Konbu or edible kelp has been eaten in Japan since ancient times, packed full of essential minerals such as sodium, calcium, potassium and iodine it is particularly important to Japanese cookery being very rich in glutamine which imparts the savory taste of umami. In fact konbu contains a higher percentage of glutamic acid than any other food in the world.
Often referred to as the king of seaweeds, konbu is the only seaweed used to make dashi and therefore probably the single most important ingredient in Japanese cooking. By combining the glutamic acid in konbu with the inosinic acid in katsuobushi and the guanylic acid in dried shiitake a synergy of umami takes place, each acid bringing out the flavours of the other.
Most of the konbu produced in Japan is harvested in the northern island of Hokkaido, accounting for 90% of all production. The sea ice that drifts over to Hokkaido from Siberia is rich in minerals and provides an environment that produces the very best konbu.
Konbu is harvested towards the end of the summer, in the past it was often done by ama divers, diving down and cutting the konbu off near the base. Today, working in small boats, men and women cut the konbu free using razor sharp knives attached to long bamboo poles. As the konbu floats to the surface it is gathered with wooden rakes and pulled into the boats. Back on land, the konbu is laid out to dry slowly and naturally in the sun.
When harvesting the konbu the root is not removed or damaged. Only the higher leaf portion is taken so that the root of the konbu can regrow. It really is the ultimate renewable food source. There is a type of food called ne-kombu which uses the root and while nutritious and delicious, we do not supply it as it effectively kills the plant.
Wild konbu is subject to tight harvest restrictions to prevent overexploitation. The restrictions differ slightly from region to region but most konbu harvesting takes place for an average of 4 or 5 days a week, to a maximum of 25 days, between July and October.
The quality of konbu is mainly decided by the age. First year konbu is quite thin and therefore so is the taste. Konbu leaves naturally drop off after the first year and from the stump comes a new more superior tasting growth.
Much of the konbu on the international market is first year growth and the inferior quality is obvious when you make dashi with it. Second and third year konbu, while more expensive than the readily available first year konbu, has a substantial difference in taste, a far greater depth of flavour.
Types of Konbu
There are several different types of konbu each with their own unique characteristics.
Rishiri Konbu grown along the northern point of Hokkaido is considered to have the finest flavour and make the clearest dashi of all types of konbu. It is sweet, a little saltier than the others and quite hard. The hard leaves prevent it from discoloration or deterioration when simmered. It has dark brown leaves, is relatively thin and slightly wedge shaped near the stem. Rishiri konbu dashi is rich, savory, and clear and is traditionally favored by the Japanese master chefs of grand Kyoto kaiseki cuisine.
Rausu Konbu is highly prized and only grown in a very small area on the western most tip of Hokkaido’s main island. Due to the limited production it is sometimes unavailable for two or three months each year. The leaves are very wide and around 3 meters long. It is fragrant and soft, producing a unique rich tasting dashi. It is sub-divided by color into kurokuchi (black) and akakuchi (dark red) and the soft leaves impart a characteristically greenish-brown or reddish- brown colour to the dashi. Rausu konbu is mainly used to make dashi although it can also be processed into kobu-cha (konbu tea).
Ma Konbu produced in southern Hokkaido is the most widely harvested, most versatile and therefore the most commonly used of all the high quality konbu. Possessing light brown, thick wide leaves, ma konbu has a refined sweetness and produces a flavoursome, clear dashi. It is also good for further cooking and eating.
Hidaka Konbu, another good all-rounder for both making dashi and eating, as it softens quickly when simmered. It is blackish green in colour, longer and thinner than other konbu and produces a light greenish-yellow dashi. Because its edges are not as ruffled as the others it is often used for rolling or wrapping foods.
Kushiro (or Naga) Konbu is the longest and thinnest of all these premium konbu. Its leaves can grow up to 7 meters long and are grayish black in colour. It makes a bright, clear, robust tasting dashi and its semi-soft leaves are well suited to longer cooking or braising.
At Cook Tokyo we only stock premium grade konbu, harvested in the second or third year of growth.
Please view the items in our Cook Tokyo Shop for a more detailed explanation of each individual product.