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Kelp gives Japanese dashi soup its deep-sea flavor

RAUSU, Japan – At 6 a.m. one morning in early August, about 60 fishermen climbed onto one-man boats in Rausu, Hokkaido, Japan, and sailed out to sea.

Kombu, a kelp, is an essential ingredient of dashi soup stock – a key element of Japanese cuisine. It is dried or aged before being used.

Using glass underwater viewing devices, the fishermen peered into the ocean while rummaging for kombu with long two-pronged poles, which wrench the kelp from its roots. The kombu, each piece measuring about 8 to 12 inches in width and about 6.5 to 9.8 feet in length, was hauled into the boats.

Kazuaki Ida, 60, dragged up about 500 lengths of kombu that morning.

“The sea around the Shiretoko [Peninsula] is rich in nutrients, and we can find good kombu,” he said.

When the weather is good, kombu is spread on pebbles to dry in the sun. If it rains, fishermen hang it on the joists of a beach hut.

To smooth out the kombu, the pieces are rolled up, an activity in which the fishermen’s entire families take part. The dried kombu is then piled up, pressed and left to age.

“We do this to let it mature and develop rich taste,” said Noriyuki Yamashita, of Rausu fishery association’s managing department.

The kombu gathered on that August morning will be shipped in October.

Rausu’s kombu has a rich aroma and lends a sweet taste to dashi soup.

At the fishery association’s storage facility, I got the chance to see prime-grade kombu hauled in last year.

On opening the box, I caught a whiff of the ocean. The brownish-red kombu was shiny and coated in a white powder formed from crystallized umami nucleotides.

Kombu grows in cold water; in Japan, about 90 percent of kombu is from Hokkaido. Aside from Rausu, Rishiri kombu and Makombu from Hokkaido are the top brands.

About 18,700 tons of dried Hokkaido kombu was shipped in fiscal 2012.

These days, fewer people are making their own soup stock at home, so kombu consumption is on the decline.

“The careful processing of kombu produces a rich umami [savory flavor] in the soup. I highly recommend kombu to people,” said Yuko Muratsubaki, of the association.