Nihon Chomiryo Tabi
What resident microbes are
- They are the yeasts and lactic acid bacteria living in the barrels and the beams. Identical ingredients taste different from brewery to brewery because these microbes differ completely from one place to the next.
- Most breweries add yeast and lactic acid bacteria deliberately, as a starter culture, to keep fermentation steady.
- Leaving it to the resident microbes instead means no one puts the microbes in. What already lives in the barrel decides the taste.
- A kioke is the dwelling itself. Microbes that have lived on for a hundred years and more are what make that brewery's taste.
You may have seen "tennen jozo" printed on a bottle of shoyu (soy sauce). Behind those words is the work of living things too small to see: the kuratsuki microbes that have made a home in the brewery.
Soybeans, wheat, salt, water. The ingredients hardly change from one shoyu to another. So why does the taste change from brewery to brewery? Because the microbes working inside the barrels differ completely from one place to the next.
Microbes that live for a hundred years in barrels and beams
In shoyu brewing, koji (the fermentation culture Aspergillus oryzae) is added to steamed soybeans and roasted wheat to make shoyu koji, and brine is added to that to make moromi (the fermenting mash). What goes to work while that moromi ferments and ages is yeast and lactic acid bacteria.
At most breweries, that yeast and those bacteria are added deliberately as a starter culture. It keeps quality steady and lets the pace of fermentation be controlled.
At a brewery that has used wooden barrels for many years, on the other hand, yeasts and lactic acid bacteria have settled on their own into the grain of the barrels and into the beams and walls of the building. These are the kuratsuki microbes. With no starter culture added, the moromi ferments on these residents alone. Even with the same ingredients, the combination of microbes living there differs by brewery, and so does the taste.
Kioke are down to just 1% of the whole
Wooden barrels, once the mainstay of shoyu brewing, are now a rarity. As stainless steel tanks spread, being easier to brew in and easier to manage, the share of shoyu in Japan made in kioke (wooden barrels) is said to have fallen to about 1%.
As kioke disappear, so does the habitat of the resident microbes inside them. If efficiency comes first, that outcome is hard to argue with. Even so, a handful of breweries keep choosing the harder path of kioke and tennen jozo.
The one brewery in Japan that does no temperature control
In Aisho (愛荘町), Shiga Prefecture, on the bank of the Echi River (愛知川) crossing the Koto plain, stands Marunaka Shoyu, founded in the Kansei era, around 1800. The 4 buildings of the brewery are designated as national Registered Tangible Cultural Properties, and the place is known as the "Nihyakunen-gura" (二百年蔵), the two-hundred-year brewery.
What marks this brewery out is how completely it trusts its resident microbes. No heating, no artificial temperature control of any kind: it still keeps to an older method that leaves fermentation to the microbes at work and the shift of the seasons. This is said to be the only such practice left in the country. Aging normally runs 3 years. Domestic soybeans, domestic wheat, and natural sea salt are the only ingredients, and the finishing of the shoyu is left to microbes that have lived there for 200 years.
The shoyu that comes out is a koikuchi (the standard dark shoyu) with no hard edges, startlingly round. Chefs call it the supporting player that lifts the lead, and dissolved in that taste is the time held by the buildings themselves.
Ways to enjoy tennen jozo shoyu
- Rice with a raw egg: raw and unheated, this is the bowl where the difference in aroma reads most plainly
- Chilled tofu and sashimi: as a finishing drop, it brings forward the aroma the resident microbes built
- Simmered dishes: it carries enough savor to settle the taste without dashi
- Grilled onigiri: heat brings out a toasted note and shows another face of it
There is this much variety inside the single word "shoyu." For your next bottle, taste the story of the microbes in the barrel along with it.
Frequently asked questions
What kind of microbes are kuratsuki microbes?
Yeasts and lactic acid bacteria that have settled on their own into wooden barrels used over many years, and into the beams and walls of the brewery. The mix and the species differ by brewery, so the same ingredients made by the same method taste different once the building changes. Shoyu fermented and aged by these resident microbes alone, with no purpose-grown starter culture added, is called tennen jozo (naturally brewed, no temperature control).
How much shoyu is still brewed in kioke today?
Of the shoyu on the market in Japan today, roughly 1% is said to be brewed in kioke. As mass production in stainless steel tanks became the norm, kioke and the community of resident microbes that live in them have become a rare thing.
Where can I buy shoyu brewed with resident microbes?
We would point you to Marunaka Jozo Shoyu from Marunaka Shoyu in Aisho, Shiga Prefecture. Founded in the Kansei era, it works out of a "two-hundred-year brewery" whose 4 buildings are registered as national Registered Tangible Cultural Properties, and it keeps to an older method with no temperature control at all, leaving everything to the resident microbes. Pour it raw over rice with an egg, or over chilled tofu, and you can taste the difference in aroma.
