Miyagino Natto Factory Aging Building

Where the Beans Become Natto

The Miyagino Natto Factory Aging Building (宮城野納豆製造所熟成棟, Miyagino Nattō Seizōsho Jukuseitō) is a single-storey factory building of about 1934 at the Miyagino Natto Factory in Ichomachi, Miyagino-ku, Sendai, used to ferment and mature packed natto, and was listed as a Registered Tangible Cultural Property on September 10, 2019.

It adjoins the east wing of the production building. Under a long Kirizuma-zukuri gable roof carried on a timber truss, a rail track runs straight down the middle, directly beneath the ridge. Small fermentation rooms line the south side of the track; the north side is where the finished natto is cooled and sent out.

The building is timber-framed and single-storey with a metal-sheet roof and a building area of 272 square metres. It was extended in the years after the war and renovated in 2017.

Why It Was Registered

Registered as number 04-169 for its contribution to the historic landscape, the Miyagino Natto Factory Aging Building is called by the Agency for Cultural Affairs the backbone of a modern food factory, fitted with a new type of fermentation room developed on the premises.

That room is most likely the Miura-style fermentation chamber, or bunkashitsu, devised by the founder Miura Jiro. Sendai's Board of Education credits it with helping to establish the modern way of making natto. Cooking and inoculating the beans is only half the job; what decides the result is a night or so at steady warmth and humidity, and this building houses exactly that step.

The company tells how the idea came about. After repeated failures to control the temperature, Miura spotted a snow-covered compost heap beside a farm road with steam escaping from a hole in the snow. That hole, the story goes, became the ventilation opening in the ceiling of his fermentation rooms.

What to Look For

The fermentation rooms are called muro. According to the company, the rooms used until 2013 still survive inside, each with a hole in the ceiling that was opened and closed to adjust temperature and humidity. Machines that regulate both automatically have since taken over.

The track through the Miyagino Natto Factory Aging Building is the factory's circulation made visible. Packs from the production building arrive by trolley and are distributed along the line of rooms, and the company says it still uses a trolley built in the early Showa years. Rooms to the south, cooling and dispatch to the north: the plan moves the product in one direction from start to finish.

From outside it is an unassuming single-storey shed with a long gable attached to the production building. A room built to hold in heat and moisture has little use for windows, and the plain walls reflect that.

Visiting

The Miyagino Natto Factory Aging Building is part of a working factory; its interior is closed and the walled site cannot be entered. The company's factory pages and video show the ceiling vents and the trolley.

No notice on photography was found. Directions and contact details for enquiries are on the Miyagino Natto Factory page.