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Some 100 000 tons (product weight) of edible seaweed preparations are eaten annually in Japan, the three main products being nori, kombu and wakame.

Nori is a collective name applied to various edible products derived from the purple laver, Porphyra, and certain other algae. Originally, only naturally-occurring Porphyra was used as the raw material but, with increasing demand, attention turned to its cultivation.1 Porphyra and other species are now the basis of a very substantial cultural industry in many parts of Japan, but in particular along the shores of Tokyo Bay in the prefecture of Chiba and the coastal area of the Seto inland sea. Natural supplies of nori, whose major source is the northern island of Hokkaido, now account for only a very small fraction of total production. In recent years the output of cultivated nori has increased extremely rapidly, from some 65 000 tons (wet weight) in 1958 to around 140 000 tons per annum during the 1960s and to over 300 000 tons annually in both 1973 and 1974,2 with a value of some U.S.$ 450 million in 1973.

1 Tanikawa, 1971

2 See Table IX of main text

Only small quantities of nori are eaten fresh and generally the weed is dried, either naturally or in special chambers, before sale. After harvesting, which is undertaken from November/December to April, the raw weed is washed, pounded and rewashed to remove impurities; once drained, the fronds are chopped into fine pieces, mixed with fresh water and then spread on bamboo mats of uniform size and dried. When dried (to about 16 percent moisture) the sheets of nori are pressed flat into bundles which are usually marketed in airtight containers, the product being hygroscopic. Nori produced from cultivated Porphyra is normally known as “Asakusa-nori”, after the then village of Asakusa (now a suburb of Tokyo), once renowned for the culture and preparation of nori; when derived from naturally grown algae the product is usually described as “ama-nori”.3 The term “hoshi-nori” is also found in the literature and appears to refer to dried nori products in general. Nori prepared from the large green seaweed Enteramorphya4 and the brown seaweed Monostroma are known as “ao nori” (Levring, Hoppe and Schmid, 1969).

3 M. Hotta, personal communication

4 Products from this weed are also sometimes known as “Awo-nori”

Nori is a very versatile ingredient in a variety of Japanese dishes. It is used to wrap round the popular dish “sushi”, in which vinegared rice, vegetables and fish are rolled in a sheet of nori which is then sliced into small individual servings. After toasting over a charcoal fire, nori is widely used in small broken pieces as a flavouring additive to soups, sauces and broths, or is eaten with boiled rice after a preliminary soaking in soybean sauce. Nori is also employed in the manufacture of crackers and biscuits and is eaten in a variety of roasted and seasoned preparations. Domestically-produced supplies of nori are supplemented by controlled imports, amounting to several hundred million sheets annually, from the Republic of Korea.

Another very important edible seaweed product is kombu5 prepared from various species of the brown seaweed Laminaria, or kelp. After harvesting the Laminaria is carefully dried, the stipes and root discs removed and the fronds sorted into qualities for shipping in bundles to the kombu factories. In Japan the main resources of the raw material are found in the northern islands of Hokkaido; the production of kombu itself, however, is centred in Osaka, southwest of Tokyo.

5 A more accurate anglicized representation of the Japanese word is “konbu”

Many types of kombu are prepared, perhaps the commonest being green or shredded products (“Ao-kombu” or “Kizami-kombu”). In this process the dried algae are boiled, with a solution of green aniline dye, and stirred for up to half an hour; the fronds are then, after having been hung in the air to dry, compressed in frames and bundled into piles weighing approximately 100 kg each. The bundles are next cut into smaller units which are again compressed, a little water having been added. Finally, the blocks are sliced and shredded and, after the surfaces of the shreds have been allowed to dry, are packaged in paper or boxes. Fronds of the thicker species of Laminaria are soaked in diluted vinegar to prepare black-kombu (“Kuro-tororo”); a white product, known as “Shiro-tororo”, can be obtained by scraping away the surface of black-kombu. Among other varieties are seasoned, powdered, roasted and sugared products and one sold in the form of filmy sheets.

Depending upon its product form, kombu is used as soup stock, boiled as a vegetable, is soaked in soy sauce and served as a seasoning for rice dishes or, in dried strips, eaten as a snack food.1 In contrast to most other Japanese edible seaweed products, the demand for kombu appears to be falling.2 In the years prior to the second world war, Japan's output of Laminaria was between 300 000 and 500 000 tons (wet) per annum; over the last ten years output has ranged from 110 000 and 170 000 tons, on a declining trend.

1 Hunter, 1975

2 The market still, however, remains substantial, being valued at some U.S.$ 150 million in 1973

Considerable quantities of Laminaria were once used by the Japanese iodine industry; this is no longer the case but this loss of a market probably does not account for the whole of the fall in output. In recent years kombu may have become less popular because of the extremely rapid rise in its market price, a consequence, perhaps, of the relatively labour-intensive methods required in its preparation; in any event, per caput consumption appears to have fallen by about 15 percent over the last decade, whilst that of wakame and nori has nearly doubled.

A contributory factor may be increasing costs of harvesting the natural resources of Laminaria. Compared with Porphyra and Undaria, the weeds used in the preparation of nori and wakame, supplies of cultured Laminaria have so far been very limited. Whilst Chapman (1970) notes that the Japanese have practised the cultivation of Laminaria species for some 300 years, the total commercial output of cultivated Laminaria appears to have been rather small.3

3 The Ministry of Agriculture and Forestry, Tokyo, in its Annual Statistical Reports records the output of cultivated Laminaria as 3 300 tons in 1972 and 7 600 tons in 1973; earlier recorded output was a few hundred tons per annum

Japanese consumption of a third edible seaweed product, wakame, eaten in soybean soup since ancient times, has risen particularly rapidly during the last decade. Supplies of the raw materials, the large brown seaweed Undaria pinnatifida,4 have been very considerably boosted since the mid 1950s by cultured production which now accounts for over 80 percent of total output, valued at approximately U.S.$ 100 million in 1973.

4 The species Alaria is also occasionally used to prepare wakame, but the product is regarded as being of inferior quality

The treatment of the raw weed is basically simple, requiring washing and drying only. Tanikawa (1971) distinguishes between two main wakame products, one desalted, the other with the salts retained. The latter is now produced in small quantities only and the principal product marketed is a desalted type, “Naruto-wakame”, named after a district near Kobe. This preparation involves the coating of the Undaria with burned ash before a preliminary partial drying on straw mats. The mid-ribs of the plants are then torn off and the fronds, having been washed clean of ash, are hung from rope lines for a further drying. After removing inferior fronds, the process is completed with a final period of drying on straw mats. The wakame is folded into lengths of about 30 cm and sold in cellophane bags or paper boxes. In another process the wakame is desalted by means of boiling water. Wakame is also1 marketed in the form of short, cut-up chips (“Kizami-wakame”) and as a roasted, sugar candied product, sometimes in tins. Among a variety of other forms is “Ita-wakame”,2 in which the mid-ribs of the weed are not removed; this product is crushed by hand and sprinkled upon rice dishes.

1 Chapman (1970)

2 Tanikawa (1971)

A variety of other seaweeds are used for human consumption in Japan, often being prepared domestically as jellies, condiments, soup additives or salads. Among a large number of such preparations are “Hijiki”, derived from the tender brown seaweed Hizikia fusiforme and consumed fresh or dried as a vegetable, “Arame” (Eisenia bicyclis), “Hondawara” (the young plants of Sargassum spp.) and “Miru”, prepared from green seaweeds of the Codium genus, all of which are used as a soup ingredient or eaten with soy sauce.

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