Ma kombu (Yamadashi) from Donan

Just like great wines, kombu quality depends on harvesting area, active sea currents in the growing area, relief and rivers near beaches and their alluvial deposits, exposure to the sun... Kombu sought by Okui must be harvested at perfect maturity, from July to September, after at least two years of growth. Seaweed then reaches a length of 2.5 to 3 meters and even 10 meters for the most exceptional specimens. Kombu seaweeds are dried exclusively in the sun until they have a nice dark bronze to black exterior color, while preserving a light interior color.

OKUI KAISEIDO kombu:

Rishiri & Rebun Kombu
Rishiri & Rebun kombu are the kings of kombu and the most expensive in Japan. They are known to have a tough fiber and it is usually difficult to extract the umami. Slowly heated to 60℃ they produce a very clean and rich dashi with a golden color. They are essential ingredients in Kaiseki and Shojin cuisines and are known for their mild flavor.

Rausu Kombu
Rausu kombu has a very soft fiber and is known for its broad and thin shape. When soaked in hot water, it gives a slimy, gooey texture and a rich umami flavor. Rausu creates a very richly flavored dashi, with a darker brown color than Rishiri or Makombu dashi. It is well used for Kobujime (raw fish refined by wrapping it in kombu) and Kobumaki (kombu rolls filled with cooked fish).

Hidaka Kombu
Hidaka kombu has soft fibers and is usually whole. This whole kombu is used for simmered dishes, Kobumaki (rolled kombu filled with cooked fish) and tsukudani condiments (kombu candied in a mixture of soy sauce, mirin, sake, sugar). It can create a darker brown, less sweet dashi with a strong kombu taste. It is not usually used to make traditional dashi.

Makombu
Makombu is a high quality kombu such as Rishiri or Rebun. Its fiber is softer than Rishiri. It is mainly used in the Osaka area, while Rishiri is popular in Kyoto. Makombu dashi has a rich golden color and a mild, sweet flavor. Its shape is wider and thicker than the others. It is used for cooking like shio-kombu and tsuo and tsukudani-kombu. It is also favored for making special forms of kombu by hand and presented at religious events as special offerings.