Kombu belongs to the brown-algae family and is harvested on the coasts of Hokkaido, the northern island of the archipelago and in Tohoku, the north-eastern part of the main island of Honshu. There are various species of algae and among them, those most commonly used for dashi (Japanese stock) are makombu, rishiri-kombu, and rausu-kombu. Hidaka-kombu is simmered with seasonings to be used as side dishes such as simmered kombu and takiawase. Kombu for dashi is grown for two years and harvested from July through September. In addition to the area of harvesting, factors such as the shape of the frond and its degree of luster are used to give each piece of kombu a rating from one to six.
Ingredients for Dashi Kombu Ingredients for Dashi KombuUmami Information Center
Major kombu varieties Major kombu varietiesUmami Information Center
Japan Kombu Map Japan Kombu MapUmami Information Center
How is kombu made?
As with dashi made from other ingredients, the time it takes to make kombu dashi is short, while the dried kombu making process is rigorous and time consuming. Kombu thrives in the cold waters off Hokkaido in the north of Japan, tending to inhabit waters around five to eight meters deep and generally takes around two years to reach the level of maturity required for harvesting. Harvesting usually only takes place during the summer months of July to September, on dates determined annually, and is traditionally carried out by kombu harvesters in boats.They use long wooden poles with hooks attached to detach the kombu from the seabed at the root.
As soon as the kombu reaches dry land, it is laid out on rocks to dry. On a summer day, this process can be completed in four or five hours. Once dry, the kombu is taken indoors, the shape of each frond is adjusted and then it is dispatched. Alternatively some kombu undergoes a further maturation process known as kuragakoi (cellar conservation). This process improves the flavor of the kombu and removes its distinctive seaweed odor.
KombuUmami Information Center
Dried kombu is abundant in the umami substance glutamate.
various kombu&main amino acids in kombu dash (left in water for15mins) various kombu&main amino acids in kombu dash (left in water for15mins)Umami Information Center
What makes dashi so delicious?
Kombu used to be shipped with great care from far off Hokkaido to Kyoto, the ancient capital of Japan that flourished for nearly a thousand years. In the Heian period (794-1185), shojin ryori, a type of vegetarian cooking, was introduced from along with the teaching of Buddhism warning against the taking of life. The ingredients used in shojin ryori consist entirely of vegetables and soybean products – meat, fish, or seafood are never used. Kombu dashi is indispensable for enhancing the taste of the vegetables used in shojin ryori. The dashi used in Japanese cuisine is very easy to make. Have you ever tasted a kombu dashi in its purest form? If you haven’t, cut a piece of kombu, put it in a cup, and add water. Let it sit for about 20 minutes. Dashi will begin oozing out from kombu in a few minutes – try it and a light, subtle taste will fill your mouth. What makes the dashi so indescribably delicious is the umami. The main umami substance in kombu dashi are glutamate and aspartate.
Katsuo-bushi (dried bonito flakes)
Katsuobushi is made of katsuo or bonito, skipjack tuna, a saltwater fish. Bonito Skipjack tuna are high in protein and unprocessed, they have a 25% protein content and as katsuobushi, the figure rises to 77%. They are also rich in inosinate, a key umami substance; the umami is multiplied many times over when combined with glutamate. This is the mechanism behind ichibandashi (first soup stock) in Japanese cuisine. Katsuobushi is not just about smoking the fish; the creation process is a tradition that has been handed down over nearly 400 years. Making katsuobushi involves drying katsuo, introducing beneficial mold that triggers fermentation, and creating a deeper, richer flavor. The process takes many months, and the end result is a surprisingly hard, richly flavorful food product. The finished katsuobushi is shaved using a grater box. The resulting flakes are used mainly for making dashi (stock). This method can use other fish such as tuna, mackerel, and sardine.
Ingredients for Dashi Katsuobushi Ingredients for Dashi KatsuobushiUmami Information Center
The making of katsuobushi
The process of making katsuobushi begins with filleting of fresh bonito skipjack tuna into three pieces, referred to as kame bushi (turtle block). The large piece is then further split along its length into two halves — called mebushi (belly) and obushi (back) — that make up the honbushi (main block). The blocks are placed in a woven tray in hot water, carefully arranged to ensure uniform flavor in the end product, and simmered for 60 to 90 minutes in a step known as shajuku, sealing in the inosinate. The skin and bones are then removed. The blocks are called namaribushi at this point.The next step is baikan (“smoke-drying”). The namaribushi undergo lengthy smoking to remove water content and prevent spoilage. After the first round of baikan, the cracks and cavities are repaired using a paste made from the head and nakaochi (tuna scrape), followed by over a dozen more rounds of baikan to remove even more water, kill harmful bacteria and prevent them from taking hold, and block oxidation. The process of baikan transforms the namaribushi into arabushi.
Honkarebushi, a higher grade of katsuobushi, is made by putting the arabushi through a process known as kabitsuke (mold application). A coating of beneficial mold seals in aroma. The spores draw out the last of the moisture from deep inside the block; they also break down triglycerides, giving clarity to any soup stock eventually made from that honkarebushi. Around two weeks later, the block is temporarily removed from its tub, sun-dried, and individually dusted to remove the surface mold. These steps are repeated for around four months. It is through this long drying process that katsuobushi, known as the hardest food in the world, is created.
Katsuobushi and inosinate
Katsuobushi contains extremely high levels of the umami substance inosinate. In fact, the process of baikan and kabitsuke boosts the inosinate level over what is found in fresh bonitoskipjack tuna. Shaving katsuobushi with the grater box increases surface area and makes it easer to prepare stock. The paper-thin shavings also allow inosinate, which dissolves easily in water, to be quickly extracted while preventing other, less dissolvable amino acids from releasing their flavor or clouding the stock.
Katsuobushi and dashi
Katsuobushi is shaved using a grater box before being used to prepare stock. The simple, rich dashi made from unfermented arabushi is also a popular part of Kansai cuisine. The obushi (back) of honkarebushi produces refined stock low in fat, while the mebushi (belly) yields a dashi with more richness. Ichibandashi (first stock) made from a combination of glutamine-rich kelp and inosinate-rich katsuobushi represents a cooking method that makes the most effective use of umami synergy. This is why ichibandashi is the bedrock of Japanese cuisine. High-end establishments such as a ryōtei will also use magurobushi (bluefin tuna) at times instead of katsuobushi, for a dashi with a refined and clean flavor.
The effects of umami in dashi
Ichiban dashi (first brewed) is made by adding lots of katsuobushi to kombu dashi when it comes to a boil. Ichiban dashi is then strained with a strainer covered with thin cloth on top. Although katsuobushi is added to kombu dashi for only a few seconds, the umami taste of ichiban dashi is more pronounced than that of kombu dashi. The fragrance of katsuobushi then increases. Inosinate is a key substance in the umami taste of katsuobushi. Moreover the umami taste of dashi is greatly enhanced when the glutamate found in kombu meets the inosinate of katsuobushi. Adding katsuobushi to kombu certainly has a wonderful synergic effect.
umami substance and intensity in kombu dashi & ichiban dashi umami substance and intensity in kombu dashi & ichiban dashiUmami Information Center