Every year the room takes a resident brewery, and for 2024 and 2025 it has been Tedorigawa in Ishikawa. Yuki writes to them; they write back; some of it is worth passing on.
The question we put to them last autumn was a simple one and the answer was not. Why, when almost every brewery in Japan now uses a purchased lactic acid starter, does Tedorigawa still run a yamahai mash on part of its production, given that yamahai takes twice as long, fails more often, and produces a sake that is harder to sell?
Because the lactic acid our own room makes is not the same lactic acid you can buy. It is slower and it is ours.
That is a paraphrase of two paragraphs, but it is the substance. In a modern mash you add lactic acid at the start, which acidifies the mash immediately and keeps out everything that should not be there. In yamahai you wait, and let the ambient lactic acid bacteria in the brewery itself do the work over two to four weeks. You are betting the batch on the microflora that live in your own walls.
What comes out is broader and more savoury, with a lactic depth that reads almost like a soft cheese rind at the back of the palate. It is the pour we send with the anago, because the tsume glaze is sweet and needs something with earth underneath it.
The third generation could have stopped. The letter is fairly clear that stopping was discussed, in the nineteen-nineties, and that the argument against it was not commercial.