Vol. XXVIII · The Cuisine of Japan Plate 2 of 11dashi, 出汁, 一番出汁, 二番出汁, kombu, 昆布, katsuobushi, 鰹節, shiitake, 椎茸, 精進出汁, vegan dashi, mizudashi, 水出し, glutamate, inosinate, guanylate, extraction temperature, umami synergyMF

Dashi in Depth.

Kombu boiled hard tastes of the sea and turns the broth slimy. Held at 60 °C for an hour it gives almost all its glutamate and none of the slime.

XXII.3 showed why dashi tastes so savoury: glutamate from kombu and inosinate from katsuobushi multiply each other's umami (XI.5). Here is how cooks get them out. Kombu's glutamate sits in its tissue and diffuses out slowly; the rate rises with temperature (V.10). But near the boil kombu also releases alginate slime and sulphurous, iodine-like "seaweed" notes, so the classic method soaks kombu in cold water and heats it slowly, removing it just before the boil — or, better, holds it at about 60 °C for an hour; mizudashi (水出し) simply leaves it in cold water in the fridge overnight. Katsuobushi, shaved thin, gives up its inosinate and smoky aroma in a minute or two of steeping in water just off the boil; squeezing or long boiling makes the dashi cloudy and bitter.

Ichiban dashi (一番出汁), the first extraction, is clear, fragrant and delicate, for clear soups (吸い物) and chawanmushi. Niban dashi (二番出汁) simmers the used kombu and katsuobushi again, often with a little fresh katsuobushi, for 10–15 minutes: stronger, less refined, for miso soup and simmered dishes. Shōjin dashi (精進出汁), the dashi of Buddhist temple cooking, replaces fish with dried shiitake, whose guanylate synergises with glutamate even more strongly than inosinate does. Instant dashi granules are mostly salt, MSG and nucleotides: savoury, but missing the aroma. The workshop extracts kombu.

Below: the share of kombu's glutamate extracted over the minutes you choose at the temperature you choose, with a teaching index of slime and seaweed off-notes, and the umami of the dashi as MSG equivalent with katsuobushi, shiitake or kombu alone (Yamaguchi's synergy; guanylate counted 2.3 times inosinate).

What you will learn
Workshop
Teaching extraction model: glutamate extracted = 1 − e^(−k t), k = 0.02 per minute at 60 °C with activation energy 40 kJ/mol; off-notes = (1 − e^(−0.05 t)) ÷ (1 + e^(−(T − 85) ÷ 4)). Yields per litre as in XXII.3: 10 g kombu up to 0.025 g/dL glutamate; 20 g katsuobushi 0.024 g/dL inosinate; 10 g dried shiitake 0.004 g/dL guanylate, counted 2.3 × (Yamaguchi 1971). Umami as MSG-equivalent g/dL (Yamaguchi 1967).

Low and slow for kombu, quick for katsuobushi

In the teaching model an hour at 60 °C extracts about 0.70 of kombu's glutamate with no off-notes; ten minutes near the boil extracts 0.55 but scores 0.36 on the off-note index — slime and smell; a night in the fridge (ten hours at 10 °C) reaches 0.61. With 20 g of katsuobushi steeped in, that hour-long kombu dashi tastes like 0.53 g/dL of MSG; with dried shiitake instead, 0.21; kombu alone only 0.017 — synergy does most of the work.

Ichiban dashi (1 L): wipe 10 g kombu, soak it in 1.1 L cold water 30 minutes, then hold at 60 °C for an hour (or heat slowly and remove just before the boil). Remove the kombu, bring to just below the boil, take off the heat, add 20 g katsuobushi, steep 1–2 minutes until it sinks, and strain through a cloth without pressing. Niban dashi: simmer the spent kombu and katsuobushi in 500 mL water 10 minutes, add 5 g fresh katsuobushi, steep and strain. Shōjin dashi: soak 10 g kombu and 3–4 dried shiitake in 1 L cold water overnight in the fridge. Use dashi within two or three days, or freeze it.

At the stove

Make two small kombu dashis, one held at 60 °C for an hour and one boiled ten minutes. Taste and smell them side by side before adding anything.

Kombu from Hokkaidō reached Kyoto and Osaka by the "kombu road" of Edo-period coastal shipping, and on to Okinawa and China; Osaka's soft-water dashi made from Rishiri and Ma-kombu is still considered the benchmark of Kansai cooking.

Terms

一番出汁
First dashi: clear and fragrant, for clear soups.
二番出汁
Second dashi: re-simmered, for miso soup and simmering.
精進出汁
Temple dashi of kombu and shiitake, without fish.
水出し
Cold extraction overnight.
Kombu: about 60 °C for an hour or cold overnight; near the boil it turns slimy and smelly. Katsuobushi: 1–2 minutes just off the boil, don't squeeze. First dashi for clear soups, second for miso and simmering; shiitake replaces fish.

Sources

  1. S. Yamaguchi, "The synergistic taste effect of monosodium glutamate and disodium 5'-inosinate", J. Food Sci. 32, 1967: y = u + 1218·u·v, concentrations in g/dL.
  2. S. Yamaguchi et al., "Measurement of the relative taste intensity of some L-α-amino acids and 5'-nucleotides", Journal of Food Science 36 (1971) 846–849: in synergy with glutamate, guanylate (GMP) is about 2.3 times as effective as inosinate (IMP).
  3. S. Tsuji, Japanese Cooking: A Simple Art, Kodansha, 1980 (rev. 2006).
  4. A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.