Kombu is a general term for brown algae but there are various species of algae. Among them, those most commonly used as dashi materials are makombu, rishiri-kombu, rausu-kombu and hidaka-kombu which are only harvested around the island of Hokkaido in northern Japan.

I use Kombu almost daily to create flavors in rice, pickles and dashi. I really cannot live without the lifestyle of Kombu and the benefits it imparts. The types I use grow five meters long (in two years) off the coasts of Hokkaido. After harvest they are sun-dried before being shipped. Only Kombu which has matured for two years is used for cooking and one-year-old kombu, called ‘water kombu’, does not contain the rich components needed for a good flavor.

Levels of naturally occurring glutamate (mg/100g)

Makombu 3190
Rausu kombu 2286
Rishiri kombu 1985
Hidaka kombu 1344
Naga kombu 241