourishes.
Gigartina canaliculata and Hypnea musciformis grow in the eulittoral zone.

FIGURE 36
Chondrus crispus. (after Hansen, Packard and Doyle, 1981).

FIGURE 37
Gigartina skottsbergii

M. AVILA, INSTITUTO DE FOMENTO PESQUERO, PUERTO MONTT, CHILE

6.3 Sources of carrageenophytes

Kappaphycus alvarezii and Eucheuma denticulatum were originally harvested from natural stocks growing in Indonesia and the Philippines. In the 1970s, cultivation began in both countries and this now supplies most of these species, with only small quantities being collected from the wild. Cultivation has spread to other countries, most successfully in Tanzania (Zanzibar), Viet Nam and some of the Pacific Islands, such as those of Kiribati. Wild Betaphycus gelatinum is harvested mainly in Hainan Island, China, Taiwan Province of China and the Philippines, and it is cultivated on Hainan Island.
Chondrus crispus is harvested for carrageenan production in Canada (Nova Scotia and Prince Edward Island), United States of America (Maine and Massachusetts) and France.
Gigartina skottsbergii, Sarcothalia crispata and Mazzaella laminaroides are all harvested from natural resources in Chile, mainly central Chile from Valparaiso to Chiloe Island.
Some Gigartina skottsbergii is also harvested in Argentina.
Gigartina canaliculata is harvested in Mexico (Baja California), and is available from south of Ensenada to Punta San Antonio. Hypnea musciformis occurs along most of the coastline of Brazil, but production is erratic in both space and time, increasing the costs of harvesting.
The industry needs about 13 percent of the dry seaweed used annually for production of carrageenan as temperate-water Gigartina-like species. These contain lambda carrageenan and a "weak" kappa; the properties of the latter lie between those of a normal kappa (such as obtained from Kappaphycus alvarezii) and iota carrageenan. While 1 000-2 000 tonnes come from older sources, such as France and Canada, over 90 percent today comes from Chile. None of the carrageenophytes from Chile is currently cultivated, all come from natural regrowth. Nevertheless there seems to be no evidence of overharvesting and there are areas for expanding the harvest of the most important species, Gigartina skottsbergii. This seaweed grows from Puerto Montt to Puenta Avenas. While fishermen are not currently available to harvest along this coastline, an increase in demand would probably stimulate the population shift needed to meet the increase (H.R. "Pete" Bixler, 2002, pers. comm.).

6.4 Harvesting methods for wild carrageenophytes

Chondrus crispus has been harvested in Canada since the 1920s, but only came to prominence during the Second World War, when access to Japanese agar stopped and the Irish Moss beds in France also became inaccessible. Production on Prince Edward Island jumped from 5 dry tonnes in 1940 to 900 dry tonnes in 1942. The original collection was from storm tossed seaweed, driven onto the shore by strong winds. Local farmers picked it up from beaches and shores and sometimes waded into the surf with horse-drawn scoops to capture unattached moss. Fishermen took their boats offshore with hand rakes and scrapped the moss from the flat rock shelf where it grew. In the 1970s, large lobster boats equipped with drag rakes and winches were introduced; the steel rakes - about 1 m wide, 25 kg, with about 40 teeth - are dragged across the moss beds. The scale of operation of these boats had a rather severe effect on the regrowth of the beds and perhaps it was fortunate that demand for moss declined sharply as the cultivated Kappaphycus and Eucheuma became available from the Philippines in the 1980s. With a low demand from carrageenan processors, Irish Moss harvesting has returned to being a part-time fishery, where there is a place for operators equipped with small boats, outboard motors and hand rakes.
For further details of Chondrus crispus harvesting in Canada, with very good illustrations of equipment and operations, see Pringle and Mathieson (1986).
Chondrus crispus in France grows mainly around Brittany. However, there are no flat beds, as found in Canada, so the use of dredgers is not possible, only manual gathering. Harvesting is a part-time operation by about 3 000 people, although this number and the harvest are both falling as the living standards of the harvesters rise.
Betaphycus gelatinum on Hainan Island, China, is most abundant about 1 m below the low tide mark and was collected by hand, but cultivation has overtaken this practice.
Gigartina canaliculata grows in the eulittoral zone in Mexico and is harvested from May to September by fishermen, who pull it by hand during low tide.
Mazzaella laminaroides is harvested from the eulittoral zone by people walking around the rocks at low tide and pulling the seaweed from the rocks by hand.
Sarcothalia crispata is harvested from the sublittoral zone by fishermen who dive and use hooks to drag the seaweed off the rock and store it in bags called chinguillos while they work.
Gigartina skottsbergii is harvested from the lower sublittoral zone in the same way as Sarcothalia crispata. Depending on the area where they dive, each fisherman is able to harvest about 70 kg/hour from a natural bed.

6.5 Cultivation of carrageenophytes

Kappaphycus and Eucheuma are both cultivated by the same methods, the two most popular being the fixed, off-bottom line method and the floating raft method.
The basics of the fixed, off-bottom line method are simple. First choose a suitable site, then drive two wooden stakes, about 5-10 m apart, into the bottom. Stretch either a monofilament nylon line or a polypropylene rope between the stakes; the line should be 20-30 cm above the sea bottom and the water must be deep enough to ensure that the seaweed is not exposed at low tide. Small pieces of seaweed (50-100 g) are tied to the line. Many of these lines are constructed, usually 1 m apart (Figure 38). If the site is suitable and farming maintenance is carried out regularly, the seaweed should reach 10 times its original size in 6-8 weeks, when it can be harvested. It is sun dried away from sand and dirt, then packed into bales ready for shipping.
The main factor determining success or failure is choosing a suitable site. If Kappaphycus or Eucheuma is growing naturally, the place is probably suitable. If not, the following criteria apply.

• Reefs, well away from any freshwater sources (small rivers, etc.), have proven to be good sites. If the seawater salinity (usually 35 parts of salt per 1 000 parts of water (parts per thousand = ppt)) falls below 30 ppt, the seaweed does not grow well.
  
• Water temperature should be 25-30°C; in shallow water near the beach, the water temperature may become too high during the day; a good site is between the low tide limit and the reef edge.
  
• The seaweed obtains its nutrients for growth from the water so water movement through the seaweed is important. Moderate water movement is preferable; this also helps to stabilize water temperature and salinity. If the current is too strong it can cause pieces of the growing plant to break off and be lost; wave action must be avoided for the same reason.
  
• The sea bottom type is important; a white, firm bottom with a limited amount of natural seaweed is good, too much seaweed or sea grass will compete for nutrients with the cultivated seaweed. Silt or mud on the bottom indicates possible poor water flow and if the silt is disturbed it may settle on the plants; muddy water will also reduce the light available to the seaweed.
  
• Plenty of sunlight is necessary for good growth; seaweed planted in shallow water (30-50 cm) grows well; in deeper water (more than 1 m) the light is reduced and growth is poor. Water depth is also important for farming: 0.5-1.0 m depth at low tide is good for the seaweed and allows the farmer to carry out maintenance more easily.
  
• Regular maintenance is essential. It consists of removing other seaweeds growing either on the lines or the crop itself, removing poorly growing plants, replacing lost plants, and making any necessary repairs to the stakes and lines.

FIGURE 38
Kappaphycus alvarezii cultivation using fixed, off-bottom lines (Kiuva, Fiji).

Once a site has been chosen, a trial is made using the chosen species. A few lines are set out at each of several different parts of the site, small pieces of the seaweed are attached and their growth rate is monitored weekly. If after 2-3 months the daily growth rate is 3-5 percent, the site is probably suitable and a small farm can be established. Because of the larger capital outlay required for large installations, before venturing into large farms it is advisable to monitor conditions for a full year so that the effects of all weather and other ecological factors are known. Small family farms have been the most successful, partly because there is more incentive to provide the necessary care and maintenance to the farm they own rather than one owned by an employer.
Various problems can arise. Grazing fish can damage the crop. Siganids (rabbitfish) and puffers are common pests. Siganids are the most destructive, especially if the plants are all small: the entire crop can be devoured and even dense beds can be severely damaged. There is no simple solution except to move to another site where they are not prevalent. Turtles pose a special problem: they obviously take large bites but they also crawl through a farm, causing devastating physical damage. Long-spined sea urchins are also a pest, and can cause injury to the farmer as they try to remove them. The most common symptom of bad health is ice-ice, so named because of the white segments that appear on the plants, causing them to break at that point. There is some disagreement about its cause: some say it is a symptom of a bacterial or viral infection, others attribute it to physical stress caused by changes in the environment in which it is growing. Storms lead to strong water movement that can cause plants to break apart and even cause physical damage to the lines and stakes. So localities that are subject to seasonal cyclones, etc., should be avoided, or precautions taken during the periods - usually about 3 months of the year - when bad weather can be expected.
The materials required include the wooden stakes used to hold the lines, which can be made from mangrove timbers or any other timber that can withstand immersion in seawater for at least a year; they need to be 5-10 cm diameter, sharpened at one end (Figure 39) and driven into the bottom until held very firmly. Monofilament nylon line with a breaking strain of 90 kg (200 lb) is used to support the seaweed, or 3 mm diameter polypropylene rope. The rope has an advantage in that the string used to tie the seaweed to the line can actually be inserted through the twist of the rope, ensuring it does not slide along the rope. The seaweed is tied to the line with a soft synthetic string, often called a "tie-tie", preferably using a slip knot so that the seaweed can be easily removed at harvest time. The seedlings, 50-150 g pieces obtained from the last harvest or the nearest farm, are prepared by fixing the tie-ties to them (Figure 40), ensuring that they are kept moist all the time that they are not in the water. Seedlings and tie-ties are then fixed to the ropes at 20-25 cm intervals (Figure 38), the ropes can already be in the water attached to the stakes or it can be done on the land and the ropes then stretched between the stakes. At harvest time, the whole plant is removed and new seedlings are cut from the tips.

FIGURE 39
Stakes from mangrove trees for use with fixed, off-bottom lines.

FIGURE 40
Fixing "tie-ties" to seedlings, using 20-25 cm pieces of blue plastic raffia.

To maintain the value of the crop, careful post-harvest treatment is necessary. It must be kept away from sand and dirt, so drying racks or mats are used (Figure 41). In some areas, the entire line is removed from the sea and hung over a tall "fence" to allow drying, the seaweed being untied after it has dried. In most areas, sun drying for about 2-3 days is sufficient to reduce the moisture content to the required 35 percent level. With practice, farmers can estimate the moisture level by feeling the seaweed, by its firmness and how it bends. If the moisture is above 40 percent the seaweed may rot during storage and transport; below 35 percent the seaweed becomes too firm and bouncy and it is difficult to compress it into bales. During drying, white salt-like crystals appear on the outside of the seaweed; any that are loose and can be shaken off are removed. Buyers do not like damp seaweed, nor foreign matter such as sand, dirt, stones, coral pieces or excessive salt. Some less scrupulous farmers have been known to add salt to the dried product since they are paid by weight and salt is cheaper than seaweed.

FIGURE 41
Drying Kappaphycus alvarezii.

The second method of cultivation is the floating raft method. This is suitable in protected areas where water current is weak or where the water is too deep for fixed bottom lines. The selected areas must meet the criteria previously described, at least as they apply to this situation, and trials should be conducted in the same way. A white, silt-free bottom is not necessary. A floating construction is used to suspend the seaweed about 50 cm below the surface. Often a 3×3 m square timber frame, made from bamboo or mangrove timber, is used with 3 mm polypropylene ropes stretched parallel in one direction between the timbers, at 10-15 cm intervals (Figure 42). The seedlings are tied to the ropes and the raft is anchored to the bottom. The anchor ropes may need to hold the raft below the surface at the beginning, but as the plants grow and add weight to the raft, it may need extra support (such as polystyrene foam boxes tied to the corners of the raft) to prevent it sinking too low in the water. The seedlings can be tied to the raft on land and the raft towed into position. Regular maintenance during growth is still required. At harvest time the entire raft can be removed and used as a drying rack by suspending it between four corner supports, such as large drums.

FIGURE 42
A raft for use in the floating-raft method of cultivation.

The off-bottom line farming method allows easier access since the farmer can walk around the lines at low tide, but the floating rafts have the advantage that they can be easily moved to another position if necessary, and removed from the water altogether in bad weather, thus avoiding destruction by heavy seas and strong winds.
For further details
Methods and illustrations can be found in Trono (1993) and its associated CD-ROM, Critchley and Ohno (1997). For a thorough discussion of cultivation and some of its associated problems see Doty (1986), who also examines some of the costs and returns from farming.
Very practical guides to Eucheuma and Kappaphycus cultivation, with useful illustrations, can be found in Foscarini and Prakash (1990) or Ask (1999).
Foscarini and Prakash (1990) is written for the person actually setting up a farm, written simply but carefully, and answers questions such as:

• How much will it cost to start seaweed farming?
• How can I organize my work at the farm?
• What should I do to maintain my farm?
• What records do I need to keep?
• How much will I earn from my seaweed farm?

Copies are available upon request from the FAO David Lubin Library (see reference for details).
Ask (1999) is similar, and copies may be available from the author (see references).
Similar guides may be available from other carrageenan producers, listed in Section 7.2.
In Viet Nam, Kappaphycus is being cultivated in offshore areas using floating rafts, in lagoons and inlets using fixed off-bottom monolines, and it is the only country to date that has also used ponds for Kappaphycus. Fixed off-bottom monolines and fixed off-bottom nets have been used in ponds with muddy bottoms, while broadcasting seedlings directly onto the bottom is used where the bottom is sandy or coralline. Sometimes the ponds are used for seaweed for six months and then rotated with shrimp for six months.
Betaphycus gelatinum is cultivated on Hainan Island, China. Pieces of wild seaweed are fastened to coral branches with rubber rings and thrown onto sublittoral reefs, where divers rearrange them. Some long-line cultivation has also been used.
In France, one company cultivated Chondrus crispus in raceways and found it an economic proposition from 1978 to 1996. Its success was related to the selection of a fast-growing strain and an automated system that together produced a growth rate ten times faster than the natural rate. However, by 1996, the cost of wild C. crispus had fallen and the operation was no longer considered economic.
Methods for the cultivation and restocking of Gigartina skottsbergii have resulted from collaboration between the Division of Aquaculture, Instituto de Fomento Pesquero, and the Department of Oceanography, Universidad de Concepción, Chile, and have been published as Romo, Ávila and Candia (2001).
Cultivation methods for Sarcothalia crispata are being developed.

6.6 Quantities harvested

About 120 000 dry tonne/year is harvested of Kappaphycus alvarezii, mainly from the Philippines, Indonesia and Tanzania (Zanzibar). For Eucheuma denticulatum, the harvest is around 30 000 dry tonne/year, again mainly from the same countries. About 300 dry tonne/year of Betaphycus gelatinum is harvested yearly from Hainan Island, mainly from cultivation.
Until the early 1970s, Chondrus crispus was the main source of carrageenan and Canada provided about 70 percent of the world production. By 1992, with the success of cultivation of K. alvarezii and E. denticulatum, the demand for C. crispus had fallen to 3.8 percent of the total requirement for carrageenophytes, and of this, Canada supplied only 12 percent. In 1992, only about 7 000 wet tonnes was harvested, compared with the peak production of 50 000 wet tonnes in 1974. In France, there has also been a decline in harvesting, from about 6 000 wet tonnes in 1975 to about 3 000 wet tonnes in 1996.
The Gigartina skottsbergii harvest in Chile was 30 100 wet tonnes in 2000. The Gigartina canaliculata in Mexico has fallen from a maximum production of 1 100 dry tonnes in 1978 to 200 dry tonnes, and it is all exported. Small quantities of other species are collected from Mexico, Morocco and Peru.
Table 7 summarizes estimates of harvests of carrageenophytes, all in dry tonness.
TABLE 7
Carrageenophyte resources, tonnes dry weight (2001)

Chondrus
Canada	2 000
France, Spain and Portugal	1 400
Republic of Korea	500
Subtotal	3 900	2.3%
Eucheuma and Kappaphycus
Indonesia	25 000
Philippines	115 000
Tanzania (Zanzibar)	8 000
Others	1 000
Subtotal	149 000	88.5%
Gigartina
Chile	14 000
Morocco, Mexico and Peru	1 500
Subtotal	15 500	9.2%
Total	168 400	100%

Source: H. Porse, CP Kelco ApS, 2002, pers. comm.

FIGURE 43
Marketing channel for seaweed - Indonesia (Burges Watson, 1999).

6.7 Markets

For Kappaphycus and Eucheuma, the farmers usually sell to middlemen; sometimes there may be two in the chain. They sort and clean up the seaweed before selling it on to the carrageenan processors. The middlemen frequently help to finance the farmers with loans for equipment and seedlings. As cultivation in the Philippines has developed, some of the major processors have set up extraction factories there, eliminating the former transport costs to Europe. Two distinct grades of carrageenan are produced: refined and semi-refined. Large quantities of seaweed produced in the Philippines are now processed there, producing all grades of carrageenan.
In Indonesia, again, there are active middlemen and a few local companies making semi-refined carrageenan (SRC). Figure 43 shows the marketing chain for Kappaphycus in Indonesia, and this is also typical of the situation in other countries, such as the Philippines. A large proportion of the seaweed is exported to Japan and the Republic of Korea. In Zanzibar (Tanzania) all the production is exported, mainly to the companies who helped to establish the industry. Pacific nations such as Kiribati have a transport cost problem but have entered into contracts with at least one major producer who is willing to pay a fixed price if the supply is assured. The farmgate price of these seaweeds has undergone severe fluctuations in the past, with boom and bust cycles that are harmful to both buyer and seller in the long term. Fixed price contracts assure the farmers of a steady income, otherwise when the farm gate price falls too low they simply abandon seaweed farming and return to fishing and other activities that sustain a subsistence living. This eventually leads to a shortage, a demand that cannot be met, giving rise to increased prices. In Chile there is large internal consumption by four processors; the remainder is exported through several intermediary companies. A useful review of trends of seaweed production in Chile includes a diagram showing the marketing channels within Chile (Norambuena, 1996). All the Betaphycus gelatinum produced in China is used there. In France, all Chondrus harvested is used locally. Canadians operate fishermens' cooperatives that sell Chondrus to FMC Biopolymer, based in nearby Maine, and also export to Europe.

6.8 Future prospects

Demand for carrageenan has risen at a steady rate of about 5 percent annually, and this should continue for several years as a continuing increase in demand is forecast. Carrageenan extractors actively pursue a policy of assistance to those interested in establishing seaweed farms, so future prospects for the industry are very encouraging.

ALGINATE

5.1 Alginate production methods

5.1.1 Sodium alginate

"Alginate" is the term usually used for the salts of alginic acid, but it can also refer to all the derivatives of alginic acid and alginic acid itself; in some publications the term "algin" is used instead of alginate. Alginate is present in the cell walls of brown algae as the calcium, magnesium and sodium salts of alginic acid. The goal of the extraction process is to obtain dry, powdered, sodium alginate. The calcium and magnesium salts do not dissolve in water; the sodium salt does. The rationale behind the extraction of alginate from the seaweed is to convert all the alginate salts to the sodium salt, dissolve this in water, and remove the seaweed residue by filtration. The alginate must then be recovered from the aqueous solution. The solution is very dilute and evaporation of the water is not economic. There are two different ways of recovering the alginate.
The first is to add acid, which causes alginic acid to form; this does not dissolve in water and the solid alginic acid is separated from the water. The alginic acid separates as a soft gel and some of the water must be removed from this. After this has been done, alcohol is added to the alginic acid, followed by sodium carbonate which converts the alginic acid into sodium alginate. The sodium alginate does not dissolve in the mixture of alcohol and water, so it can be separated from the mixture, dried and milled to an appropriate particle size that depends on its particular application.
The second way of recovering the sodium alginate from the initial extraction solution is to add a calcium salt. This causes calcium alginate to form with a fibrous texture; it does not dissolve in water and can be separated from it. The separated calcium alginate is suspended in water and acid is added to convert it into alginic acid. This fibrous alginic acid is easily separated, placed in a planetary type mixer with alcohol, and sodium carbonate is gradually added to the paste until all the alginic acid is converted to sodium alginate. The paste of sodium alginate is sometimes extruded into pellets that are then dried and milled.
These essentials of the process are illustrated in the flow diagram in Figure 32.
The process appears to be straightforward, certainly the chemistry is simple: convert the insoluble alginate salts in the seaweed into soluble sodium alginate; precipitate either alginic acid or calcium alginate from the extract solution of sodium alginate; convert either of these back to sodium alginate, this time in a mixture of alcohol and water, in which the sodium salt does not dissolve.
The difficulties lie in handling the materials encountered in the process, and to understand these problems a little more detail of the process is required.
To extract the alginate, the seaweed is broken into pieces and stirred with a hot solution of an alkali, usually sodium carbonate. Over a period of about two hours, the alginate dissolves as sodium alginate to give a very thick slurry. This slurry also contains the part of the seaweed that does not dissolve, mainly cellulose. This insoluble residue must be removed from the solution. The solution is too thick (viscous) to be filtered and must be diluted with a very large quantity of water. After dilution, the solution is forced through a filter cloth in a filter press. However, the pieces of undissolved residue are very fine and can quickly clog the filter cloth. Therefore, before filtration is started, a filter aid, such as diatomaceous earth, must be added; this holds most of the fine particles away from the surface of the filter cloth and facilitates filtration. However, filter aid is expensive and can make a significant contribution to costs. To reduce the quantity of filter aid needed, some processors force air into the extract as it is being diluted with water (the extract and diluting water are mixed in an in-line mixer into which air is forced). Fine air bubbles attach themselves to the particles of residue. The diluted extract is left standing for several hours while the air rises to the top, taking the residue particles with it. This frothy mix of air and residue is removed from the top and the solution is withdrawn from the bottom and pumped to the filter.
The next step is precipitation of the alginate from the filtered solution, either as alginic acid or calcium alginate.

FIGURE 32
Flow chart for the production of sodium alginate (after McHugh, 1987).

Alginic acid method
When acid is added to the filtered extract, alginic acid forms in soft, gelatinous pieces that must be separated from the water. Again flotation is often used; filtration is not possible because of the soft jelly-like nature of the solid. If an excess of sodium carbonate is used in the original extraction, this will still be present in the filtered extract so that when acid is added, carbon dioxide will form. Fine bubbles of this gas attach themselves to the pieces of alginic acid and lift them to the surface where they can be continuously scrapped away. The processor now has a jelly-like mass of alginic acid that actually contains only 1-2 percent alginic acid, with 98-99 percent water. Somehow, this water content must be reduced. It is too soft to allow the use of a screw press. Some processors place the gel in basket-type centrifuges lined with filter cloth. Centrifuging can increase the solids to 7-8 percent and this is sufficient if alcohol is to be used in the next step of converting it to sodium alginate. It is also now sufficiently firm to be squeezed in a screw press. The 7-8 percent alginic acid is place in a mixer and, allowing for the water contained in the alginic acid, enough alcohol (usually ethanol or isopropanol) is added to give a 50:50 mixture of alcohol and water. Then solid sodium carbonate is added gradually until the resulting paste reaches the desired pH. The paste of sodium alginate can be extruded as pellets, oven dried and milled.
Calcium alginate method
When a soluble calcium salt, such as calcium chloride, is added to the filtered extract, solid calcium alginate is formed. If the calcium solution and filtered extract are mixed carefully, the calcium alginate can be formed as fibres - bad mixing gives a gelatinous solid. This fibrous material can be readily separated on a metal screen (sieve) and washed with water to remove excess calcium. It is then stirred in dilute acid and converted to alginic acid, which retains the fibrous characteristics of the calcium alginate. This form of alginic acid can be easily squeezed in a screw press. A screw press with a graduated-pitch screw is usually used; the squeezing action must be applied very gradually, otherwise the material will just move backwards and out of the press. The product from the screw press looks relatively solid but still contains only 20-25 percent alginic acid. However, it is dry enough to form a paste when sodium carbonate is mixed with it to convert it to sodium alginate. Sodium carbonate is added to the alginic acid in a suitable type of mixer until the required pH is reached, then the paste is extruded as pellets, dried and milled.
The disadvantage of this second method, compared to the alginic acid method, is that an extra step is added to the process. The advantage is that the handling of the fibrous calcium alginate and alginic acid is much simpler and alcohol is not needed. Alcohol is expensive and while it is usually recovered and recycled, recovery is never 100 percent, so its use adds to the costs.
Other important factors in alginate production are colour control of the product, water supply and waste disposal.
If the original seaweed is highly coloured, e.g. Ascophyllum, the alkaline extract will also be highly coloured and the process will eventually yield a dark product that commands only a low price as it is limited to use in technical applications. Lighter coloured seaweeds, such as Macrocystis, yield a lighter coloured alginate suitable for food and other applications. Colour can be controlled by the use of bleach - sodium hypochlorite - that is added to the filtered alkaline extract or even to the paste at the final conversion stage. Care must be taken, since excessive bleach can lower the viscosity of the alginate, reducing its value. Sometimes the seaweed is soaked in a formalin solution before it is extracted with alkali. The formalin helps to bind the coloured compounds to the cellulose in the cell walls, so much of the colour is left behind in the seaweed residue when the alkaline extract is filtered.
Large quantities of water are used in the process, especially when diluting the thick (viscous) initial alkaline extract to a viscosity suitable for filtration. A plentiful and reliable water supply is a necessity for an alginate factory to survive.
Waste waters from filtration are alkaline, they contain calcium from the calcium precipitation (excess calcium gives a more fibrous calcium alginate) and acid from the acid conversion step. In some countries the waste is pumped out to sea. Where environmental concerns are greater, or when water supplies are limited, recycling is not too difficult and its costs may be partly offset by the lowering of the quantity and cost of water used by the factory. A means of disposing of solid wastes - the seaweed residue and used filter aid - must be found. There have been several positive studies reported on the use of this waste to adsorb heavy metals, such as cadmium, zinc and copper, from industrial liquid wastes (e.g. Romero-Gonzalez, Williams and Gardiner, 2001). Attempts to ferment this waste to produce ethanol from the cellulose content appear to be less promising, in economic terms (Horn, Aasen and Oestgaard, 2000).
For further details
In the above descriptions of the production process, suggestions about the detail of reagent concentrations, time, temperatures, etc., have been deliberately omitted to simplify the reading of it. Commercial processors regard these details as confidential and do not publish them. However, some detail can be found in McHugh (1987) and in the results of a series of trials, run on a pilot-plant scale using Macrocystis as raw material, published by Hernández-Carmona et al. (1998), Hernández-Carmona, McHugh and López-Gutiérrez (1999), McHugh et al. (2001) and Hernández-Carmona et al. (2002).

5.1.2 Other alginate products

Sodium alginate, produced as described above, is the main form of alginate in use. Smaller quantities of alginic acid and the calcium, ammonium and potassium salts, and an ester, propylene glycol alginate, are also produced. Calcium alginate and alginic acid are made during the calcium alginate process for making sodium alginate; each can be removed at the appropriate stage and, after thorough washing, can be dried and milled to a required particle size. The other salts are made by neutralization of moist alginic acid with the appropriate alkali, usually ammonium hydroxide or potassium carbonate; sufficient water or alcohol can be added to keep the material at a workable consistency; they are processed as described for the paste-conversion method in the calcium alginate process for sodium alginate production.
Propylene glycol alginate, an ester of alginic acid, has different properties and uses from the salts such as sodium alginate. It was first patented in 1947 and has been the subject of further patents as methods for its production were improved. It is made by taking moist alginic acid (20 percent or greater solids) that has been partially reacted with sodium carbonate, and treating it with liquid propylene oxide in a pressure vessel for 2 hours at about 80°C. The product is dried and milled. Further details and references to the patents can be found in McHugh (1987).

5.2 Alginate producers

The capacities of alginate producers are summarized according to their broad geographical location and given in Table 5, and the principal alginate producers are listed below.
TABLE 5
Alginate processors. Capacity in tonnes (2001)

	Ca & acid process	PGA	Total	%
Europe	16 000	-	16 000	44
Africa	-	-	-	-
Americas	3 000	1 500	4 500	13
Asia-Pacific	14 000	1 600	15 600	43
Total	33 000	3 100	36 100

Source: H. Porse, CP Kelco ApS, 2002, pers. comm.

______________________________________ ISP Alginates (UK) Ltd
Waterfield
Tadworth
Surrey KT20 5HQ
United Kingdom
Tel: [INT+44] + (1737) 377 000
Fax: [INT+44] + (1737) 377148
Website: www.ispcorp.com/products/alginates
______________________________________
FMC Biopolymer
1735 Market Street
Philadelphia PA 19103
United States of America
Tel: [INT+1] + (215) 299 6000
Fax: [INT+1] + (215) 299 5809
Websites: www.fmc.com;
www.fmcbiopolymer.com
______________________________________
Degussa Texturant Systems
Lise-Meitner-St.34
85354 Freising
Germany
Tel: [INT+49] + (8161) 548 266
Fax: [INT+49] + (8161) 548 582
Website: www.texturantsystems.com
______________________________________
Danisco Cultor
Edwin Rahrs Vej 38
8220 Brabrand
Denmark
Tel: [INT+45] + 89 43 50 00
Fax: [INT+45] + 86 25 06 81
Website: www.daniscocultor.com
______________________________________
Kimica Corporation
15-4 Uchikanda 2 - chome
Chiyoda-ku
Tokyo
Japan
Tel: [INT+81] + (3) 3252 8708
Fax: [INT+81] + (3) 3252 8704
Website: www.kimica.com
______________________________________
Fuji Chemical Industry Co Ltd
1570, Nakanoshima
Wakayama City
Japan
Tel: [INT+81] + (73) 423 1247
Fax: [INT+81] + (73) 431 3005
Website: www.waila.or.jp/kasei
______________________________________
Algisa, Compania Industrial de Alginatos S.A.
PO Box 51645
Santiago 1
Chile
Tel: [INT+56] + 2 738 7904
Fax: [INT+56] + 2 738 7038
______________________________________
China Seaweed Industrial Association
Room 203 - Building 18 Maizidian Street -
Chaoyang Dist. Beijing 100026
China
Tel: [INT+86] + 10 6419 5140
Fax: [INT+86] + 10 6419 5141
This seems to be sponsored by the Ministry of Fisheries and represents the alginate industry.

5.3 Alginate uses

The uses of alginates are based on three main properties. The first is their ability, when dissolved in water, to thicken the resulting solution (more technically described as their ability to increase the viscosity of aqueous solutions). The second is their ability to form gels; gels form when a calcium salt is added to a solution of sodium alginate in water. The gel forms by chemical reaction, the calcium displaces the sodium from the alginate, holds the long alginate molecules together and a gel is the result. No heat is required and the gels do not melt when heated. This is in contrast to the agar gels where the water must be heated to about 80°C to dissolve the agar and the gel forms when cooled below about 40°C. The third property of alginates is the ability to form films of sodium or calcium alginate and fibres of calcium alginates.
Alginate molecules are long chains that contain two different acidic components, abbreviated here for simplicity to M and G. The way in which these M and G units are arranged in the chain and the overall ratio, M/G, of the two units in a chain can vary from one species of seaweed to another. In other words all "alginates" are not necessarily the same. So some seaweeds may produce an alginate that gives a high viscosity when dissolved in water, others may yield a low viscosity alginate. The conditions of the extraction procedure can also affect viscosity, lowering it if conditions are too severe. All of this results in sellers normally offering a range of alginates with differing viscosities.
Similarly, the strength of the gel formed by the addition of calcium salts can vary from one alginate to another. Generally alginates with a higher content of G will give a stronger gel; such alginates are said to have a low M/G ratio.
Some examples: Macrocystis can gives a medium-viscosity alginate, or a high viscosity with a careful extraction procedure (lower temperature for the extraction). Sargassum usually gives a low viscosity product. Laminaria digitata gives a soft to medium strength gel, while Laminaria hyperborea and Durvillaea give strong gels. These are some of the reasons why alginate producers like to have a variety of seaweed sources, to match the alginate to the needs of particular applications.

5.3.1 Textile printing

In textile printing, alginates are used as thickeners for the paste containing the dye. These pastes may be applied to the fabric by either screen or roller printing equipment. Alginates became important thickeners with the advent of reactive dyes. These combine chemically with cellulose in the fabric. Many of the usual thickeners, such as starch, react with the reactive dyes, and this leads to lower colour yields and sometimes by-products that are not easily washed out. Alginates do not react with the dyes, they easily wash out of the finished textile and are the best thickeners for reactive dyes. Alginates are more expensive than starch and recently starch manufacturers have made efforts to produce modified starches that do not react with the reactive dyes, so it is becoming a more competitive market. This use of alginate represents a large market, but it is affected by economic recessions when there is often a fall in demand for clothing and textiles. The types of alginate required vary from medium-to-high viscosity with older screen printing equipment, to low viscosity if modern, high speed, roller printing is used. Textile printing accounts for about 50 percent of the global alginate market.

5.3.2 Food

The thickening property of alginate is useful in sauces and in syrups and toppings for ice cream. By thickening pie fillings with alginate, softening of the pastry by liquid from the filling is reduced. Addition of alginate can make icings non-sticky and allow the baked goods to be covered with plastic wrap. Water-in-oil emulsions such as mayonnaise and salad dressings are less likely to separate into their original oil and water phases if thickened with alginate. Sodium alginate is not useful when the emulsion is acidic, because insoluble alginic acid forms; for these applications propylene glycol alginate (PGA) is used since this is stable in mild acid conditions. Alginate improves the texture, body and sheen of yoghurt, but PGA is also used in the stabilization of milk proteins under acidic conditions, as found in some yoghurts. Some fruit drinks have fruit pulp added and it is preferable to keep this in suspension; addition of sodium alginate, or PGA in acidic conditions, can prevent sedimentation of the pulp. In chocolate milk, the cocoa can be kept in suspension by an alginate/phosphate mixture, although in this application it faces strong competition from carrageenan. Small amounts of alginate can thicken and stabilize whipped cream.
For more information about factors that affect the viscosity of alginate solutions, see King (1983: 132-141). This discusses the effects of concentration of alginate, its molecular weight, the presence of any calcium remaining in the alginate from the extraction process, pH, temperature and other salts. For a briefer discussion, see McHugh (1987) or Clare (1993).
Alginates have some applications that are not related to either their viscosity or gel properties. They act as stabilizers in ice cream; addition of alginate reduces the formation of ice crystals during freezing, giving a smooth product. This is especially important when ice cream softens between the supermarket and the home freezer; without alginate or similar stabilizer the refrozen ice cream develops large ice crystals, giving it an undesirable crunchy mouth feel. Alginate also reduces the rate at which the ice cream will melt. Beer drinkers prefer some foam on the top of a newly-poured glass, and a poor foam leads to a subjective judgement that the beer is poor quality. Addition of a very low concentration of propylene glycol alginate will provide a stable, longer lasting beer foam. A variety of agents are used in the clarification of wine and removal of unwanted colouring - wine fining - but in more difficult cases it has been found that the addition of sodium alginate can be effective.
The gelling properties of alginate were used in the first production of artificial cherries in 1946. A flavoured, coloured solution of sodium alginate was allowed to fall, in large drops, into a solution of a calcium salt. Calcium alginate immediately formed as a skin on the outside of the drop and when the drop was allowed to sit in the solution, the calcium gradually penetrated the drop converting it all into a gel that hardened with further standing. Because the cherry-flavoured gels did not melt, they became very popular in bakery products. Fruit substitutes can now be made by automated and continuous processes that are based on similar principles. Either the calcium can be applied externally, as above, or internally. In the latter case a calcium salt that does not dissolve is added to the fruit puree, together with a weak acid; the weak acid slowly attacks the calcium salt and releases water-soluble calcium that then reacts with the alginate and forms the gel.
Edible dessert jellies can be formed from alginate-calcium mixtures, often promoted as instant jellies or desserts because they are formed simply by mixing the powders with water or milk, no heat being required. Because they do not melt, alginate jellies have a different, firmer mouth feel when compared to gelatin jellies, which can be made to soften and melt at body temperature. Mixtures of calcium salts and sodium alginate can be made to set to a gel at different rates, depending on the rate at which the calcium salt dissolves. Gel formation can also be delayed even after everything is mixed together; this is done using a gel-retarder that reacts with the calcium before the alginate does, so no calcium is available to the alginate until all the retarder is used. In this way gel formation can be delayed for several minutes if desired, such as when other ingredients need to be added and mixed before the gel starts to set.
Alginate gels are used in re-structured or re-formed food products. For example, re-structured meats can be made by taking meat pieces, binding them together and shaping them to resemble usual cuts of meat, such as nuggets, roasts, meat loaves, even steaks. The binder can be a powder of sodium alginate, calcium carbonate, lactic acid and calcium lactate. When mixed with the raw meat they form a calcium alginate gel that binds the meat pieces together. This is used for meats for human consumption, such as chicken nuggets; it has become especially useful in making loaves of meat for fresh pet food; some abattoir wastes are suitable and cheap ingredients. Up to 1 percent alginate is used. Similar principles are applied to making shrimp substitutes using alginate, proteins such as soy protein concentrate, and flavours. The mixture is extruded into a calcium chloride bath to form edible fibres which are chopped, coated with sodium alginate and shaped in a mould. Restructured fish fillets have been made using minced fish and a calcium alginate gel. Onion rings are made from dried onion powder; pimento olive fillings are made using pimento pulp. In 2001, a new line of olives launched in Spain were stuffed with flavoured pastes, such as garlic, herbs, hot pepper, lemon and cheese. Each of these is made with green manzanilla olives and an alginate-based paste containing the appropriate ingredient to provide the flavour.
Calcium alginate films and coatings have been used to help preserve frozen fish. The oils in oily fish such as herring and mackerel can become rancid through oxidation even when quick frozen and stored at low temperatures. If the fish is frozen in a calcium alginate jelly, the fish is protected from the air and rancidity from oxidation is very limited. The jelly thaws with the fish so they are easily separated. If beef cuts are coated with calcium alginate films before freezing, the meat juices released during thaw are re-absorbed into the meat and the coating also helps to protect the meat from bacterial contamination. If desired, the calcium alginate coating can be removed by re-dissolving it with sodium polyphosphate.
For further details
For more information about alginate gels, how they form, calcium salts to use, retardants, acid-release agents, and effect of alginates from different seaweeds, the most thorough discussion is to be found in King (1983: 141-154). While this may appear to be an old reference, these basics of gel formation are still the same. Other, briefer, treatments of gel formation are available in Clare (1993), Nussinovitch (1997) or Onsoyen (1997).
Re-structured foods are discussed in Chapter 20 in Nussinovitch (1997).
A brief tabular summary of alginate applications in food can be found in Onsoyen (1997).

5.3.3 Immobilized biocatalysts

Many commercial chemical syntheses and conversions are best carried out using biocatalysts such as enzymes or active whole cells. Examples include the use of enzymes for the conversion of glucose to fructose, the production of L-amino acids for use in foods, the synthesis of new penicillins after hydrolysis of penicillin G, the use of whole cells for the conversion of starch to ethanol (for beer brewing), and the continuous production of yoghurt. To carry out these processes on a moderate to large scale, the biocatalysts must be in a concentrated form and be recoverable from the process for re-use.
This can be achieved by "immobilizing" the enzymes or cells by entrapping them in a material that will still allow penetration by the substance to be converted or changed. Originally, single enzymes were isolated and used for a specific conversion, but now similar or better results can be obtained using whole cells, and this is more economical. An added advantage of immobilization is that the cells last longer. Ordinary suspended cells may have good activity for only 1-2 days, while immobilized cells can last for 30 days. Beads made with calcium alginate were one of the first materials to be used for immobilization. The whole cells are suspended in a solution of sodium alginate and this is added dropwise to a calcium chloride solution. The beads form in much the same way as described for artificial cherries. In use, they are packed into a column and a solution of the substance to be converted is fed into the top of the column and allowed to flow through the bed of beads containing the immobilized biocatalyst in the cells. The conversion takes place and the product comes out at the bottom. A simple example is to immobilize yeast cells, flow a solution of sugar through the beads, and the sugar is converted to alcohol.
For further details
Details of methods for making immobilized materials using alginates are available from alginate manufacturers (such as FMC Biopolymers, ISP Alginates, etc.). Today, many other materials besides alginate are used for immobilization. Nussinovitch (1997), in Chapter 15, discusses immobilization by a variety of polymers, including alginate, and gives many examples of its applications.

5.3.4 Pharmaceutical and medical uses

If a fine jet of sodium alginate solution is forced into a bath of a calcium chloride solution, calcium alginate is formed as fibres. If low viscosity alginates are used, a strong solution can be used without any viscosity problems and the calcium bath is not diluted as rapidly. The fibres have very good strength when both wet and dry. As with most polymer fibres formed by extrusion, stretching while forming increases the linearity of the polymer chains and the strength of the fibre. Good quality stable fibres have been produced from mixed salts of sodium and calcium alginate, and processed into non-woven fabric that is used in wound dressings. They have very good wound healing and haemostatic properties and can be absorbed by body fluids because the calcium in the fibre is exchanged for sodium from the body fluid to give a soluble sodium alginate. This also makes it easy to remove these dressings from large open wounds or burns since they do not adhere to the wound. Removal can be assisted by applying saline solutions to the dressing to ensure its conversion to soluble sodium alginate. Recently, the consumer division of a multinational pharmaceutical company launched a new line of adhesive bandages and gauze pads based on calcium alginate fibres. They are being promoted as helping blood to clot faster - twice as fast as their older, well established product.
Alginic acid powder swells when wetted with water. This has led to its use as a tablet disintegrant for some specialized applications. Alginic acid has also been used in some dietary foods, such as biscuits; it swells in the stomach and, if sufficient is taken, it gives a "full" feeling so the person is dissuaded from further eating. The same property of swelling has been used in products such as Gavisconä tablets, which are taken to relieve heartburn and acid indigestion. The swollen alginic acid helps to keep the gastric contents in place and reduce the likelihood of reflux irritating the lining of the oesophagus.
Alginate is used in the controlled release of medicinal drugs and other chemicals. In some applications, the active ingredient is placed in a calcium alginate bead and slowly released as the bead is exposed in the appropriate environment. More recently, oral controlled-release systems involving alginate microspheres, sometimes coated with chitosan to improve the mechanical strength, have been tested as a way of delivering various drugs. Pronova Biomedical AS, a leading supplier of ultra-pure alginates and chitosans for controlled release and other medical materials applications, was acquired by FMC Bioploymer in early 2002; FMC had previously acquired Pronova Biopolymer, producer of food and technical grade alginates.

5.3.5 Other applications

Paper
The main use for alginate in the paper industry is in surface sizing. Alginate added to the normal starch sizing gives a smooth continuous film and a surface with less fluffing. The oil resistance of alginate films give a size with better oil resistance and enhances greaseproof properties. An improved gloss is obtained with high gloss inks. If papers or boards are to be waxed, alginate in the size will keep the wax mainly at the surface. They give better coating runability than other thickeners, especially in hot, on-machine coating applications. Alginates are also excellent film formers and improve ink holdout and printability. The quantity of alginate used is usually 5-10 percent of the weight of starch in the size.
Alginate is also used in starch adhesives for making corrugated boards because it stabilizes the viscosity of the adhesive and allows control of its rate of penetration. One percent sodium alginate, based on the weight of starch used, is usually sufficient.
Paper coating methods and equipment have developed significantly since the late 1950s with the demand for a moderately priced coated paper for high quality printing. Trailing blade coating equipment runs at 1 000 m/minute or more, so the coating material, usually clay plus a synthetic latex binder, must have consistent rheological properties under the conditions of coating. Up to 1 percent alginate will prevent change in viscosity of the coating suspension under the high shear conditions where it contacts the roller. The alginate also helps to control water loss from the coating suspension into the paper, between the point where the coating is applied and the point where the excess is removed by the trailing blade. The viscosity of the coating suspension must not be allowed to increase by loss of water into the paper because this leads to uneven removal by the trailing blade and streaking of the coating. Medium to high viscosity alginates are used, at a rate of 0.4-0.8 percent of the clay solids. Because of the solvent resistance of alginate films, the print quality of the finished paper is improved.
Welding rods
Coatings are applied to welding rods or electrodes to act as a flux and to control the conditions in the immediate vicinity of the weld, such as temperature or oxygen and hydrogen availability. The dry ingredients of the coating are mixed with sodium silicate (water-glass) which gives some of the plasticity necessary for extrusion of the coating onto the rod; it also acts as the binder for the dried coating on the rod. However, the wet silicate has no binding action and does not provide sufficient lubrication to allow effective and smooth extrusion. An additional lubricant is needed, and a binder that will hold the damp mass together before extrusion and maintain the shape of the coating on the rod during drying and baking. Alginates are used to meet these requirements. The quantities of alginates used are very dependent on the type of welding rod being coated and the extrusion equipment being used. Alginate manufacturers are the best source of information for using alginates in welding rod applications.
Binders for fish feed
The worldwide growth in aquaculture has led to the use of crude alginate as a binder in salmon and other fish feeds, especially moist feed made from fresh waste fish mixed with various dry components. Alginate binding can lower consumption by up to 40 percent and pollution of culture ponds is sharply reduced.
Release agents
The poor adhesion of films of alginate to many surfaces, together with their insolubility in nonaqueous solvents, have led to their use as mould release agents, originally for plaster moulds and later in the forming of fibreglass plastics. Sodium alginate also makes a good coating for anti-tack paper, which is used as a release agent in the manufacture of synthetic resin decorative boards. Films of calcium alginate, formed in situ on a paper, have been used to separate decorative laminates after they have been formed in a hot-pressing system.

5.4 Markets and marketing of alginates

A summary of alginate markets is shown in Table 6. The total market has a value of about US$ 195 million.
There are difficulties and costs in the marketing of seaweed hydrocolloids, such as alginate, agar and carrageenan, which are not always apparent to those outside the industry. In some markets, one may compete with another; in others, one might be the only real choice. They must all compete, in at least some of their uses, with plant gums (such as guar and locust bean) and cellulose derivatives (such as carboxy methyl cellulose (CMC) and methyl cellulose) that are often cheaper. It is important to realize that price may not be the determining factor in a buyer's choice of a seaweed hydrocolloid; quality and its reproducibility from one batch to another may be more important. Frequently a buyer uses less than 1 percent of the hydrocolloid in his product, so a 20 percent price difference may be inconsequential in the total cost of a product. Many a buyer of seaweed hydrocolloids, satisfied with one particular brand or grade, will, despite a higher price, stay with it because the risks of changing may not seem to be worth the saving. So, in seaweed hydrocolloids, those brands already established in the market often hold a very strong, entrenched position. To dislodge them, a marketing group should include a strong technical team that can run tests and trials to convince the buyer of the equivalence of the new product; sometimes this requires a detailed knowledge of the buyer's industry. In promoting new sales, the hydrocolloid producer may have to provide complete formulations and technical know-how to potential buyers. Therefore selling costs of the seaweed hydrocolloids can be high and account must be taken of this by the potential producer.
The buyers of alginates fall into two groups. The first is a number of large buyers who know exactly what they want and who require little servicing because they have their own resources. This group includes those speciality gum companies who service smaller users by preparing their own blends of seaweed hydrocolloids and other hydrocolloids, according to the requirements of a particular customer.
The second and larger group are the smaller users who need some technical service support. Frequently this group yields more profitable sales in the long term because they may be sold specifically formulated products at a premium price and they are generally more reluctant to change to a competitor's product. At the same time, it takes more time and expense to establish such sales. Many of the major producers have such speciality products, shown by the large range of products listed by them.
Alginate manufacturers usually sell direct to the major markets, but in minor markets it is more economical to sell through an agent, leaving the task of market penetration to them, but providing technical support where necessary. Agents need to have an appreciation of the application of hydrocolloids and a knowledge of the client's industry. This ideal might be achieved by an agent selling a variety of chemicals to just one industry, like the food industry, but an agent who deals principally in hydrocolloids over a range of industries, which is a not uncommon situation, usually needs more backup from the producer. Large wholesalers or agents may buy from the producer and re-sell; otherwise they operate on a commission of 5-15 percent, depending partly on the degree of assistance required from the producer.
TABLE 6
Alginate markets (2001)

Application	tonnes	%
Food and pharmaceutical	10 000	33
All technical grades	20 000	67
Total	30 000

Source: H. Porse, CP Kelco ApS, 2002, pers. comm.

The above paragraphs are based on McHugh (1987), but the statements made are just as valid at the time of writing.

5.5 Future prospects

The overall annual growth rate for alginates is 2-3 percent, with textile printing applications accounting for about half of the global market. However, the textile industry is flat at present, as it rides a trough in the cycle of peaks and troughs, and it is 90 percent based in Asia and the Near East (Turkey). Pharmaceutical and medical uses are about 20 percent by value of the market and have stayed buoyant, with 2-4 percent annual growth rates, driven by ongoing developments in controlled release technologies and the use of alginates in wound care applications. Food applications are worth about 20 percent of the market. That sector has been growing only slowly, and recently has grown at only 1-2 percent annually. The paper industry takes about 5 percent and the sector is very competitive, not increasing but just holding its own. The alginate industry faces strong competition from Chinese producers, whose prices do not reflect the real expense of cultivating Laminaria japonica, even in China, yet they do not appear to import sufficient wild seaweeds to offset those costs. The result is low profitability for most of the industry, with the best opportunities lying in the high end of the market, such as pharmaceutical and medical applications.

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