Chronicle of Hekinan

Chapter Five

The Kura — Architecture that Joins the Ferment

第五章 — 蔵・発酵に加わる建築

Introduction — Vessel, or Apparatus?

In the chapters before this, we followed the culture of fermentation that gathered in this single soil — a ground where the sea road gave birth to mirin and, two centuries ago, to white soy sauce. Yet one character in that story has gone unnamed. The building.

When we speak of fermentation, we usually think of the ingredients and the maker. Rice, kōji, water, and the human hand. The building, we tend to assume, is no more than a vessel — a container in which the work is kept.

This chapter wishes to overturn that view. The kura — the brewing storehouse — is not a vessel that holds fermentation. The kura itself takes part in it. It holds the temperature, tempers the moisture, lets the microbes dwell, and carries time. The building is an apparatus of fermentation.

Let us follow this question — vessel, or apparatus? — along a single thread: mirin. Why mirin? Because mirin is a singular, sweet brew among ferments, and because its sweetness depends so deeply on the place where it is made, and on the time that passes there.

I. The Kōji Room — A Climate Machine Made of Wood

Where is the sweetness of mirin born? Its starting point is a small room: the kōji room (kōji-muro).

Mirin is made by combining steamed glutinous rice with rice kōji, adding shōchū to the mash, pressing it, and letting it rest for half a year, a year, or longer.1 The key to that first step — turning rice into sweetness — is held by the kōji. The saccharifying enzymes the kōji carries — the family of enzymes called amylase — break the starch of the rice, little by little, into sugar.2 That clear sweetness of mirin is the crystallisation of this patient, enzymatic work.

The room where that kōji is raised is the kōji room. Kōji mould is a delicate microbe, swayed by the slightest shift in temperature or humidity. And so the kōji room is built sealed from the outside air, holding a temperature of around thirty degrees and a steady humidity.2 Long before it could borrow the power of electricity, this room made a climate for the microbe with the human hand alone.

What deserves attention here is the material of its walls. The kōji room has, from old, been lined with boards of cedar (sugi). Cedar regulates humidity — drawing moisture in, and breathing it out, it gently settles the air of the room.3 Today many breweries choose walls of stainless steel or resin, easier to clean and to keep free of stray microbes. That is a rational choice. And yet there are breweries that go on choosing walls of wood, deliberately, to keep the moisture-regulating virtue that has been handed down as good since old time.3

Here is the first answer. The kōji room is not a mere box for keeping a microbe. The wood itself, as a material, performs the work of tempering humidity. The building actively makes the environment the microbe needs. This is no longer a vessel. It is an apparatus.

II. To Halt, and to Wait — The Time the Kura Holds

The kōji begins to turn rice into sugar. But the sweetness of mirin holds one more device within it: the work of halting.

In ordinary sake-making, the sugar that is born would be turned, by the work of yeast, into alcohol. The sugar is spent, and becomes drink. In mirin, however, shōchū is added from the very start of the mash, so the alcohol of the mash runs high. This high alcohol keeps the yeast from fermenting.4 The sugar, its road to alcohol cut off, has nowhere to go. And so it gathers, just as it is, within the vat. Sweetness with nowhere to flee, quietly growing denser — this is the true nature of mirin's sweetness. Seventy to eighty per cent of the sugar in hon-mirin is glucose.5 At the same time, that high alcohol stands as a guard against the breeding of stray microbes.4

Once the sweetness has gathered in the vat, what remains is to wait. Half a year, a year, in some cases several.1 Through this maturing, sugars and amino acids interlace, the colour deepens to a clear amber, and aroma is born.

What holds this long wait is the storehouse of keeping — the kura. And here, too, the building is at work. What mirin's maturing needs is this: not to hurry, a temperature that does not swing widely, a humidity held even. The traditional Japanese storehouse — the dozō — is built for exactly these conditions.

III. Breathing Walls — The Microclimate of Earth and Plaster

The dozō is a building of thick earthen walls laid up over a timber frame, finished at the surface with plaster.6 The brewing storehouses that make sake and soy sauce are nothing other than a kind of this dozō construction.6

Those thick earthen walls hold a fine insulation. Cool in summer, warm in winter, they keep the inner temperature calm.6 However hot or cold it grows outside, within the kura the air scarcely changes its face across a day. The steady temperature that mirin's long sleep requires is here.

And earthen walls and plaster hold one more work: the regulating of moisture. The wall of earth draws moisture in when the air grows damp, and breathes it out when the air grows dry.7 The wall is breathing. Within that breathing membrane, the humidity is held even, without wide swings. It is for just this reason that the kura has, from old, been used as a place to store what is precious, guarded from damp.6

Set this beside the modern way of thinking, and the singularity of this architecture stands out. To hold temperature and humidity steady, the rational impulse is to seal, and to control by machine — to shut out the air, and manage it by numbers from without. That, too, is a kind of correctness.

But the path the dozō chose was the very opposite. Not to seal, but to let breathe. Not to control, but to temper. To let the wall itself draw moisture in and breathe it out, entrusting that work to the nature of the material. This stance of entrusting chimes exactly with the conduct of fermentation itself, which yields — without haste — to the microbe, to time, to the current. The very way the building is made mirrors the philosophy of the ferment.

IV. Kuratsuki — The Terroir of Architecture

Thus far we have seen the building take part in fermentation through temperature and moisture. But its part holds a deeper layer still. Microbes dwell in the building itself.

In a storehouse of old brewing, an ecosystem of microbes belonging to that kura alone has settled into the beams, the pillars, the walls, the tools. These are called the kuratsuki microbes — the resident yeast of the house.8 Without any cultured yeast being added, these resident microbes are taken up of themselves, carry the fermentation, and give rise to a flavour that belongs to that kura alone.8 In recent years, university research has begun to show that these resident microbes do indeed affect the taste and aroma of the sake.9

This fact carries a heavy meaning. It is this: in that building alone can that flavour be born. There is a story of a brewery whose building was swept away by the tsunami, and which — thanks to resident yeast it had entrusted beforehand to a research institute — could resume, in the land to which it moved, the same brewing as before.10 Turn it around: without carrying the microbes out, rebuilding the building would not return the same flavour. The flavour is not in the recipe. It dwells within the building.

When we speak of the character of a land, we use the word terroir, of the vineyard — the thought that soil, climate and terrain decide the taste. But what comes into view here is another terroir. The terroir of architecture. The building itself, where microbes have dwelt and time has soaked in across centuries, carries the character of the flavour.

Here, though, we must say one thing honestly. This work of the resident microbes shows most strongly in brewing that entrusts much to the microbe's own fermentation — sake above all. In mirin, the high sugar and the added alcohol hold stray microbes in check, so the degree to which wild microbes in the walls sway the flavour is, by comparison, small.4 The building's contribution to mirin lies, above all, in tempering temperature and moisture, and in holding the long stretch of time.

And yet mirin is, unmistakably, a part of this soil's culture of fermentation. The mirin of this land was born, in the first place, upon the culture of sake-making and of the shōchū distilled from its lees.11 The world of brewing in which the resident microbes breathe — from that same soil, mirin too was raised. The terroir of architecture is an inheritance shared by the whole of this soil's culture of fermentation.

Conclusion — The Building Is Waiting

What this chapter has shown is another character in fermentation — the building.

The kōji room tempers humidity with its walls of wood, and makes a climate for the microbe. The storehouse of keeping holds the temperature with its thick earthen walls, tempers the moisture with its breathing walls, and carries mirin's long sleep. And in the brewing storehouse, microbes belonging to that building alone dwell, and carry the very character of the flavour. The building is not a vessel that holds fermentation. To hold the temperature, to temper the moisture, to let the microbes dwell, to carry time — it is an apparatus of fermentation, and a participant in it.

When the matured vat of mirin is pressed, a white lees remains. That crumbling lees, the people of old likened to plum blossoms spilling open at their fullest, and called kobore-ume.12 To the pressing-lees they gave the name of a flower. That is how beautiful this sweetness was to them. It is set down even in the Edo-period encyclopaedia Wakan Sansai Zue as a sweet confection.12

The beginning of that sweetness lay in the wooden walls of the kōji room; the deepening of that sweetness lay within the time of the earthen-walled kura.

Stand within the kura, and nothing seems to be happening. No sound, no movement. Only the cool, the dark, the quiet. And yet within that quiet, the building goes on with the longest work of all. The work of waiting.

This building is not a mere vessel for keeping mirin. The building itself is the waiting.

Sources

This text is a chapter of a white paper on the fermentation culture of Hekinan. The facts set down rest on the cited sources. The influence of resident microbes on flavour is chiefly a finding for sake; in mirin, the high sugar and alcohol keep the part played by wild microbes limited, as stated in the text. The building's contribution to mirin lies mainly in the regulating of temperature and humidity and in holding the long maturation. The insulating and humidity-regulating performance of the architecture rests on accounts of traditional building in general, not on measurements of any particular site. Structures and microbial flora particular to individual breweries will be confirmed against primary sources and reinforced in future revisions.

Footnotes

  1. "Knowing Hon-Mirin — The Types of Mirin," Kokonoe Mirin (on hon-mirin being made from glutinous rice, rice kōji and shōchū, pressed and then stored to mature from half a year to a year or longer). https://kokonoe.co.jp/mirin04 ↩ ↩2

  2. "Learning About Kōji-Making," SAKE Street (on the kōji room being sealed from outside air and held at roughly 30 °C with steady humidity, and on the kōji's saccharifying enzymes — amylase — breaking starch down into sugar). https://sakestreet.com/ja/media/what-is-koji-mold ↩ ↩2

  3. "What Is a Sake Brewery's Kōji Room," Anchorman (on cedar's humidity-regulating quality and the traditional cedar-board kōji room) https://anchorman-inc.tokyo/kojimuro-guide / "Tradition Seen in a Rebuilt Kōji Room," Nihonshu Tourism (on a brewery deliberately choosing a wooden kōji room for cedar's moisture-regulating effect, though stainless or resin walls are easier to keep sanitary). https://nihonshu-tourism.com/archives/4704 ↩ ↩2

  4. "How Hon-Mirin Is Made," Kikkoman (on the mash beginning at a high alcohol level so that yeast fermentation does not occur and sugar accumulates, and on alcohol guarding against mould and other contaminants). https://www.kikkoman.co.jp/enjoys/mirin/making.html ↩ ↩2 ↩3

  5. "Let Us Know Hon-Mirin," National Hon-Mirin Council (on 70–80 % of the sugars being glucose). http://zenkokuhonmirin.com/study.html ↩

  6. "Dozō," DAIKEN architectural glossary (on the dozō being a timber-frame, earthen-walled building finished in plaster, with brewing storehouses being one kind, protecting their contents from fire, damp and theft) https://www.daiken.jp/buildingmaterials/glossary/materials/dozou/ / "The Appeal of Dozō Construction," Itō Architectural Design Office (on thick earthen walls giving strong insulation, cool in summer and warm in winter). https://ito-sekkei.co.jp/staff-blog/dozo-dukuri-architecture/ ↩ ↩2 ↩3 ↩4

  7. "Earthen Walls and Plaster," Kosaka Construction (on earthen walls and plaster together regulating humidity) https://www.kosakakensetsu.com/tradition/4.html / "Traditional Japanese Dozō Construction," LIFULL HOME'S PRESS (on plaster's water- and fire-resistance and the earthen wall's humidity-regulating quality, long used in storehouses). https://www.homes.co.jp/cont/press/reform/reform_00356/ ↩

  8. "What Is Kuratsuki Yeast," SAKE Street (on resident "house" yeast that dwells in a brewery, settling on tools and vessels, multiplying of itself and giving a brewery its own character). https://sakestreet.com/ja/media/what-is-kuratsuki-koubo ↩ ↩2

  9. "House Bacteria Affect the Taste of Sake," Toyo University (on the Nishida laboratory showing that a brewery's resident bacteria alter sake-yeast gene expression and thereby affect taste and aroma). https://digitalpr.jp/r/90255 ↩

  10. "The Kuratsuki Yeast Quietly Living in the Walls," Sake World (on a brewery whose building was swept away by the tsunami resuming the same brewing in a new location thanks to resident yeast it had entrusted to a research institute, and on such yeast as part of a brewery's identity). https://sakeworld.jp/trivia/2504-nihonshu-kuradukikobo/ ↩

  11. "Kikuchi-mura's Kobore-ume," Kikuchi-mura (on the fertile Mikawa plain, the flourishing of soy sauce, miso and sake, and Mikawa mirin coming to be made using a shōchū distilled from sake lees; and on Mikawa as one of Japan's foremost mirin regions). https://kikuchimura.jp/?pid=161566665 ↩

  12. "A Phantom Ingredient — Mirin Lees, 'Kobore-ume'," Marugoto Koizumi Takeo Food Magazine (on the white, crumbling mirin lees resembling plum blossoms spilling open at their fullest, hence the name kobore-ume, and on its appearance as a sweet confection in the mid-Edo encyclopaedia Wakan Sansai Zue). https://koizumipress.com/archives/3377 ↩ ↩2