醤油 Shoyu

Shôyu (soy sauce)

In ancient times, the Japanese made seasonings by fermenting and salting i) herbs, ii) cereals, iii) flesh (cf. salt). They can be called primitive forms of Shôyu, but the soy sauce itself was born in the 14th century as a by-product of Miso. It was the juice accumulated in a Miso bucket. This kind of Shôyu is used even today and called “Tamari-Shôyu” (literally, the accumulated Shôyu)


At the beginning of the 17th century, Edo (today’s Tokyo) became a center of politics and its population began to increase. Edo (Tokyo) faces the sea and people there eat a lot of fish. To mask the smell of fish, strong soy sauce was invented in the suburbs of Edo. This is “Koi-kuchi Shôyu”.

This sauce is dark in color and light-colored Shôyu was born in the West to keep delicate colors of the cuisine. It is “Usu-kuchi Shôyu”. Since then, the difference between the West and the East especially in food culture has become clearer.

At the end of the 17th century, a new way was invented in Yanai (Yamaguchi prefecture) to get a sweeter Shôyu. This Shôyu is called “Sai-shikomi” which literally means repeated fermentation. In this method, the sauce is fermented almost twice

At the beginning of the 19th century, the Shôyu whiter than Usu-kuchi Shôyu was born in Hekinan (Aichi prefecture). It requires more wheat than soybeans and called “Shiro-Shôyu” which means white Shôyu.

Production method

Koi-kuchi , the most popular Shôyu, is produced as mentioned below:

1) mix cooked soybeans and broken wheat (the amount of these two is the same)

2) add Koji-bacteria to make Koji

3) add salt water and make it ferment

4) after fermented enough, extract the juice from 3). This juice is called ‘Nama-Shôyu’ (raw shouyu)

5) heat 4) for sterilization, color adjustment, obtaining aroma etc.


-Usu-kuchi (light Shôyu) is made by the same process as above, but the fermentation period is shorter to avoid gaining dark color. For this reason, more salt is added to finish the fermentation during limited period. Sweet sake or syrup is sometimes added at the end of this process.

– Tamari (accumulated Shôyu) is originally made from only soybeans. Recently some wheat (about 10% of the total amount) is added to gain a flavor.

– Sai-shikomi (repeated fermentation) is made by adding the Nama- Shôyu made by the process 4) mentioned above which is already fermented. Thus fermentation is repeated almost twice.

– Shiro (white Shôyu) is made from cooked wheat and small amount of broken soybeans (the opposite proportion). The fermentation period is shorter than others.


 Bacteria active in the Shôyu

aspergillus sojae 

It makes the fundamental flavor of Shôyu by breaking down the protein of soybean into amino acid and the starch into sugar such as glucose.

lactic bacteria

It gives a deep flavor by making lactic acid and acetic acid.


 It increases the aroma by making alcohol etc.

Characteristic in cooking

Shôyu can sterilize bad bacteria by salt, lactic acid, alcohol etc. This is one of the reasons why sashimi (raw fish) is dipped in a small dish containing Shôyu and horseradish, or grated ginger. Salmon eggs called “Ikura” are often pickled in Shôyu to keep their freshness. In addition, Shôyu can eliminate the bad odor of fish or meat by wrapping them.


Moreover, we cannot forget the aroma of burnt Shôyu. When amino acid and sugar are heated together, they send an appetizing savor (amino-carbonyl reaction). Senbei (puffed rice biscuit) uses this reaction.

Difference between the West and the East

Since Japan is a long and narrow country, the climate is totally different depending on the regions. The south belongs to subtropical zone, the middle to temperate zone and the north to subarctic zone, which varies the average temperature from 6 to 22 ° C from north to south. As a result, culture can also be different in each region. But it is largely divided into two: the West and the East. The center of the West is Kyoto and the East is Tokyo.

As for food, the biggest difference is soup. The water of the West is sweet and goes well with broth of seaweed. They add light soy sauce (usu-kuchi Shôyu), tender in color. It is for this reason that the soup of the West is soft and refined.


On the other hand, the water of the East is hard and goes well with bonito broth. They add strong soy sauce (koi-kuchi Shôyu), dark in color. As a result, the sauce of the East is full-bodied, both sweet and salty.

Another interesting difference is how to prepare the eel.

In the west, eel is cut from the belly side. There is a saying “open our stomachs” which means to verbalize frankly our idea or feeling. In general, people in the West (especially Osakaïst) tend to communicate more directly than people in the East. They like to talk and laugh a lot.

cut by the belly side
cut by the belly side
cut by the back side
cut by the back side

On the other hand, eel is cut by the back in the east. The action of cutting the belly reminded warriors (samurai) the hara-kiri. “Hara” means the belly and “kiri” means cutting. The “hara-kiri” is a ritual suicide that the samurai had to execute when they had committed an unpardonable fault. Many warriors (samurai) lived in Edo, today’s Tokyo.

Samurai preferred to stay in the left to draw his sword quickly at the right moment. Some believes that this is the reason why people place themselves in the left on the escalator in Tokyo.On the contrary, people place themselves in the right in the West where many merchants lived. Merchants preferred to stay in the right to protect their belongings by holding them in the right hand.

This story also indicates that most of the Japanese are right-handed. In Japan, parents tend to give their children a correction when they are found to be a southpaw.

the West
the West
the East
the East