Why a Bottle Shop in Okinawa Sells Kombu

We are a small bottle shop in Yomitan, Okinawa. Alongside the natural wine and the junmai sake, there is a shelf of kombu.

People ask about it. The short answer is that we choose food the same way we choose drink: it has to taste good, and the way it is made has to make sense to us.

That answer is not very interesting on its own. What is interesting is what turned up when we looked closely at one kombu maker. If you have never made dashi, this is also a short introduction to it. If you already cook with it, there are one or two things here that may still catch you out.

First: what dashi actually is

Dashi is the basic savoury broth of Japanese cooking. It sits underneath miso soup, simmered dishes, noodle broths and a great deal else.

If you come from a European kitchen, it helps to know what dashi is not. There is no roasting, no bones, no aromatic vegetables, no long simmer, no reduction. Most dashi is finished well inside half an hour, and much of that is soaking.

The two classic ingredients are both dried. Kombu is kelp: harvested, dried and matured. Katsuobushi is what you will see sold in English as bonito flakes — or, to be more accurate, skipjack tuna. The fish is simmered, smoked and dried, in the finest grades also cultivated with mould, then shaved into paper-thin sheets.

You steep the kombu in water and take it out before the water boils. You add the katsuobushi briefly, then strain. That is the whole process.

The important word here is extraction. A French stock concentrates its ingredients by cooking them down. Dashi pulls a particular set of soluble compounds out of dried ingredients and leaves the rest behind. Hold on to that idea. It comes back later, and it is ultimately why this shelf exists.

The maker: Konbu Doi

Our kombu comes from Konbu Doi, a kombu shop in Osaka founded in 1903. It is run today by the fourth generation, Junichi Doi, who writes and speaks a good deal about kombu, dashi and food culture.

Being long-established is not why we stock it. We stock it because it tastes good, and because each product turns out to have a reason for being shaped the way it is.

Konbu Doi’s Nippon no Dashi (a dashi pack) is the clearest example.

Why Nippon no Dashi comes in two bags

A dashi pack is a convenience product: pre-portioned ingredients in a filter bag, rather like a large tea bag. Drop it in water, heat, remove.

Konbu Doi’s Nippon no Dashi does something odd. The kombu and the katsuobushi come in separate bags. You use the kombu first, and the katsuobushi after.

That is more work. One bag would be easier. But kombu and katsuobushi want different handling — different temperatures, different timings — and putting them in the same water for the same length of time means one of them is treated wrong. Doi has written that they tried a combined version: the katsuobushi came forward, and the kombu never quite arrived.

So the shape of this product ends up reproducing the traditional order. Kombu first, katsuobushi second. It is convenient, but not at the cost of the part that matters. Doi calls this idea “convenient, but real”.

Once you notice it, the split pack stops looking like a quirk and starts looking like an argument.

A kombu merchant who avoids the word “umami”

Here is the part we find hardest to forget. Konbu Doi is reluctant to use the word umami.

Which is strange. Umami is the fifth basic taste, alongside sweet, salty, sour and bitter — and kombu is where it was found. In 1908 Kikunae Ikeda isolated glutamate from kombu broth and gave the taste its name. Kombu is the origin story.

The science is good, too. Glutamate alone reads as savoury. But add a compound from a different chemical family — inosinate, which is what katsuobushi brings — and the two together taste considerably stronger than the sum of their parts. This is umami synergy, and it has been traced down to the receptor.

So Japanese cooks combining kombu and katsuobushi were relying on a real mechanism, centuries before anyone could describe it.

But the synergy is fussier than it is usually made to sound.

It needs two different families. On one side sits the amino-acid group: kombu, and also aged cheese. On the other sits the nucleotide group: katsuobushi, and dried shiitake. You need one from each.

Which means a rule you hear constantly — fermented things go with fermented things — does not hold, at least not through this mechanism. Aged cheese and sake are both sitting on the amino-acid side. This particular synergy never fires. Cheese and sake can work beautifully, but when they do, something else is doing the work. We wrote about that separately in Why Cheese Works with Sake — and When It Doesn’t.

There is a second limit as well. Synergy occurring is not the same as the result tasting good. Push it and a dish turns heavy. The mechanism predicts intensity, not deliciousness.

Which brings us back to Doi. If you say kombu is good because it is high in glutamate, the obvious next question is: then why bother with the kombu? Add the glutamate and skip the kelp.

Except that it plainly does not work, and anyone who has tasted a well-made kombu broth knows it does not. There is sweetness, there is aroma, there is a long finish. None of that is contained in the word glutamate.

Science is a tool for understanding flavour. It is not a guarantee of it. That distinction is, we think, why a kombu merchant would rather talk about this kombu than about umami in general.

What the broth leaves behind

Now back to that word: extraction.

Doi expected the minerals in kombu and dried sardines to end up in the broth. When the analysis came back, they largely had not. Calcium and magnesium mostly stay in the spent ingredients — in the soft, wet kombu you were about to throw away.

Set that beside everything above and it becomes rather funny. We reduce kombu to a single compound in conversation, and even in strictly compositional terms, the broth is only taking part of it.

So Konbu Doi makes things for eating the leftovers. Mineral Irikon is roasted kombu, small dried sardines and soybeans, taken to a crisp. The detail we like is this: the sardines are seasoned before roasting, but the kombu is not. It is roasted plain and finished with a little pressed sesame oil. The soybeans are roasted plain as well. They are letting the kombu be the flavour.

The same thinking runs along the rest of the shelf. Shittori Furikake, a rice topping, is built from what comes out of making their concentrated dashi. Umekatsukon simmers shredded kombu and katsuobushi with plum from Wakayama. Hosogiri Shiofuki is finely cut kombu, simmered in seasoning and dried.

None of this is really a food-waste story, although it happens to be one. It is a decision to treat kombu as an ingredient rather than as a device for making broth.

The most beautiful thing in the shop costs 250 yen

Konbu Doi sells natural kombu from Kakkumi Bay in Hokkaido that runs to several thousand yen for a single sheet. That end of the business is real.

But in a post from 2020, Doi wrote that the shop should be moving away from gourmet and towards everyday food — that the aim is honest daily food that is inexpensive and good, without giving up the no-additives standard.

Then this:

A child from the neighbourhood buys the 250-yen Shittori Furikake, absolutely delighted. That scene is probably the most beautiful part of Konbu Doi.

(That was the price in 2020, before recent inflation.)

Someone who has spent a career on kombu worth thousands of yen a sheet picked, as the most beautiful thing in it, a child buying furikake with their own money.

Our own child loves the stuff. At dinner time they go and fetch it from the fridge unprompted. It is katsuobushi, kombu and tiny shrimp, and you can taste each of them.

Running a shop, you notice that good products drift towards becoming special-occasion products. But the ones worth choosing are usually the ones that quietly run out.

Okinawa grows no kombu, and eats a great deal of it

There is one more reason this shelf makes sense here.

Kombu does not grow in Okinawan waters. It is a cold-water seaweed, and the kelp beds are far to the north, off Hokkaido. And yet Okinawa has old, everyday dishes built on eating kombu itself. Kuubu irichii — shredded kombu stir-fried with pork and vegetables — is a standard.

The reason is the Kombu Road. In the Edo period, kombu harvested in Hokkaido travelled by kitamaebune, the northern trading ships, down the Japan Sea coast to Osaka, then on through Satsuma to the Ryukyu Kingdom, and from there to Qing China. Ryukyu was an important staging point in that trade.

Some of what passed through stayed. Kombu entered the Okinawan kitchen and, over a long stretch of time, stopped being an imported trade good and became local cooking.

Which is why here, kombu is not simply something you make broth from. It is something you eat.

In our own house, the kombu from the dashi pack goes into curry, into fried rice, or into okara irichii. Having given up its savouriness, it takes on the oil and liquid around it and behaves like a vegetable. In Okinawa this is not a clever trick. It is just what you do.

Trying it at home

The two-bag pack makes a good experiment, because it lets you taste the mechanism rather than read about it.

Steep the kombu bag in water — cold, for half an hour or so — then heat gently and take it out before the water boils. Taste it on its own first. It is subtle, faintly sweet, a little oceanic, and it may well seem underwhelming.

Now add the katsuobushi bag for a minute or two, strain, and taste again. The change people expect is “stronger”. The change most people actually notice is that the flavour stops stopping. It carries on through the mouth instead of fading at the edges. That is the synergy.

If you want a version without fish, use dried shiitake in place of the katsuobushi. In a trained-panel study, the guanylate in dried shiitake worked at least as well as the inosinate in katsuobushi, which is why Japanese temple cooking manages perfectly well without fish. The aroma is completely different, so choose by dish rather than by strength.

Finally, keep the spent kombu. Slice it thinly into a stir-fry or a rice dish, or simmer it down with soy sauce and mirin. If it tastes of nothing at all, that tells you something useful about the kombu you bought.

From Osaka to Okinawa, again

Kombu grown off Hokkaido went to Osaka, then onward to Okinawa, and became part of how this island eats. Now the products of an Osaka kombu shop sit on the shelf of a small shop in Okinawa.

We are not re-enacting the Kombu Road. But keeping something that took centuries to become local food in ordinary daily use seems like a reasonable thing for a shop to do.

We do not stock things because the philosophy behind them sounds admirable. It has to taste good, and it has to be usable.

Follow the reason a thing is shaped the way it is, though, and you generally end up seeing what the maker cares about. Those are the things we want on the shelf.

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Related Articles

• Why Cheese Works with Sake — and When It Doesn’t — what is actually at work when a pairing succeeds, and when the umami explanation does not apply.
• How We Choose What Goes on Our Shelves — the thinking behind what we stock, drink and food alike.
• A Map of Aroma Compounds — where the aromas in food and drink come from, family by family.

Products in this article

• Nippon no Dashi (dashi pack) / Konbu Doi — Osaka. Sold as “the traditional Japanese broth”. Shirokuchihama natural kombu and Kagoshima katsuobushi, in separate bags to be used in sequence. The contents are worth eating after straining.
• Umekatsukon / Konbu Doi — Osaka, 80g. Shredded kombu and katsuobushi simmered with plum from Sanko Farm in Wakayama. Good on hot rice.
• Hosogiri Shiofuki / Konbu Doi — Osaka. Finely cut kombu, simmered in seasoning and dried. For rice, onigiri or scattered over a salad.
• Mineral Irikon / Konbu Doi — Osaka. Roasted kombu, small dried sardines and soybeans. The kombu is roasted unseasoned and finished with pressed sesame oil. Available in store.
• Shittori Furikake / Konbu Doi — Osaka. A rice topping of katsuobushi, kombu and tiny shrimp, made from what comes out of producing their concentrated dashi. Available in store.
• Kizami Tennen Ma-Kombu / Konbu Doi — Osaka. Pre-cut kombu, ready to use in simmered dishes, rice or vinegared salads. Available in store.

Stock and prices are on the individual product pages, which are in Japanese. If you are in Okinawa, everything above is on the shelf in Yomitan.

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