Dashi.
Ten grams of seaweed and twenty of smoked fish flakes in a litre of water, steeped for less than an hour, taste more savoury than a stock simmered all day.
Dashi is a stock made not by long extraction but by quick infusion of two dried ingredients chosen for their umami. Kombu, dried kelp, is rich in free glutamate, which dissolves in warm water; it is steeped at about 60 °C for up to an hour, or brought slowly to just below the boil, and taken out before the water boils, which would release slimy alginates and seaweedy off-flavours. Katsuobushi — skipjack tuna fillets simmered, smoked, dried and fermented to the hardness of wood, then shaved into flakes — is rich in inosinate (IMP); the flakes are added to the hot water off the boil, steeped a minute or two, and strained without squeezing.
Glutamate and inosinate together are synergistic (XI.5): a little of each tastes far more savoury than either alone, which is why dashi's simple infusion is so deep. The first, delicate extraction is ichiban dashi, for clear soups; the spent kombu and flakes simmered again give niban dashi, for miso soup and simmered dishes. Dried shiitake (guanylate) with kombu make a vegetarian dashi with the same synergy. The workshop mixes kombu and bonito.
Below: the glutamate from the kombu and the inosinate from the katsuobushi you choose per litre (teaching extraction yields), and how savoury the dashi tastes as an equivalent concentration of MSG (Yamaguchi's synergy equation, as in XI.5).
- Make ichiban and niban dashi.
- Explain umami synergy in dashi.
- Handle kombu and katsuobushi correctly.
- Make a vegetarian dashi.
Two dried ingredients, multiplied
With 10 g of kombu and 20 g of katsuobushi per litre, the dashi has about 0.025 g/dL of glutamate and 0.024 g/dL of inosinate — tiny amounts — yet on Yamaguchi's equation it tastes like MSG at about 0.76 g/dL, some 15 times what the same amounts would give without synergy. Kombu alone gives 0.025; bonito alone registers almost nothing on this equation, because inosinate tastes of little without glutamate (katsuobushi does carry some glutamate of its own, so it still tastes savoury). That is why dashi needs so little of each, and why miso, soy and mirin build on it so easily.
Ichiban dashi: wipe 10 g of kombu with a damp cloth (do not wash off the white powder, which is glutamate and mannitol); soak it in 1 litre of water for 30 minutes, then heat slowly to about 60–70 °C and hold 30–60 minutes, or bring to just below the boil over 15 minutes; remove the kombu. Bring the water to a boil, take it off the heat, add 20 g of katsuobushi, wait 1–2 minutes until the flakes sink, and strain through cloth without pressing. Niban dashi: simmer the spent kombu and flakes in half a litre of water for 10 minutes and strain. Cold-brewed kombu dashi (overnight in the fridge) is the gentlest of all. Use dashi within two or three days (XXVIII.2).
Make three cups: kombu infusion alone, katsuobushi infusion alone, and the two mixed. Taste each, then the mix, with a pinch of salt in all three.
Terms
- Kombu
- Dried kelp, rich in glutamate.
- Katsuobushi
- Dried, smoked, fermented skipjack tuna, shaved; rich in inosinate.
- Ichiban dashi
- The first, delicate extraction, for clear soups.
- Synergy
- Glutamate and nucleotides multiplying each other's savouriness (XI.5).
Sources
- 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.
- A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.