Shoyu, or soy sauce, is perhaps the most ubiquitous and popular condiment in Asia.
Although originally introduced from China, shoyu has become an integral ingredient to Japanese food culture. In essence, shoyu is a combination of water, salt, and kouji-fermented soybeans and rice (or wheat). Below is a quick description of how we make shoyu at home:
Soy beans are softened in water for a night.
The soy beans are then mixed with kouji, or rice fermented with kouji-kin (aspergillus oryzae fungus, see our project titled "Making Kouji").
The beans and kouji are mixed well by hand.
Once the beans and kouji are mixed well together, the mixture is then rested for a few days to aid the process of fermentation
Since heat comes with the process of fermentation, the bean/kouji mixture must be cooled every day so that it does not reach 46 degrees Celcius, the cut-off line in which the kouji fungus will die.
After this step is copmlete, the bean/kouji mixture is ready to be combined with water and salt. We used fresh water that we obtained from the mountain streams, and natural salt.
The beans are carefully placed into a plastic bag within a traditional wooden bucket designed for shoyu-brewing.
Salt water is added into the beans.
The entire combination of salt, water, beans and kouji are mixed carefully but thoroughly by hand.
Once it is thoroughly mixed, the bag is sealed so that unfriendly bacteria cannot contaminate the kouji.
The mixture is rested for a few months, and agitated periodically to accelerate the process of fermentation. Once the liquid turns into a dark brown color, we have successfully made shoyu.
Photos and descriptions by LKO.