Natural brew soy sauce
Soy sauce starts with the roasting of wheat over coal. The base mixture of the soy sauce (called moromi) is combined with steamed soybeans. The base mixture is made from koji, that has been cared for both day and night in a stone muro (fermentation room for koji) to ensure a quality product. The moromi, soybeans and wheat, are joined together in a large barrel that exceeds two meters in height and is then stirred with a long wooden paddle in order to fully incorporate the ingredients with the yeast culture of the barrel and the Kura storehouse. Because this is a natural process, depending on the time of year, the natural climate within the Kura is also a factor in this fermentation process.
Roasting the wheat
We have a unique machine for roasting wheat over coal. It was the latest technology when developed in the Taisho era (1912-1926) and is now a rare object in Japan. It took several years to repair because no craftsman could be found to relay the bricks. Whether in operation or not at the time, there is always a fragrant smell of roasting wheat around this machine.
Shikomi – the first procedures in the making of soy sauce
The making of soy sauce starts in the extremely cold snowy winter months. The bright red color of the coal, and the warm light and flames of the charcoal and straw, contrast to the cold white of the snow all around, giving hope and joy to the makers.
We order our coal from Hokkaido and the charcoal and rice straw used to keep the koji room warm are produced by the same locals every year for us.
The temperature of the koji muro (room) is controlled by an underground fire in the hearth on the floor and the air holes in the ceiling. We manage the temperature of this muro day and night because in order to make quality koji, the temperature must be kept at a constant. The koji will be checked often to ensure it is developing as it should, a check made by the koji craftsmen who feels for the growth of Aspergillus oryzae on each grain of rice.
Paddle stirring of the barrels and the ageing process
The resulting koji is transported tray by tray to the five ton barrels that already include all of the other ingredients. The natural Japanese cedar of these barrels has been used for more than 100 years and houses our unique yeast culture (Ishimago Ebisu yeast). Within these barrels the koji will rest and age for a year and a half until it develops into moromi. To ensure the fermentation process of all the ingredients together, the brewer must stir the barrels many times over the year and half period.
Filtering and bottling
The resulting aged mixture is then filtered through hemp to separate the moromi and remaining matter from the soybeans and wheat, from the liquid soy sauce. The soy sauce is bottled by hand at this point as a means of quality control, measured by the scent of the soy sauce.