41. The traditional uses of seaweed - as food and, to a lesser extent, as animal feed and fertilizer supplements - remain important, but in most parts of the world it is as raw materials for certain chemical products that marine algae are now chiefly valued. The especial role of seaweeds as food in the Far East and the prospects for a wider contribution by seaweeds to human nutrition generally are examined in a later section of this review. The present chapter, whilst also considering the use of seaweeds in animal feedstuffs and fertilizers, deals principally with the industrial products of present greatest economic importance - the phycocolloids agar, carrageenan, furcellaran and algin.1
1 See Appendix II
42. Although the production of a form of agar in Japan can be traced back several centuries, the commercialization of phycocolloids is a relatively modern development. The earlier industrialization of seaweeds began with the production of soda and potash from the ash of burned brown seaweeds, used in the seventeenth and eighteenth centuries in the manufacture of soap and glass and in the nineteenth century as a source of iodine. Competition encountered from soda produced from certain coastal, salt-rich plants and the discovery in 1873 of rich sources of iodine in Chilean mineral deposits eventually brought a severe decline in the kelp industry and, notwithstanding a brief impetus provided by the first world war, the production of potash and iodine from seaweed is unlikely to be revived. The discovery of algin by Stanford in the early 1880s, however, led to renewed and ultimately vastly increased industrial use of the brown seaweed resources.
43. Agar is a marine colloid extracted from certain algae of the class Rhodophyceae. It is insoluble in cold water but soluble in boiling water to make a liquid which, when cooled, forms a firm, clear, resilient gel possessing suspending, stabilizing and thickening properties.
44. The terms agar and agar agar are often applied in a rather loose and confusing manner. The word itself is of Malayan origin and in that language refers to seaweeds such as Gracilaria, which yield a jelly used for making sweetmeats. The terms are, however, frequently and incorrectly used to describe any gum of seaweed origin.2 A strict chemical definition of agar is not presently possible as it is prepared from a number of different red algae, or mixtures thereof, and its composition varies. However, it is now generally agreed that the use of the term agar should be confined to the dried extract and even here it should be used in the generic sense.
2 To add further to the confusion, the term “agar” is also sometimes used to describe dried seaweed of agar-bearing species.
45. First valued primarily as a food supplement in the Orient, agar was originally a simple jelly obtained by boiling seaweed. The forerunner of today's commercial product was discovered quite accidentally in about 1660 when, according to legend, a Japanese innkeeper one winter night threw some surplus seaweed jelly outdoors. After several nights and days of alternately freezing and thawing, the jelly turned into a papery, translucent substance which the innkeeper found could be reboiled in water and cooled to yield a gel equal to the original. This was the beginning of a cottage industry, a winter occupation for fishing families, and the development of the manufacture and marketing of agar in the form of sheets, bars, sticks and other shapes, known in Japan as “Kanten”.
46. The traditional Japanese process involves the following steps:
the careful blending of up to six or seven different types of red seaweed, selected according to the desired flexibility, density, smoothness, solidity and resilience of the end product;
extraction in open iron cauldrons of boiling water, tough seaweeds (e.g., Gelidium) being introduced first, the softest (e.g., Gracilaria) last;
adjustment of the pH to 5–6 by treating the mixture with sulphuric acid;
simmering of the mixture for between four and ten hours, after which weak liquor from the previous day's extraction is added, followed by further cooking for up to a total of 12 to 15 hours;
a bleaching agent (e.g., hypochloride, hydrosulphite or bisulphite) is also introduced, in some processes after the addition of the weak liquor, in others prior to the final filtering;
straining through wire mesh or cloths of various degrees of fineness, usually under pressure;
a second boiling of about ten hours;
a second filtering after which the liquor is poured into wooden trays to cool and jellify;
cutting of the gel into suitable shapes and sizes and placing them outdoors on straw mats;
successive freezing and thawing for three to six days. Each day some of the night-formed ice melts, the drainings carrying away some salts, residual colour and other impurities; the lost moisture is partially restored by sprinkling with water;
drying in the sun for a further 15 to 30 days;
packing, either in strips or threads, or in a shredded or powdered form;
grading at official inspection centres, according to colour, lustre, gel strength, etc. The commercial product is white, shiny and semi-transparent, tasteless and odourless.
47. The whole process demands great care, particularly in the selection of raw materials and in the site of the locality; experience, especially in how to counter the effects of climatic changes; and not a little luck.
48. Using these techniques, commercial production of agar was established in Japan in the late seventeenth century and remained a uniquely Japanese activity for nearly two centuries until manufacture began in China and the Malay peninsula. Irregular production subsequently occurred in Sri Lanka, India, Australia and Indonesia, but at the advent of the second world war, Japan, with over 500 establishments in operation, remained by far the most important single producer of agar. Since agar is of considerable importance in bacteriological work, the war sparked off intensive efforts in many parts of the world to try to fill the gap created by the withdrawal of Japanese supplies.
49. The majority of Japanese agar is still produced by traditional methods but more scientific technology has now been introduced not only in Japan but also by most of the new producers who have entered the industry over the last 30 to 40 years. The modern processes are generally more sophisticated adaptations of the basic extraction - freezing - thawing - drying method and include artificial refrigeration to control freezing and thawing rates and other mechanical and chemical controls over quality and yield. Since the 1940s plants have been established in New Zealand, South Africa, U.S.S.R., Denmark, U.S.A., Argentina, Chile, Mexico, Republic of Korea, Morocco, Portugal, Spain, France, Italy and India. Output has grown particularly rapidly in Spain but Japan still retains its position as the world's leading producer of agar. Total world production of agar is now believed to exceed 7 500 tons per annum, compared with an earlier estimate of 3 500 tons in 1958 (see Table IV).
50. In common with other, less costly vegetable gums, agar possesses the qualities of suspending, thickening, stabilizing and gelling aqueous preparations. Its specific applications, however, arise from more particular properties which set it apart from other gums. These peculiar qualities include high gel strength at very low concentrations (a one percent solution of superior grade Gelidium-type agar gels at 35°C to 50°C and melts at 80°C to 100°C), low viscosity in solution and transparency. In particular these attributes make top quality agar almost uniquely valuable for use in microbiology.
51. The use of agar in microbiological culture work is particularly important in the U.S.A., where, out of a total consumption of some 450 tons of agar annually, about 40 percent is used for this purpose. No other gelling agent is so aptly suited for use as an all-purpose culture medium.1 It is non-toxic, resists liquification, can be sterilized repeatedly without losing its other properties, it remains liquid when cooled to 42°C, thus permitting the thorough distribution of organisms at a temperature which will not harm them and once set can be kept at incubation temperatures without melting.
1 Silverthorne and Sorensen (1971)
52. Notwithstanding the importance of this particular form of application, outside the U.S.A. larger quantities of agar are employed in other uses, notably in food processing. Although agar is practically indigestible, its properties as an emulsifying, stabilizing and gelling agent encourage extensive use in many food products.2 Agar is employed in the manufacture of ice-cream, cream cheeses, yoghourts, confections such as marshmallows, jellied sweets, a wide range of bakery products, vegetarian and health foods, soups and sauces. In certain western countries, agar is also highly valued as a clarifying agent in the preparation of beers, wines and coffee. Another food industry application of considerable importance is in canning, where it is used as a firm jelly to prevent transit damage to the preserved, cooked meat or fish. In this context, it is notable that in the U.K. the single greatest application of agar and other red seaweed phycocolloids is believed to be in the preparation of canned meat and fish products for the pet food market, consumption for this use alone being of the order of several hundred tons per year.
2 For a full list of food applications of agar (and other phycocolloids) see Chapman (1970), pp. 143–4
Estimated Production of Agar Agar 1958, 1968 and 1973
|Japan||1 500||3 025b||(3 000)|
|Korea, Rep. of||300||415c||500c|
|Total (approx.)||3 470||6 850||7 590|
a Estimates ex-Whistler, 1973
b Okazaki, 1971
c Based upon export data
d 1970 (Silverthorne and Sorensen, 1971)
e Not included in Whistler estimate
* Included in “Others”
53. Agar's use as a direct food ingredient is confined to Japan, China and southeast Asia, principally in the form of a jelly supplement to rice, vegetable and fish dishes.
Agar - Average Unit Values in International Trade 1970–1974 U.S.$ per kilogram
|Germany, Fed. Rep. of||3.50||3.69||4.05||7.35||12.70|
|Korea, Rep. of||3.53||3.41||3.33||6.75||8.00|
Source: National statistics of imports and exports (value - quantity) converted into U.S.$ at then current exchange rates
54. Agar has also been found valuable in a host of industrial applications, for example in the manufacture of accurate casts of objects where more rigid materials cannot be used (dentistry, plastic surgery, tool-making, criminology, etc.). In the cosmetic industry, agar is used as a stabilizer for emulsions, and as a constituent of skin creams, ointments, lotions, etc.1 Other applications are found in the photographic industry, in paper manufacture and in the textile industry as a finishing and sizing agent. Chapman (1970) also notes uses in the production of linoleum and artificial leathers; as a sound and heat insulator; as an ingredient for paints and in the manufacture of storage batteries for submarines.
1 Levring, Hoppe and Schmid (1969)
55. In the medicine and pharmaceutical fields, agar serves a major market in branded laxative products. It has also been used in connexion with wound dressings, as an anti-coagulant and one of its earliest uses in the East was in treating gastro-intestinal disorders.
56. Agar prices have fluctuated, to a certain degree cyclically, over the last three decades, variations in raw material supplies and in end-use demands bein the principal factors. Prices also vary at any particular time according to the source of the product and its quality. The grades of agar are in fact diverse and their qualities depend not only upon the individual seaweed species (and mixture thereof) used, their geographic origin and season of harvesting, but also upon the drying and processing methods employed and the nature of the products themselves (bars, powders, flakes, etc.).
57. Such fluctuations, however, generally remained within the range of about U.S.$ 3 to U.S.$ 5 per kg until 1973, which was marked by a very rapid increase in international prices for agar. The rise in unit values continued during 1974 and, whilst trading in agar appears recently to have been at a very depressed level, offer prices in 1975 have shown little decline. The background to this remarkable increase is more fully discussed in a later section of this paper (see page 41) but the general evolution of agar prices in the early 1970s is indicated in Table V.
58. The phycocolloid carrageenan,1 like agar, is a polysaccharide extract derived from certain species of red algae and is soluble in water. It has, however, specific properties which distinguish it, chemically and in range of applications, from agar.
1 Sometimes also called, imprecisely, carragheenan, carrageenin or Irish moss extract, and often included in trade statistics as “agar”
59. The principal raw materials used in the extraction of carrageenan are Chondrus crispus and, to a lesser extent, Gigartina stellata, species which are especially abundant on the Atlantic costs of Europe and North America, notably Canada. There is considerable trade in dried weed, especially from Canada, to the U.S.A. and Denmark. Increased demands for the end product, growing competition for raw materials (both in general and for specific species) and heavy exploitation of traditional resources have reinforced this tendency to transport weed over greater distances; they have also encouraged the use of other red seaweeds such as Eucheuma species, which principally occur in regions remote from the major processors, for example, East Africa, Indonesia, The Philippines and Malaysia.
60. Carrageenan is a complex mixture of several polysaccharides, the relative amounts and composition of which vary with the type of seaweed used.2 It has now been established that carrageenan can be separated by means of potassium ions into two main components; an insoluble fraction (termed Kappa-carrageenan) and a soluble fraction (termed Lambda-carrageenan).3 The former forms brittle gels, the latter viscous, non-gelling solutions; both contain a minimum of 20 percent of sulphate, compared with agar which averages about 3 percent. An extensive range of carrageenans of divergent and, in some cases, unique properties can thus be produced by chemical modification, their characteristics being tailored to suit the needs of individual applications or particular customers. This ability to produce carrageenans to standardized specifications,4 allied with competitive and relatively stable prices, has led to a rapid expansion in its usage over the last two decades.
2 Towle, G.A., In Whistler (1973)
3 A third fraction, iota-carrageenan, is yielded by certain Eucheuma species, in particular E. spinosom. It has different physical properties to K- and λ -carrageenans; for example, i-carrageenan will develop tough elastic gels when mixed with calcium salts, and rigid gels when mixed with potassium salts. Because of these qualities i-carrageenan is particularly valued in various products such as dietary and low calorie gels and is in increasing demand (Dawes, 1974)
4 Compared with agar, where the gel strength, for example, can often only be established by empirical post-production testing
61. In principle, the production of carrageenan is a simple process of extraction, purification and precipitation. In industrial practice, however, the process if quite complicated and subject to extensive technical refinements and quality control procedures. Towle1 notes that the methods used in processing, as well as in the selection and blending of raw materials, vary widely from producer to producer and are for the most part closely guarded trade secrets. The following outline of the steps involved, based upon a description2 of procedures employed by the major Danish producer, may serve as an example:
washing the selected seaweeds to remove impurities;
extraction with hot water and some alkaline chemicals, occasionally under pressure, for several hours;
separation of seaweed residue by means of a coarse filtration or in a centrifugation process. Because of the high viscosity a filter aid such as cellulose is used;
a further filtering or “polishing” to remove the fine insoluble impurities, again in the presence of a filter aid, normally, diatomaceous earth;
the extract - which is now sparkling clear and contains about one percent of carrageenan - is concentrated in multi-stage evaporators to a concentration of two to three percent and the carrageenan is precipitated by adding alcohol to the extract (note: the “freeze-out” method used for agar can also be applied in modified form).3
the precipitated carrageenan is dried to remove excess alcohol;
the dried product is milled into a fine powder, either white to light beige in colour, and odourless;
the powder, after quality control and laboratory checks, is then blended and packed in polyethylene bags inside fibre drums for shipping.
1 In Whistler (1973)
2 Nielson, 1971
3 J. Christensen, personal communication
62. Although Irish Moss had been valued for many centuries as a fertilizer, simple medicine and in foods (where its remarkable milk reactivity, for example, in the preparation of blancmanges, was quickly noted), it was not until the early twentieth century that commercial production of the extract was attempted.4 The shortages of wartime promoted a very rapid increase in the output of carrageenan in the 1940s, a growth subsequently maintained by the rising demands of peacetime and by new applications.
4 Towle, G.A., In Whistler (1973)
63. The main centres of the extraction industry are the U.S.A. (predominantly), Denmark and France; small quantities of carrageenan are also produced in the U.K., Norway, Spain, Morocco, Canada and Japan. A feature of the industry is its concentration in the hands of a very small number of companies. As a result of this highly competitive situation, data on carrageenan production are not easily available and published estimates are rather conflicting. Towle estimated that world output in 1971 was approximately 4 500 metric tons, of which 2 300 tons were attributable to the U.S.A. Silverthorne and Sorensen (1971), however, in the light of their estimates of world harvests and expected yields of the several species involved, assessed the world's production of carrageenan to be nearly twice that estimated by Towle, i.e., about 8 640 tons, of which 3 860 tons produced in the U.S.A. Dawes (1974) suggested that output in 1974 may well have been over 10 000 tons, but coincidentally refers to an indication, in a personal communication from the major U.S. producer, that 1973 world output was only 8 000 tons. By contrast, however, a representative of the same company1, writing in 1973, reported that “annual world production of carrageenan is over 6 000 tons”; in the same paper it was estimated that the “present world market for carrageenan-containing weeds is about 18 000 tons (dry weight) per year.” The latter indicates, on the basis of a yield of between 60 and 70 kg of carrageenan per 100 kg of dry weed, a total market for carrageenan of between 11 000 and 12 500 tons per annum. Related to the preceding estimate of current annual production of carrageenan, this figure must be assumed to be an assessment of potential demand for the gum, implying a shortfall between supply and demand.
1 Parker, H.W. (1974)
64. An evaluation of the limited data presently available regarding worldwide production of carrageenan-bearing seaweeds (see Table VI) tends to corroborate those estimates suggesting that carrageenan output in the early 1970s has been of the order of 8 000 to 9 000 tons per annum, and that extractors had severe difficulties in obtaining sufficient raw materials to increase their output to meet rising demands. The harvest of red seaweeds usable in carrageenan production appears to have averaged about 65 000 tons (wet basis) over 1971–73; this would imply a dry weed supply of some 13 000 tons and a potential yield of between 8 000 and 9 000 tons of carrageenan gum. The success in The Philippines with Eucheuma culture and a big Canadian crop of Chondrus very considerably boosted 1974 supplies of weed and a buyer's market persisted throughout 1975.2
2 Warehouse stocks of carrageenan-bearing seaweeds were estimated to have declined to under 1 200 tons by end April 1976, compared with some 2 000–3 000 tons at the close of 1974 (Maxwell S. Doty, personal communication)
65. The strong demand for, and shortage of, Chondrus and other carrageenan-bearing seaweeds resulted in a fairly consistent and, ultimately, substantial rise in processor's raw material costs. Clean, dried Canadian Chondrus crispus, for example, was obtainable in 1963 at around U.S.$ 0.22 per kg, rose to U.S.$ 0.37 per kg by 1970 and in 1973 had reached a level of U.S.$ 0.66 or more (depending upon the purity of the sample). Prices paid for processed carrageenan, on the other hand, have risen much less sharply than weed costs, values in 1973 being on average3 about U.S.$ 4.5 per kg compared with some U.S.$ 3.3 per kg ten years earlier. As Silverthorne and Sorensen observed, economies in processing methods appear to have absorbed some of the rising costs of raw materials.
3 Prices for particular carrageenans vary considerably according to grade, end-use, specification, etc.
66. This relative stability in carrageenan prices, together with its unique properties and its capacity to be employed at very low concentrations, make carrageenan a very important competitor in the diverse market for gums. Of the algal hydrocolloids, it has by far the widest food industry applications. It has many uses in common with agar, for example, in dairy products, in the manufacture of various beverages and bakery products, in meat and fish canning. However, carrageenan's properties as a thickener, stabilizer and gelling agent are strongly influenced by the materials with which it is mixed. It is thus very extensively used, with notable cost economy, in a range of milk products because of its particular reaction with casein. As already noted, i-carrageenan has special value in the preparation of dietetic foods. New uses for carrageenan are continually being developed, for example, in salad dressings and sauces, as a coating for frozen food products and as a batter ingredient.4
4 Towle, G.A., In Whistler (1973)
67. Carrageenan is not as widely used in pharmaceutical products as agar, nor has as many industrial applications as algin. Nevertheless, it is employed in the production of toothpastes, dental powders and insoluble drug preparations, in industrial suspensions (for example, water paints) and as a stiffener and binder in textile and leather manufacture.
Estimated Production of Carrageenan-Bearing Seaweeds
|'000 tons wet weight|
a Data reported to FAO, all red seaweeds
b OECD data
c Official data for dried weight basis converted (at 1:5) to wet basis; in the case of Indonesia, it is assumed that exports of red algae consisted mainly of Eucheuma.
d Official export data
e Estimates provided by FAO/UNDP project
f Official production data
g Caces-Borja (1974)
h January/August only
i Estimate based on Silverthorne and Sorensen (1970)
68. In the course of the last 30 years a new phycocolloid, furcellaran, has gained an important position in the gum market. Based on the red seaweed Furcellaria fastigiata, which is present along many coasts of the North Atlantic and its adjacent seas, but above all in the Kattegat, it began as a substitute for agar but has found many special uses as a gelling and thickening agent. Although originally known as Danish agar, its properties most closely resemble those of K-type carrageenan.1
69. Production of this phycocolloid is centred in Denmark, although there is evidence of at least experimental extraction in Poland2 and the likelihood of commercial processing in the U.S.S.R.3 Between 20 000 and 30 000 tons (wet weight) of locally harvested Furcellaria and imports from Canada are now processed each year in Denmark. Output of furcellaran has risen steadily from about 100 tons in 1950, to around 500 tons per annum by the mid 1950s and reached between 700 and 1 000 tons annually during the 1960s. In recent years, production has been of the order of 1 200 per annum, prices varying between U.S.$ 3.20 and U.S.$ 5.0 per kg.1
1 Bjerre-Petersen, Christensen and Hemmingsen, In Whistler (1973)
2 Czapke (1961)
3 Levring, Hoppe and Schmid (1969)
70. This growth in production has been achieved not only by bigger harvests but by improved processing efficiency, permitting yields of 1 kg of furcellaran per 25 kg of (wet) weed, compared with 40 kg of weed in the earlier stages of development.4
4 Lund and Bjerre-Petersen (1961)
71. The processing methods, which are not dissimilar to modern agar processing techniques, are described in Whistler (1973) as follows:
the washed Furcellaria is pre-treated in concrete tanks with an alkaline solution for one or two weeks. If immediate extraction is not envisaged, the pre-treated weed can be dried and stored;
the weed is boiled in water, either in open vessels or pressure cookers, and the extract obtained by filtration and centrifugation;
the extract is concentrated by vacuum evaporization and precipitated as gelled threads by a solution of potassium chloride;
the threads are drained and frozen in a brine freezer for 20–30 hours;
after thawing in a potassium chloride solution, the gel precipitate is pressed or centrifuged into a fibrous mass containing about 15 percent dry substance;
the material is dried, ground and sifted into a powder;
standardized products can then be made by blending different batches and additives.
72. Furcellaran has become of particular importance in the production of milk pudding powders and fruit and other jellies. Over 90 percent of total output of the gum is used in food products, including jams and other preserves, fruit juices, meat and fish preparations and in beer brewing. It is also used in the cosmetic industry, especially for toothpastes, and in dietetic and baby food preparations. A notable feature is the successful combination of furcellaran with other gums or thickening agents, such as carrageenan, locust bean gum, guar gum and sucrose, to produce gelling products with special properties.
73. The term “algin” is a generic name for the salts of alginic acid and is most commonly applied to the sodium salt, sodium alginate.1 Algin has been found in all the larger seaweeds studied but commercial production is based principally upon Macrocystis pyrifera, Ascophyllum nodosum and a number of Laminaria spp. Most notable of the other, lesser sources of algin are certain species of Ecklonia, Nereocystis, Sargassum and Fucus. The algin content of the various brown algae varies, the highest values (35 to 47 percent of dry weight) being found in stipes of Laminaria digitata. Although the main species exploited, Macrocystis pyrifera, contains substantially less algin than many other seaweeds, its very large size and accessibility (permitting mechanical harvesting) make its use particularly economic.
1 Other commercially important algins are the potassium, ammonium and propylene glycol alginates
74. The technical importance of alginic acid lies mainly in the properties of its salts2 which dissolve readily in water to form an extremely viscous solution which can be further modified by the addition of specific chemicals. Algin's unique properties as a thickening, stabilizing, suspending, film-forming, gelling and emulsifying agent have resulted in an unusually wide range of industrial, pharmaceutical and food applications.
2 Chapman (1970)
75. A variety of processing materials are used commercially to produce algin, but a typical extraction process would be as follows:3
the weed is washed and then digested with an alkali such as sodium carbonate;
cellulose is removed by flotation;
after filtration, the algin is recovered from the solution by precipitation;
the calcium alginate precipitate is then converted into alginic acid by means of an acid wash;
the alginic acid is neutralized with appropriate alkalies to produce the desired alginate salt;
the algin is dried, milled, tested and blended for specific viscosity range or function.
3 Based upon McNeely, W.H. and Pettitt, D.J. In Whistler (1973) and Rees, W.M. In Firth (1969)
76. Commercial production of algin began in the U.S.A. and the U.K. in the early 1930s; important industries have subsequently been developed in Norway, France and Japan, and some algin is also produced in Canada, Spain, Morocco, Chile, India, Brazil and the U.S.S.R. Stevens (1971) notes proposals for the establishment of plants in the Falkland Islands and Bulgaria.4
4 During the period 1963–1973 kelp resources off the east coast of Tasmania were commercially exploited for alginate production. Operations have now ceased as a result of the rising costs of harvesting declining resources (Australian Department of Agriculture, October 1975). However, a new Anglo-Australian company has been formed to exploit the kelp resources of the Bass Strait, between Tasmania and Australia (“France Pêche”, (207), Feb.1976)
77. Again, reliable “official” data relating to world output of algin are not available and the estimates quoted in the literature are rather conflicting. Silverthorne and Sorensen (1971) concluded that world algin production in 1970 was approximately 12 800 tons and, taking an average price of U.S.$ 1.25 per lb, valued at some U.S.$ 35 million. The same total for 1970 was quoted by Pérès (1973), who attributed 4 500 tons to the U.S.A., 3 000 tons to the U.K., 2 500 tons to Norway and between 1 200 and 2 000 tons to France.1 Frequently noted but rather suspect estimates for 1958 by Von Haken (1958) indicated a then output of algin between 7 000 and 8 000 tons, of which half was by the U.S.A. Commenting upon these figures, Woodward (1966) considered that it was reasonably certain that by 1965 alginate production was twice that of 1958. Chapman (1970) also suggested that algin production in the mid 1960s was double that of 1958, indicating an output of 14 000 tons in 1964, of which one third to a half was by the U.S.A., 2 000 tons from the U.K. and 800 tons from Norway. Stevens (1971) estimated that the world market for alginates in 1970 was about U.S.$ 50 million in value (which at then current prices, would indicate a volume of 18 000 to 19 000 tons).
1 No account appears to have been made of output in countries such as Japan, where over 1 300 tons of algin are produced annually, and the U.S.S.R., where production, although unknown, must be fairly substantial
78. The production of algin undoubtedly continued to expand in the course of the early 1970s.2 Whilst it is impossible to be precise, it seems reasonable to assume that world algin output must presently be at least of the order of (but probably greater than) 16 000 tons per annum (see Table VII).
2 For example, the annual turnover (in financial terms) of the major British producer rose by nearly 230 percent between 1969 and 1973. A new seaweed processing enterprise in Brazil is reported to have recently (1973?) produced nearly 1 000 tons of alginates (Michansk, personal communication)
79. This sustained growth in the demand for alginates has been positively influenced by the relative stability in ex-plant prices for algin. Because much of algin production is based on continuous, modern processing systems supported by mechanical harvesting of the raw material, prices for algin do not fluctuate in the same manner as those of some other natural water-soluble gums; according to the grade and composition, prices on the dominant U.S. market have tended to range between U.S.$ 1.00 and U.S.$ 2.00 per kg. It has been suggested that, if demand continues to rise as rapidly as in the past, algin producers will probably be faced with increasing raw materials costs; however, the cost of weed is only a small part of total production costs and, the widespread substitution of synthetics for algin being unlikely due to its highly complex structure and unique properties, the markets appear to be reasonably secure.3
3 Silverthorne and Sorensen (1971)
80. The markets for algin are indeed very extensive and no more than a brief description can be attempted here.4 Among a wide range of food industry applications, algin is perhaps of particular importance as a stabilizer in ice-cream manufacture and as a suspending agent in milk-shakes; about a half of the entire U.S. output of algin is reported to be used for such dairy produce purposes. Algin is also applied in bakery icings, cake and pie fillings and toppings, sauces and salad dressings, in wine, beer and fruit drink manufacture, in meat, sausage and fish preparations and in canned foods. In the pharmaceutical industry, algin is widely used as a binding agent for pills, pastils and ointments, in toothpastes and in dental and orthopaedic impression compounds. It is also a valuable auxiliary agent in the production of cosmetic creams, hair sprays, shampoos and soaps and as a foam stabilizer in the detergent industry.
4 For fuller reviews of the structure, qualities and applications of algin see McNeely, W.H. and Pettitt, P.J., In Whistler (1973); Levring, Hoppe and Schmid (1969) and Chapman (1970)
81. The various algins and alginate compounds are extremely widely applied in industry as emulsifiers, gelling, suspending and thickening agents, stabilizers, as film and filament formers and as protective colloids. The following is an illustrative and far from exhaustive list of such industrial applications: in paints and dyes, building materials (tar and asphalt, artificial wood, insulation products, sealing compounds, etc.), enamels and ceramics, fire-extinguishing foams, welding electrodes, filter and absorption substances, textile printing and finishing, later and other rubber products, paper products (in particular, cartons and wrapping materials), car polishes and cleaners, photographic coatings, insecticides and herbicides, adhesives, leather products, explosives, boiler-scaling compounds, oil drilling lubricants and coolants.
Approximate Annual Production of Alginates - Early 1970s
|U.S.A.||4 500 – 5 000|
|Norway||2 000 – 2 500|
|France||2 000 – 2 500|
|Korea, Rep. of||150|
|Others||2 000 – 2 500a|
|Total||16 000 – 17 000|
a Including U.S.S.R. (>1 000?), Brazil (<1 000?) (Author's estimates)
82. Agar, carrageenan, furcellaran and algin are by far the most important seaweed extracts in present commercial use. There are, however, a number of other seaweed products currently of minor significance, whose potential value merits a brief examination1 in this review.
1 For a fuller description of these and other minor phycocolloids, reference should be made to Levring, Hoppe and Schmid (1969), pp. 288–368; Sand, R.E. and Glickman, M., In Whistler (1973), Chapter IX; and Chapman (1970), Chapter 9
83. Four such products - hypnean, funoran, iridophycan and phyllophoran - are derived from certain species of red seaweeds.
84. Hypnean, which is often considered to be a type of carrageenan, is derived from Hypnea musciformis and related species. These weeds are fairly abundant in tropical waters, notably southern Florida, the Caribbean, the Gulf of Mexico, the northeast coast of Brazil, Australasia, parts of the South China Sea and South Africa; resources of potentially economic importance have also recently been identified in the Gulf of Oman. The extract normally has a gel strength far exceeding that of other phycocolloids; moreover, its properties are susceptible to a high degree of control and chemical modification. This ability to form, often in combination with other components, gels of very great firmness and elasticity, led to hopes that hypnean could become of considerable commercial importance. These hopes have not so far been realized chiefly because processors have experienced wide fluctuations in the quality of successive harvests of Hypnea.
85. Funoran is not an extract but is marketed in the form of dried, usually bleached, sheets of whole seaweed; when mixed with hot or lukewarm water the entire plant dissolves, giving a clear, viscous colloidal solution of excellent adhesive and sizing properties. Its use is mainly confined to eastern Asia, especially Japan and China. In the former its major application is as a constituent in hair waving and hair dyeing preparations. Funoran is also a paper and textile sizing agent, has widespread uses as a household adhesive and has long been valued in the traditionally delicate artwork of the region. The chief raw materials used are Gloiopeltis species which occur principally off Japan and China; resources are also present along the Pacific coasts of North America.
86. Iridophycan is an extract from species of the Iridea genera of algae, which are most prevalent in the waters off central California but also are present off South Africa, Japan, Chile and the Falkland Islands. Its uses are influenced by the similarity of its properties to those of funoran and carrageenan, for which it frequently serves as a dilutant or substitute.1 In the U.S.A. iridophycan has found particularly widespread use as a stabilizer for chocolate and other beverage mixes; it also serves as an excellent all-purpose adhesive and as a paper and textile size. As an aqueous extract, it has pharmaceutical value as an agent to prevent blood coagulation.
87. The red seaweed species Phyllophora is found on the coasts of many temperate and cold seas, including the eastern and western Atlantic, Baja California and Mexico, but is most abundant in the Black Sea where it provides the basis for an important phycocolloid industry in the U.S.S.R. The extract, phyllophoran, has properties intermediate between those of agar and carrageenan and, in general, its range of applications in the U.S.S.R. is very similar to those of agar and carrageenan in other countries.1
1 A number of authoritative observers have suggested that the terms “Iridophycan” and “Phyllophoran” should be abandoned and that the extracts should be regarded as carrageenans
88. Three minor extracts derived from brown seaweeds are also worthy of mention - laminaran, fucoidan and mannitol.
89. Laminaran is found in the fronds of Laminaria and, to a lesser extent, in Ascophyllum and Fucus species; the laminaran content varies seasonally and with the habitat of the weeds. The main Laminaria species that store laminaran occur off Norway, where resources are believed to approach 20 million tons (wet weight), Scotland, Ireland, France, Spain and eastern Canada. Commercial applications of the extract have so far been limited. Laminaran does not gel nor form any viscous solution and its main potential appears to lie in medical and pharmaceutical uses. It has been shown, for example, to be a safe surgical dusting powder, and may have value as a tumour-inhibiting agent and, in the form of a sulphate ester, as an anti-coagulant.
90. Fucoidan occurs in all brown algae in varying amounts; it is found in the intercellular tissues and is considered to be a substance used by the weeds to protect themselves against the effects of drying out when exposed. After extraction, fucoidan is extremely viscous, even in very low concentration, but is highly susceptible to aging, diluted acids and bases. This instability and its quality inconsistency have so far prevented the commercially significant development of fucoidan. However, it is generally agreed that, if success is eventually achieved in producing the product in stable, consistent form, it could become of considerable economic importance because of its excellent intrinsic physical properties.
|Fig. 13 Hypnea sp. (R)||Fig. 14 Fucus vesiculosus (Br.) “Rockweed”|
|Fig. 15 Alaria esculenta (Br.)||Fig. 16 Sargassum sp. (Br.)|
91. Mannitol is an important sugar alcohol which is present as a cell sap in a number of brown algae, especially in certain species of Laminaria and Ecklonia. The mannitol content of the weeds is subject to wide seasonal fluctuations and also depends upon the depths at which the weeds are growing. Applications of mannitol are extremely diverse. It is used in pharmaceuticals, in making chewing gum, in the paint and varnish industry, in leather and paper manufacture, in the plastics industry and in the production of explosives. The U.S.A., U.K., France and Japan are the main centres of production.
92. The use of seaweeds as an animal feed has a long history in coastal areas where the material is readily available. In recent times the practice has become more widespread by the establishment of processing plants to dry and grind the weed into a meal for use as an additive to stock feeds. These practices appear largely to be restricted to northern Europe - especially Norway, Denmark, Iceland, Ireland, Scotland and France - and parts of North America, although reference can be found to such uses in Hong Kong and the islands of the Bering Sea (Kirby, 1953), New Zealand (Chapman, 1970) and South Africa (Druehl, 1972).
93. A typical example of this use is given by Hallsen (1964) who describes the long tradition in Iceland of directly grazing sheep and, to a lesser extent, horses, on seaweedstrewn beaches. He notes, however, that there is no scientific proof of any especially beneficial effects upon fattening, wool production or fertility. The production of a seaweed meal in Iceland, based upon Ascophyllum nodosum, was first attempted in 1939/41 and restarted in 1960, the product being sold on the home market as a supplementary feed; incorporation of seaweed meal in the basic hay ration has been shown to improve the fertility of sheep but, in general, with less marked effect than with a supplement of herring meal.
94. In addition to the abundance of the basic raw materials (brown seaweeds, mainly Ascophyllum and Laminaria) seaweed meal is a rich source of minerals, vitamins and trace elements. Druehl (1972) noting that the literature abounds with testimonials to its benefits, estimated that world production is of the order of 50 000 tons per annum. This is probably an underestimate, production in Ireland alone being reported to be 35 000 to 40 000 tons in the mid 1960s (Chapman, 1970); Norway is also a substantial producer, and total world output may currently be of the order of 100 000 tons. The utilization value of seaweed meal has been shown to vary considerably, according to the species used and the type of animal fed; poor digestibility coefficients have, in a number of cases, created special problems. Black (1955) considered that seaweed meal could be included in the rations of most animals (including poultry) up to at least 10 percent without any detrimental effect, a conclusion supported by Chapman (1970) with the proviso that its use for pigs does not seem desirable and that further work on sheep breeds is necessary. Silverthorne and Sorensen (1971) noted that there is conflicting evidence whether seaweed meals are more beneficial than standard mineral supplements and concluded that, as an animal food supplement, seaweeds have not shown any definite advantages over alternative additives.
95. Nevertheless, in the light of the present and prospective world food situation, the more widespread use of seaweed meals merits further attention. As indicated by Black as long ago as 1955, the substitution - and release for other uses - of cereals by seaweed meal in the basic feed rations may in certain instances by justifiable both economically and socially.
96. Perhaps the longest established, most widespread and most provenly effective use of seaweed is as a fertilizer. Wherever proximity to the coast has made access to the resource possible, seaweeds have been applied for many centuries to the land as a direct and simple manure. Since 1950 liquid seaweed products have enabled this practice to be extended, both geographically and in terms of specific uses.
97. The large brown algae, for example Macrocystis and Ascophyllum, are the principal species used for manure. Their value as a fertilizer derives not so much from their nitrogen, phosphorus and potassium contents but rather from their unusual properties as a soil conditioner and growth promoter. Seaweed fertilizer has been demonstrated to produce positive effects additional to those to be expected from their content of N, K and P.1 For example, seaweeds and liquid seaweed manures appear to promote resistance to plant diseases and plant pests, induce fruit setting and increase germination rates.
1 Myklestad (1964)
98. The coastal region of northwest France is a particularly striking example of the traditional use of seaweed as a manure. Along virtually the entire narrow coastal strip, the peasant farmers apply both drift-weed (“goémon épave”) and cut-weed (“goémon de dérive”) to grain crops, especially barley, potatoes, vegetables and vines, with highly beneficial results. The consistent use of seaweed manure is said to obviate any need for crop rotation. In some areas, notably Brittany, certain species of red seaweeds (known collectively as “maerl”) are collected, finely ground and are used because of their high calcium carbonate content instead of lime on acidy or peaty soils.
99. Transport problems of necessity restrict the use of seaweed as a direct, orthodox manure to areas upon or close to the coastline. However, with the introduction of liquid seaweed products, the use of seaweed as a fertilizer has become more widespread. The development of these products and the rapid growth in the U.K. of demand from the retail market in gardening aids, as well as from commercial horticulture and agriculture, was reviewed by Booth (1969) in a special lecture at the Sixth International Seaweed Symposium. Comprehensive data on the output of liquid seaweed fertilizers are not available but the U.K. is believed to be the major producer with an output (in the mid 1960s) estimated2 to be some 250 000 gallons per annum. Certainly this sector of the seaweed industry appears to have potential for further expansion.
2 Booth, E., In Firth (1969)