The ingredient you cannot see

I. The chemistry

Umami is a taste — the fifth, alongside sweet, sour, salty, bitter — produced by glutamate and certain nucleotides (inosinate, guanylate) binding to receptors on the tongue. Kikunae Ikeda identified and named umami in 1908, finding that the specific taste of kombu dashi was produced by glutamic acid in the kelp.

Katsuobushi contains inosinate. Kombu contains glutamate. The combination produces a synergistic effect: glutamate and inosinate together stimulate the umami receptors more intensely than either alone. The synergy is measurable and was understood empirically in Japanese cooking for centuries before it was explained chemically.

II. The temperature

Temperature matters more than any other variable in the process. Kombu should be removed from the water before a full simmer — at approximately 60°C (140°F), glutamate is fully extracted. Left in boiling water, kombu releases mucilaginous compounds that make the dashi slimy.

Katsuobushi goes in after the kombu is removed, when the water has just reached a simmer (90°C / 195°F), not a boil. Boiling extracts bitter compounds. The katsuobushi steeps off the heat at 75–85°C for 3 to 5 minutes. No longer. The full process takes twenty minutes. Rushing it produces a different product.

III. Ichiban and niban

Ichiban dashi — first dashi — is used in preparations where the dashi flavor is primary: clear soups, dipping sauces, chawanmushi. The spent kombu and katsuobushi are not discarded. They make niban dashi — second dashi — simmered with fresh water for 15 minutes.

Niban is less delicate, more assertive, used in miso soup, simmered dishes, and preparations where the dashi is a background element. The Japanese principle of mottainai is in this practice, but so is the understanding that both extractions have value.

IV. The bowl of miso soup

Ichiban or niban dashi, brought to a simmer. Miso paste dissolved in a small amount of the hot dashi before being stirred into the pot. The miso goes in at the end and the soup does not boil — boiling destroys the live cultures in unpasteurized miso and drives off the aromatics.

Tofu in the last minute. Wakame in the last thirty seconds. Scallion at the bowl. Served very hot — not warm, hot. The bowl is held in both hands. The dashi is not visible in any of this. It is the entire reason the soup is what it is.

Recipe — Ichiban Dashi and Miso Soup

Hideo Kobayashi · Osaka · serves 4 · 20 minutes · the first thing to learn

• 1 L dashi
• 10 min to 60°C
• 3–5 min steep
• no boil

Ingredients

• 15 g kombu (dried kelp)
• 20 g katsuobushi (dried bonito flakes)
• 1 L cold water
• 2–3 T miso paste (white, red, or combination)
• 200 g silken tofu, in 1 cm cubes
• 1 T dried wakame, rehydrated
• Scallion, finely sliced, to garnish

The method

1. Place kombu in cold water. Heat slowly over medium-low — raise to 60°C (140°F), about 10 minutes. Remove the kombu just before simmer.
2. Raise heat to a gentle simmer. Add all the katsuobushi at once. Remove from heat immediately.
3. Let steep 3 to 5 minutes — do not stir. Strain through fine mesh with paper towel or cheesecloth.
4. For miso soup, bring 800 ml dashi to a simmer. Dissolve 2–3 T miso in a small amount of hot dashi; stir into the pot. Do not boil.
5. Add tofu in the last minute, wakame in the last thirty seconds. Pour into bowls; scatter scallion. Serve immediately, very hot.

About the contributor

Hideo Kobayashi

Hideo Kobayashi writes about dashi and Japanese cooking fundamentals from Osaka, Japan. He makes ichiban dashi most weekday mornings and keeps niban dashi in the refrigerator for whatever the day brings.

Editor’s notes — the longer view

A note on instant dashi. Dashi powder — hondashi — is in virtually every Japanese kitchen, including most professional ones for staff meals. It is not shameful. The handmade dashi is for the dish that is built around dashi flavor itself.

A note on the kombu. Hokkaido kombu — ma-kombu and rishiri — is the standard for high-end dashi. The white surface dust is naturally occurring mannitol, not mold. Do not wash it off. Wipe lightly with a dry cloth.

A note on storage. Fresh dashi keeps three days refrigerated. Freezes well in ice cube trays for use anywhere a tablespoon of umami liquid is wanted. The frozen version loses some aroma but retains structural taste.

A note on the vegan version. Kombu plus dried shiitake, soaked overnight in cold water, then warmed gently, produces a dashi with deep umami and no animal product. Shōjin ryōri is built on this stock.

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