The Umami Ingredients That Enhance Japanese Cuisine

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.

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.

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.

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.

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.

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.