Kombu – One of the pillars of Japanese cuisine
Kelp is a large species of seaweed. It is found in coastal areas all around the world, with a particularly large number of species in subarctic areas and the temperate zones of the northern hemisphere. Unlike many other plants, kelp reproduces by sperm and egg. The fertilized eggs grow into sporophytes large enough to be seen with the naked eye, which take over microscopic threadlike structures called gametophytes and eventually grow into large fronds.
Two species of kelp, Saccharina and Arthrothamnus, known as kombu by Japanese people, and have been a source of food for over 1,000 years. Worldwide, there are 22 varieties of kelp in these categories. 12 are found in Japan, and Hokkaido is the main fishing ground for all of them. The precursor to Hokkaido’s kombu came from the far east of Russia and was present when Hokkaido was formed around 20 million years ago. Since then, the kombu has spread to coastal areas throughout Hokkaido and diversified into the beloved varieties that Japanese people enjoy eating today, such as Naga-kombu, Mitsuishi-kombu, Ma-kombu and their regional variants (Hosome-kombu, Rishiri-kombu, Oni-kombu, etc.) Hokkaido is the only place in the world where these varieties grow, and Japanese cuisine in Japan and overseas alike owes its unique taste to Hokkaido kombu.
The hidden complexities of this iconic ingredient
Kombu from Hokkaido is eaten all over Japan. In addition to Tohoku, the region of the Japanese mainland that is closest to Hokkaido, kombu spread to the Hokuriku and San’in regions along the Sea of Japan coast in the 14th century and Osaka in the 17th century before eventually reaching the southernmost areas of Kyushu and Okinawa. These days, Japanese people can’t imagine Japanese cuisine without it. The list of dishes that contain kombu is endless, from national favorites such as tsukudani (kombu simmered in soy sauce and mirin), shio-kombu (strips of kombu that have been boiled with seasonings and then cut into small pieces) and kombu-maki (rolls of kombu cooked in a sweet and salty sauce), to unique local dishes in each region – kombu onigiri (rice balls) and kombu kamaboko (fish cakes wrapped in kombu) in Toyama, senmai-zuke (pickled slices of turnip seasoned with kombu) in Kyoto and Kubu-irichi (sautéed sliced kelp) in Okinawa. However, the most ubiquitous use of kombu in Japanese cuisine is for dashi, a broth that has been one of the core ingredients in Japanese cuisine since ancient times. While kombu appears in other countries’ cuisine too, Japan is the only country that has traditionally used it in a stock.
Visit a seafood market in Hokkaido and you’ll be amazed by the range of kombu products you’ll see. While each variety of Hokkaido kombu grows in specific areas, the environmental conditions vary a lot even within those areas, so the same variety of kombu can have totally different lengths and appearances depending on where it is caught. After so many centuries of eating kombu, Japanese people know exactly which kombu is best for each dish. The right kombu for traditional dishes is decided not only by variety but also by the place of origin and brand to get the flavorful just right. Kombu is graded according to the place of origin and then divided into specific classes. Even kombu from the exact same place can produce different-tasting dashi from year to year. It’s not dissimilar to wine in that regard.
Hokkaido’s thriving kombu industry
Over 95% of Japan’s kombu is caught in Hokkaido. Bringing in over 20 billion yen each year, kombu is one of the highest earners in Hokkaido’s fishing industry, surpassed only by scallops and salmon. Kelp is caught in summer, as the leaves grow significantly from spring to summer and begin to die when the waters turn cooler. Hokkaido has a long tradition of natural harvesting. Go to the beach early in the morning between July and October and you can watch crews piling the kombu they have caught into their boats or see kombu drying in the sun in the hoshiba (drying area). Those who use the traditional sun-drying method do not harvest kombu every day – since this method requires full sunlight, the kombu cannot be harvested on cloudy days, even if the sea is calm. (More and more areas are opting to dry their kombu by machine for this reason.) Traditional harvesters may wait for days or even weeks for proper weather conditions before taking their boat out for the next harvest.
Since natural kombu harvests vary in volume, Hokkaido’s kombu industry supplements its natural kombu with artificially grown kombu to ensure a steady supply and boost the volume of kombu for export. Ma-kombu, Rishiri-kombu and Oni-kombu are grown artificially in Hakodate in southern Hokkaido, Rishiri and Rebun Islands in northern Hokkaido and Rausu in eastern Hokkaido respectively. You can see planting buoys floating in the sea around these areas. As the varieties of kelp that are grown artificially only live for two years, artificial planting takes place in two-year cycles to get the best leaves, except in Hakodate where kombu leaves reach their best condition after just one year. Young kombu begins its life in an indoor facility with the optimum conditions to achieve as much growth as possible in a short space of time. It is then transferred to the sea to grow over a one- to two-year period. In southern Hokkaido, the kombu is ready for harvest after just one year, while two years are required in northern and eastern Hokkaido as the sea reaches freezing temperatures and receives less sunlight. In Rausu, the process is complicated further by the drift ice that covers the Sea of Okhotsk – the kombu growers handle this by moving their kombu growing facilities under the ice.
More than just a great taste
The delicious umami taste of kombu stock comes from an abundance of amino acids such as glutamic acid and aspartic acid. As the biggest producer of kombu, Hokkaido has no shortage of Japanese restaurants where you can enjoy the subtle nuances of that great taste. In recent years, its irresistible appeal has attracted foodies from all over Japan and even overseas. While products made from different varieties of kombu grown in Europe and North America have become popular worldwide via the Internet, they cannot take the place of authentic Hokkaido kombu. When it comes to traditional Japanese foods like dashi dishes, there’s really no substitute for the kombu from Hokkaido that Japanese people have enjoyed for years.
And the taste is only half of the story. Kombu is also attracting attention for its incredible health benefits. It is rich in fiber, one of the six most important nutrients that the body needs. The fiber found in kombu includes a soluble fiber called fucoidan and a binding agent called alginic acid, which maintain the right conditions in the intestines and prevent lifestyle-related diseases – for example, alginic acid is said to be effective in preventing high blood pressure and lipids in the blood, while fucoidan prevents blood clots and hardening of the arteries. Kombu also absorbs an abundance of minerals from the sea, which play a vital role in building tissue and maintaining general health. In addition to the main minerals the body needs, kombu contains a variety of valuable trace minerals – your body will thank you!
Supporting marine ecosystems and fishing industries alike
Hokkaido’s diverse kombu forms large colonies along coastlines all around Hokkaido, creating an underwater forest. Just like a forest on land, it is a valuable home for a variety of species, which feed, spawn, care for their young, hide from predators and sleep there. Of course, the marine life it attracts also makes it a prime fishing ground. It also performs photosynthesis like other plants, converting carbon dioxide into oxygen, sugars and carbohydrates in the sea. This plays an important role in reducing carbon dioxide in the atmosphere in the areas where kombu grows. Sadly, the increasingly rapid environmental changes that have taken place in recent years have resulted in shrinking of Hokkaido’s kombu colonies and changes in the areas where they grow. Conservation efforts must not just protect the kombu itself but preserve the biodiversity and environment of these areas as well. The implications here are not just environmental but cultural too – the survival of Japanese food culture as we know it depends on protecting these underwater forests. Currently, there are multiple initiatives underway throughout Hokkaido in the conservation of kombu colonies.
With the naming of Japanese cuisine as an Intangible Cultural Heritage by UNESCO increasing its renown worldwide, the importance of kombu has also become increasingly known thanks to coverage on TV and in books. However, there’s no substitute for taking the time to travel to Hokkaido to experience kombu on its home turf. Doing so will help you to gain a whole new appreciation for the diversity, history and complexity of this staple element of Japanese food culture.
I conduct research on the biodiversity of the kelp that grows in Hokkaido and other coastal areas in the North Pacific. I also study conservation and breeding methods.
Hakodate Morning Market
Marvel at the incredible range of kombu products and buy some to enjoy for yourself
Learn all about what kombu means to the Japanese people from a variety of exhibits. You can even watch exciting videos of kombu growing under the sea and harvested by a crew.
Shin Hidaka Town Museum
Find out more about how local kombu is harvested and exported.
Erimo Town Community Museum Horoizumi and Fisheries Center
Learn all about kombu by seeing real kombu up close!