Soy sauce comes from China. More than two thousand years ago, Chinese cooks were fermenting soybeans with salt into a thick, savoury paste called jiang. Over many centuries, the dark liquid that seeped from those pastes was drawn off and prized in its own right, becoming jiangyou in China and, once the craft had crossed the sea, shōyu in Japan. Good brewers still make it the slow way, from soybeans, roasted wheat, salt, water and a friendly mould, left to ferment for months. Almost everything that makes it taste good comes down to time.
Before soy, there was jiang
The first jiang were not made from beans at all. Early Chinese texts describe pastes of meat or fish fermented with salt, and they were taken seriously. The Analects records that Confucius would not eat a dish unless it came with its proper sauce. Soybeans were cheaper and easier to come by, and by the Han dynasty, which began a little over two thousand years ago, soybean jiang had become a staple. A sixth-century farming manual, the Qimin Yaoshu, gives detailed instructions for making it. The word jiangyou, literally "jiang oil", appears in writing by around the Song dynasty, a sign that the liquid had become something people bought and cooked with in its own right.
A monk, a miso barrel and a happy accident
Japan had its own fermented seasonings, called hishio, from early times. Its soy sauce, though, has a founding legend. The story goes that in the thirteenth century a Buddhist monk named Kakushin returned from studying in China with a method for making miso, and taught it in the town of Yuasa, on the coast south of Osaka. The liquid that pooled at the bottom of the miso tubs turned out to be delicious, and the people of Yuasa began to make it on purpose.
Whether it happened quite like that, nobody can say. What is certain is that Yuasa's brewing tradition is old and real, and the town is still celebrated as a birthplace of Japanese soy sauce. The word shōyu itself was in use in Japan by the end of the sixteenth century.
Edo's appetite and the brewers of Noda
Soy sauce became a Japanese everyday seasoning in the Edo period. The growing city of Edo, now Tokyo, needed it in huge quantities, and breweries in Chōshi and Noda, in what is now Chiba, supplied it by river. Their sauce used more wheat than the western Japanese styles, which made it darker and more aromatic. It suited the city's food perfectly: the dipping sauce for soba, the glaze on grilled eel, and the new nigiri sushi, where chefs marinated tuna in soy to keep it. That preparation, zuke, survives in Zuke Maguro Nigiri and the rice bowl Zuke Don. Several Noda brewing families later merged, in 1917, into the company now known worldwide as Kikkoman.
Soy sauce reached Europe early, too. In the seventeenth century the Dutch East India Company, trading from its post at Nagasaki, shipped Japanese soy sauce in its cargoes to Asia and Europe. It was one of the first Asian flavours to reach European tables.
How soy sauce is brewed
A traditionally brewed soy sauce goes through four stages.
- Koji. Steamed soybeans are mixed with roasted, cracked wheat and dusted with spores of koji mould, a species of Aspergillus. Over a few days the mould grows through the mixture and fills it with enzymes.
- Moromi. The koji goes into salt brine to make a thick mash called moromi. For months, and sometimes years, enzymes break the proteins into savoury amino acids and the starches into sugars, while yeasts and lactic bacteria build aroma.
- Pressing. The mature mash is wrapped in cloth and pressed to release the raw sauce.
- Finishing. The sauce is gently heated, which sets its colour and aroma, then filtered and bottled. A few brewers still ferment in the old cedar barrels.
There is also a fast route. So-called non-brewed soy sauce is made in days, by breaking down soy protein with acid and then adding colour and flavouring. It is cheaper and tastes flatter and harsher. The label will tell you which one you're buying.
A guide to the bottles
| Type | What it is | Use it for |
|---|---|---|
| Koikuchi (Japanese dark) | The everyday Japanese soy sauce, brewed from roughly equal soybeans and wheat. It makes up the great majority of what Japan produces. | Almost everything: dipping, marinades, glazes, sushi. |
| Usukuchi (Japanese light) | Lighter in colour but saltier, a speciality of the Kansai region. | Clear broths and simmered vegetables, where you want colours to stay bright. |
| Tamari | Made mostly or entirely from soybeans, with little or no wheat. Thick, rich and deep. | Dipping, glazing, and sashimi. |
| Shiro (white) | Mostly wheat, very pale and sweetish. | Delicate dishes where colour matters. |
| Chinese light soy | Thin and salty, the main seasoning soy in Chinese cooking. | Stir-fries, dressings, dipping sauces. |
| Chinese dark soy | Aged longer and thicker, less salty, and often sweetened with molasses or caramel. | Colour and gloss in braises and red-cooked dishes. |
How to choose and use it
- Read the ingredients. A good bottle lists little more than water, soybeans, wheat and salt, and says "naturally brewed" or "traditionally brewed".
- Buy small bottles and refrigerate after opening. The salt keeps soy sauce safe, but air slowly darkens it and dulls the aroma.
- Taste before you pour. Brands vary a great deal in saltiness, so add a little, then taste.
- With sushi, go easy. Dip the fish side of nigiri, never the rice, which soaks it up and falls apart. At a good counter the chef has often seasoned each piece already with a brush of nikiri, a soy sauce softened with mirin and sake, and then you need no dipping at all.
The sauces chapter of The Art of Sushi shows how far the same bottle can go. There is Nikiri for brushing onto fish, citrusy Ponzu, and Tsume, the thick, sweet glaze for eel, alongside the classic Zuke Maguro Nigiri. For the shapes that go with them, see our beginner's guide to nigiri, maki and temaki, and use the recipe finder to find soy-seasoned dishes across all our books, Chinese braises included.
Questions people ask
Is soy sauce Chinese or Japanese?
It began in China, where fermented soybean pastes were made more than two thousand years ago. Japan developed its own styles, above all the wheat-rich koikuchi, which is the soy sauce most of the world now knows.
Is soy sauce gluten-free?
Usually not, because most soy sauce is brewed with wheat. Tamari is often made with little or no wheat, and some bottles are certified gluten-free, but always check the label.
What is the difference between light and dark soy sauce?
In Chinese cooking, light soy is thin and salty and used for seasoning. Dark soy is aged longer, thicker, sweeter and less salty, and it is used mainly to add colour. Japanese "light" usukuchi is a different thing: pale in colour but actually saltier than ordinary soy sauce.
Does soy sauce go off?
It is too salty to spoil easily, but it does lose quality once opened. Kept in the fridge, it stays at its best for a few months. If it has turned very dark and tastes flat, it is time for a new bottle.