Kelp (コンブ)

Kelp is a kind of seaweed belonging to the Division Heterokontophyta, Class Phaeophyceae, Order Laminariales, Family Laminariaceae.

Kelp is called "Konbu" in Japanese, mainly written as "昆布" or "こんぶ" when kelp is recognized as foodstuffs. In the biological area, the character 'コンブ' (which is pronounced "Konbu") is used as the Japanese name of "kelp," but to be exact, 'konbu' is not a species existing on the earth. As shown in "Ma-konbu" (Laminaria [hereafter, L.] japonica), "Rishiri-konbu" (L. ochotensis) and "Mitsuishi-konbu" (L. angustata), the species name is used as a standard Japanese name for kelp.

Ecology

Family Laminariaceae has lots of genera, including the genus Laminaria to which L. japonica belongs, and the genus Kjellmaniella gyrata to which Kjellmaniella crassifolia belongs. In addition, there are closely related genera belonging to the same Order Laminariales, such as the genus Alaria praelonga to which wakame seaweed and others belong, and Chordaceae which is believed to be retaining traces of the primitive appearance of kelp.

Kelp is growing mainly along the coast of Hokkaido, as well as on the Sanriku Coast. Generally, the plant belonging to the Family Laminariaceae is the typical seaweed growing in the cold Oyashio current (the Kuril current), while some of them, such as Eisenia bicyclis and Ecklonia cava, grow in the warm ocean. Not only kelp is edible seaweed, but also it is useful to preserve various ecosystem by forming a vast scale of algal bed.

Kelp multiplies by spores.
Having the capability of moving in the sea by using two flagellums, the spore of kelp (the size is about five micrometers) is especially called 'zoospore.'
Released from the surface of kelp, the zoospore clings to the rock in the sea and others.
The clung zoospore germinates to become a microscopic organism called 'gametophyte.'
One zoospore is transformed into one gametophyte, which is provided with either the male feature or the female feature. Ovum is produced in the female gametophyte, while spermatozoon is produced in the male gametophyte. When the ovum is fertilized by the spermatozoon, a fertilized egg is produced and grows up. The grown-up fertilized egg becomes a visible 'sporophyte,' namely the familiar seaweed "kelp" which we usually see.

Fishery

About 120,000 tons of kelp was produced in Japan in 2005 (the weight was measured in raw condition). Cultivated kelp accounted for about 35% of the whole production of kelp in 2005. Hokkaido accounts for more than 95 percent of the production of natural kelp. Moreover, about 800,000 tons of kelp is cultivated in China.

The coast of Hakodate City, Hokkaido is a great place for cultivating L. japonica. L. japonica is also cultivated in Iwate Prefecture, Miyagi Prefecture, and the Seto Inland Sea and so on these days. L. japonica is biennial seaweed, requesting a great deal of time extending as long as two years and labor in order to be cultivated. Therefore, a forcing culture method has been deployed to produce L. japonica with high quality similar to biennial-typed L. japonica in a year. Moreover, the cultivate method for L. angustata, L. ochotensis and Laminaria diabolica has been established, which are recognized as important species from the industrial viewpoint. As for other species, the cultivate method is not established, because they can grow naturally in plenty, or they are less useful than the species mentioned above. However, the cultivation of Kjellmaniella crassifolia has started, because its value has gradually been recognized in recent years.

Kelp is gathered in by being wrenched off with a pole thrust at the roots of the kelp by a fisherman on a small boat. Collecting kelp washed up on the shore and hauling kelp rushing for the shore on the beach with a hook are other methods to gather kelp. Then, brought to a drying ground covered with pebbles, the gathered kelp is spread for drying. Turned over once or twice, kelp is dried evenly. Kelp should be dried in moderation, because it becomes easy to break when being dried too much. It needs half a day to be dried. If it is exposed to the rain while being dried, its commodity value would become null. Therefore, fishermen sometimes put off going fishing when the weather forecast predicts rain at a high rate. A drying machine is also introduced in drying process, but machine-dried kelp is inferior to sun-dried kelp in quality. However, some regions are forced to use such a drying machine frequently due to a dense fog, the lack of sunshine and so on. As the drying process must be finished within a short period of time, part-time workers to engage in the drying process are often recruited. It is not uncommon that a simple lodging house is set up near a fishing spot to stay.

Production areas and species

Hokkaido is the main production area of kelp. Particularly, L. japonica, L. diabolica, L. ochotensis, L. angustata and L. longissima, coming in order of quality, are famous.

Laminaria japonica (called "Ma-konbu" in Japan)

L. japonica is known as kelp produced in the south part of Hokkaido, mainly from Tsugaru Straits to the coast of Funka Bay. L. japonica has quite a lot of brands and rankings.
L. japonica produced on the coast of former Minamikayabe-cho Town (present Hakodate City) is recognized as the top quality products, called by the brand name 'Shirokuchihama.'
In addition, L. japonica produced on the coast of former Esan-cho Town is called 'Kurokuchihama,' that produced in the Tsugaru Straits is called 'Honbaori' and that produced in other sea areas is called 'Bachigaiori.'
Market value is also in the same order. There are also several rankings within a brand according to the quality. Soup stock made from L. japonica has a delicate flavor with a transparent appearance, as well as characteristic sweetness. In Osaka, people prefer this taste so much that they usually use L. japonica for making soup stock. Moreover, L. japonica is shaven to produce processed goods, shredded tangle, such as "oboro-konbu" and "shiraga-konbu."

Laminaria diabolica (called "Oni-konbu" or "Rausu-konbu"in Japan)

L. diabolica ranks as the top quality products along with L. japonica. Having thick taste, L. diabolica is preferred to be used for soup stock by the people living in Kanto region. The soup stock made from L. diabolica has a dark brown color, with a little egumi (bitter and astringent tastes) peculiar to kelp. Toyama Prefecture in the Hokuriku region is one of the major consuming areas.

Laminaria ochotensis (called "Rishiri-konbu" in Japan)

L. ochotensis also ranks as the high quality products, coming after L. japonica and L. diabolica. The soup stock made from L. ochotensis is a little bland compared to that made from L. japonica or L. diabolica, however, it has a delicate flavor with a clear appearance as well as a little salty taste. Therefore, L. ochotensis comes in useful when cooking Kaiseki ryori (a simple meal served before a ceremonial tea). In particular, it is essential for Kyo-ryori (local cuisine of Kyoto). L. ochotensis is the most common kelp for making soup stock in Kyoto, regarded as the high quality kelp.

Laminaria religiosa (called "Hosome-konbu" in Japan)

L. religiosa is kelp produced on the Sea of Japan coast such as the areas ranging from Matsumae to Rumoi. Unlike other kelp, L. religiosa is annual, therefore, it is gathered after one year. Because a cross section of L. religiosa is whiter than any other kelp, it is often processed to produce shredded tangle, such as "oboro-konbu" and "tororo-konbu." The fact that the distribution range of the above-mentioned four species are continuous, as well as the genetic distances among them are quite short, makes interspecific hybridization possible. It is thought that enough differentiation, by which kelp would be further classified into species, has not yet occurred.

Laminaria angustata (called "Hidaka-konbu" or "Mitsuishi-konbu" in Japan)

L. angustata is produced on the Pacific coast of the Hidaka region. As L. angustata cooks tender quickly, it is suitable for such dishes as kobu maki (a kelp roll), tsukudani (konbu boiled in sweetened soy sauce) and oden (a Japanese pot-au-feu) in which people can eat kelp itself. It is also used to make soup stock in places such as the Kanto region and private households where people are less particular about soup stock made from kelp. However, soup stock made from L. angustata is cloudy and pale, therefore restaurants in the Kansai region rarely use L. angustata for making soup stock.

Laminaria longissima longissima (called "Naga-konbu" or "Hamanaka-konbu" in Japan)

The Pacific coast around Kushiro City produces large amounts of L. longissima. The length reaches as long as 15m. While boasting the largest production among kelp, L. longissima is regarded as kelp for general use and sold at a low price, because it contains a little umami (a kind of flavor) ingredient. However, L. longissima has been used frequently instead of vegetables in Okinawa areas since long ago, having become the most popular kelp there. Like L. angustata, L. longissima is soft, therefore it is generally used to make kobu maki. In addition, it is cut up into pieces and eaten as a salad without being heated, or fried with pork which goes with the kelp. The short genetic distance between L. longissima and L. angustata supports the theory that L. longissima is the variety of L. angustata.

Kjellmaniella crassifolia (called "Gagome-konbu "or "Gagome", literally woven-bamboo pattern in Japan)

The name of Gagome is derived from the concave and convex Ryumon (龍紋) patterns on the surface of its frond (to put it more precisely, it means thallus), which is likened to the stitch of woven basket. It grows in the area from the Tsugaru Straits through the coasts of Kameda Peninsula (former Minamikayabe-cho Town) of Hakodate City to Muroran city (except the Funka Bay) in Hokkaido, on the coasts from Minmaya to Iwaya, Aomori Prefecture, on the coasts of Omoe, Miyako City, Iwate Prefecture, the southwestern Sakhalin, Enkai shu ([Russian] maritime provinces) and the northeastern part of the Korean peninsula. It is normally found at the depth of 10 to 25m below the surface of the sea. As Kjellmaniella crassifolia which grows in shallow waters coexists with L. japonica, it used to be classified into coarse seaweed. It grows up to 2m in length and it is believed to have a lifespan of three to five years. Its commodity value was low because it was not used for making soup stock. However, the discovery of the fact that Kjellmaniella crassifolia contains more viscous polysaccharides called 'Fucoidan' than other kelp, as well as the fact that such Fucoidan may work as a functional ingredient, raised the price sharply. Kjellmaniella crassifolia grown naturally had mainly been gathered until now. However, its production dropped to 10 % compared with that in its best period. The establishment of the cultivation technology is also expected to meet public growing demand.

The main ports of landing

Fiscal year 2002

The first place

Ofune Port (Hokkaido)

The second place

Chirippu Port (Hokkaido)

The third place

Kesennuma Port (Miyagi Prefecture)

The fourth place

Akkeshi Port (Hokkaido)

The fifth place

Osappe Port (Hokkaido)

Usage as foodstuffs

After being dried, kelp is widely used for making soup stock in Japanese cuisine. It is said that the Russians, who regard kelp as 'Garbage of the sea,' cannot understand why the Japanese willingly eat kelp. Kelp is also used to produce shredded tangle, such as "oboro-konbu" and "tororo-konbu." Kelp is used for making processed foods like su-konbu (a sour Japanese snack made of kelp) and oshaburi-konbu (a chewing-gum-typed kelp), which have been counted among foods served with tea or refreshments in recent years. There is a custom in Hokkaido of eating parboiled young kelp as sashimi. Hayanie-konbu (Quick-cooking kelp) sold commercially is made from Saomae-konbu kelp, L. angustata and L. japonica. Young and thin frond of them are chosen, and dried after being boiled.

According to the Family Income and Expenditure Survey reported by the Statistics Bureau, Ministry of Internal Affairs and Communications, Aomori City, Morioka City, and Toyama City are the largest consumers of kelp (which is calculated by taking an average of three years since 2003 per household). They consume kelp 1.4 to 1.8 times as much as other cities in Japan on average. Naha City, Okinawa Prefecture is 7th place, consuming 1.1 times the national average. As Okinawa Prefecture used to be a relay exchange point to export kelp produced in Japan to China, a food culture of using kelp for cooking was produced, which resulted in high kelp consumption. However, kelp consumption has been decreasing in recent years because more young Japanese are moving away from traditional food these days. Fukui City, Otsu City and Toyama City boast high consumption of tsukudani made from kelp, followed by cities in the Kinki region such as Kyoto City and Nara City. Thanks to kitamae-bune (cargo ships that sailed the Japan Sea during the Edo period), a large amount of kelp had been in circulation since long ago in the Kinki region. People in the Kinki region consume a lot of tsukudani as they have a specific kelp consumption culture and the processing technology unique to the region.

Kelp is recognized as a food good for health. Especially, due to abundant dietary fiber, iron, calcium, etc. contained in kelp, it is popular as a health food. Kikunae IKEDA discovered in 1908 that the main constituent of umami extracted from kelp, which had been used for cooking from old times, was glutamic acid. Based on this discovery, umami-chomiryo (chemical seasoning) AJI-NO-MOTO seasoning was made.
Kelp also contains a large quantity of iodine, one of the essential elements for human beings
However, we should be cautious not to take kelp too much, because excessive iodine may cause the functional disorder of thyroid.

History

It is believed that kelp was brought into Kyoto by the Hosokawa family of Minamoto clan, which was included among Sankanrei (three families in the post of kanrei, or shogunal deputy), using vessels of Suigun (warriors battle in the sea) which had been pirates. Shoku Nihongi (Chronicle of Japan Continued) is the first historical document in Japan with a description of kelp. According to Shoku Nihongi, kelp was dedicated to Imperial court and Shogun family as a tribute from Tohoku region in those days. Therefore, kelp was shipped to important ports in Osaka via Sakata Port situated on the coast of Japan Sea, later via Shimonoseki Port.

Furthermore, with the extensive development of Ezo (present Hokkaido) in the Edo period, kelp was spread to the whole country because the sea route was fully provided and the shipping volume increased. Particularly, kelp was a main product to be dedicated to the Chinese dynasty in the Ryukyu Kingdom period. People living in the Ryukyu Kingdom (present Okinawa Prefecture) had no choice but to find ingenious ways to consume the fragments of kelp or lower class kelp personally that were regarded as unsuitable for a tribute. As a result, kelp became an ingredient frequently used in Okinawan cuisine later recognized as a traditional food.

Kelp in the food culture of Kamigata (Kyoto and Osaka area)

When dried kelp is left in a warehouse in humid Osaka, the astringency of the kelp is removed, instead, the sweetness increases because kelp matures. Kelp spread to Osaka only after commercial ships started to carry kelp to Osaka taking the Japan Sea route by way of Shimonoseki. A humid climate of Osaka, a major collection center of agricultural products and dry foods in the Azuchi Momoyama Period, accomplished maturity of the flavor of dry foods and kelp.
Therefore, in the Edo period, foods with a taste peculiar to the soup stock made from L. japonica became so famous as to be ridiculed by saying 'In Osaka, they spend all their money on food.'

Dry foods shipped from Ezo in exchange for agricultural products of Osaka included Yesso scallop, Pacific cod and dried herring, in addition to kelp. Commercial ships mainly took the Japan Sea route to avoid the route in the Pacific Ocean. As a result, Tsuruga and Obama consumed more kelp than Osaka.

In Osaka, a craftsman in Sakai City, a town of cutting tools, created the shredded tangle by shaving the surface of sweet vinegar-soaked dried kelp. The black part of the surface layer of kelp becomes 'oboro-konbu' (black oboro) with a strong sour taste because this part contains plenty of sweet vinegar. After the surface layer is shaved, white part of the inner layer comes out. This white part retains its natural sweetness because it is not soaked in the vinegar. The shredded tangle produced from this part is called 'taihaku oboro' (literally, thick and white shredded tangle). The core of the kelp left behind is used as battera kelp (tangle used for mackerel sushi, also called shiroita-konbu) for cooking battera sushi (mackerel sushi) and Oshi-zushi (lightly-pressed piece of sushi topped with cooked ingredients). It is believed that only craftsmen with excellent technique can shave kelp thinly.

In above-mentioned Sakai City, 'Oboro-konbu' also became popular. In addition, in Tsuruga, a collection center of kitamae-bune, the technology to produce 'oboro-konbu' developed. The edge of kelp, remained after the body part was eliminated for making shredded tangle, is called "tsume-konbu" (nail-like pieces of tangle), sometimes eaten as a snack. As for other processed foods made from kelp, shio-konbu (L. angustata boiled in brine and soy) is famous. It seems that shio-konbu boiled with soy sauce was cooked using L. religiosa in the Sengoku period (period of warring states), which was served in the ceremony to go into a battle as lucky foods along with dried chestnuts, because the sound of konbu (kelp) made people think of joy (joy is "yoro-kobu" in Japanese, "yoro-kobu" and "yoro-konbu" have similar sounds) and dried chestnuts made them think of victory (dried chestnuts are called "kachi-guri" [literally, victory and chestnut] in Japanese).

The name 'shiofuki-konbu' was applied to the processed foods made from shio-konbu boiled with soy sauce, which received the procedures as follows: Drying on the hibachi (brazier) using a wire grill for three times while dipping in soy sauce each time after drying. The surface may look powdery. This powder like material is the crystallized umami constituents. Seasonings like inosinic acid and glutamine component extracted from kelp are often sprinkled these days.

Use in the field of fermented foods

Fermented salty kelp was invented recently as part of fermented food. A substance equipped with a sulfate radical is originally contained in kelp, which prevents the growth of bacteria. However, bacteria were found in the benthic feeder, which had the capability to ferment kelp without being influenced by the sulfate radical contained in kelp. This discovery accelerated the development of the fermented salty kelp. TAKARA HOLDINGS INC., Kyowa Hakko Kirin Co., Ltd. and Kohara Honten Corporation have their own original technology for fermenting kelp.

Kohara Honten Corporation is a pioneer in the ferment technology of kelp, which developed a new fermented food called 'Maikon,' shio-konbu fostered by wild yeasts. Suntory Holdings Limited also succeeded in producing a health food made from fermented kelp on a commercial basis, using the technology relating to the lactobacillus developed by Dr.Tsunataro KISHIDA. It is reported that the fermented kelp can lower the blood-cholesterol levels.

Use in the medical field

Dried kelp has the property of swelling when it absorbs moisture. For this property, kelp is used as a raw material to produce the medical dilator. Laminaria is the medical dilator produced from kelp, which is used to dilate the uterus and other organs. As raw materials, stalks and roots of L. diabolica (called Rausu-konbu in Japan, a scientific name Laminaria diabolica Miyabe) are mainly used.