Shoyu - Curiosities about Soy Sauce

Shoyu (醤油) is one of the most important condiments in Japanese cuisine. The dark, salty sauce with a deep umami aroma shows up next to sushi, sashimi, teriyaki, dashi and countless other dishes. If you eat in Japan, you cannot avoid it — and outside Japan, shoyu keeps turning up in more and more recipes.

In this article we look at where shoyu comes from, what varieties exist, how it is traditionally brewed, and how you can use it well in your own kitchen. One small warning first: if you watch your sodium, you will want to handle shoyu with care.

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What is Shoyu?

Shoyu simply means "soy sauce" in Japanese, written 醤油. The two kanji are made of 醤, which evokes a paste or puree (related to miso), and 油, which means oil or liquid. In Chinese the same characters are used, but the word is pronounced jiàngyóu (酱油).

The origins of shoyu lie in China, where it is documented around the year 500 AD. In Japan the sauce appears in written records from roughly the 7th century. That is no accident: long before shoyu, people in Japan fermented meat, fish and vegetables into pastes and sauces to preserve and season food. One of those pastes was the ancestor of miso, and from it came tamari — the shoyu variety you still find on the table next to sushi and sashimi today.

Types of Shoyu

Stand in front of the shelf at a Japanese supermarket and you quickly notice: there is no single shoyu. The main varieties are:

Koikuchi Shoyu

The dark, everyday standard. Koikuchi (濃口) literally means "thick flavor" and accounts for around 80 percent of Japanese production. It is salty, slightly sweet and rich in umami. Koikuchi works in almost anything, from soups to marinades to stir-fried vegetables.

Usukuchi Shoyu

Usukuchi (淡口) literally means "light flavor" and comes from the Kansai region, especially Kyoto. The color is lighter than koikuchi, while the salt content is about 10 percent higher. That lets it season more strongly without darkening the dish — perfect for clear soups, dashi-based dishes and delicate white vegetables.

Tamari

Tamari (たまり) is the oldest form: a thicker, almost wheat-free soy sauce that drains off as a by-product of miso production. Tamari tastes richer, with less sharpness in the nose, and pairs especially well with sushi, sashimi and as a base for teriyaki. For people with gluten sensitivity, tamari is often the safer choice.

Saishikomi

Saishikomi (再仕込) means "twice brewed." Instead of being set with ordinary brine, this sauce is set with already finished koikuchi shoyu. The result is dark, very aromatic and unusually intense. Saishikomi shows up with sushi, sashimi and tofu dishes when you want an extra-deep flavor.

Shiro Shoyu

Shiro (白) means "white" and is the pale exception among shoyu varieties. It is brewed with noticeably more wheat than soy, and tastes milder, sweeter and almost nutty. Shiro is used mostly in clear soups and with delicate white fish, when you want the color of the dish to stay clean.

How is Shoyu Made?

A real, traditionally brewed soy sauce is not just soy. The base is four ingredients: soybeans, roasted and ground wheat, water and salt. On top of that comes koji (Aspergillus oryzae or related strains) — a mold that converts starch into sugar and gets the fermentation going.

The rough flow looks like this. The soybeans are soaked, steamed and mixed with the roasted wheat. Koji spores are inoculated onto the mix, which ferments under controlled conditions and ripens into a koji mash. That mash is stirred with brine to form the moromi (醪), which then ages in wooden vats or modern tanks for six months to two years. At the end, the moromi is pressed, filtered and briefly pasteurized so the sauce keeps.

Because demand is so high, there is also a fast, chemical process. In about a week, soy proteins are hydrolyzed with hydrochloric acid, colored with caramel and spiked with flavorings. These sauces often carry labels like "quickly brewed" or "hydrolyzed." In taste they sit well below a real, fermented soy sauce, but they are cheap and very long-lasting. Once you have tried genuine shoyu, you taste the difference immediately.

Culinary Uses

Shoyu replaces salt in everyday cooking and, on top of that, brings color, aroma and umami. In Asian cuisine the sauce ends up in almost every recipe, even in sweets like dango or in caramel for desserts. In Japan itself, though, the dosing is much more restrained than you might expect.

Against the common image, shoyu in Japan is rarely poured in large amounts over the finished dish. With sushi and sashimi, you dip the fish lightly into the sauce and the rice stays as dry as possible. In soups like miso shiru or shoyu ramen, shoyu goes into the broth, not on the spoon. In restaurants, shoyu is always on the table so you can adjust the seasoning yourself at the end.

A few classic uses at a glance:

• Teriyaki — shoyu, mirin, sake and a little sugar make the classic glaze for chicken, salmon or tofu.
• Sushi and sashimi — tamari or koikuchi as a dip for the fish, without soaking the rice.
• Dashi-based soups — usukuchi or koikuchi as a salt replacement in miso shiru, suimono or ramen broths.
• Rice dishes — oyakodon, donburi or takikomi gohan all gain depth from a splash of shoyu.
• Salad dressings — goma-ae and other vegetable sides are seasoned with shoyu, sesame and a little sugar.

If you want to dig deeper into Japanese food culture, take a look at our list of popular Japanese dishes in anime and our overview of the different types of sushi and maki.

Health Aspects

Shoyu has a high sodium content, and that is both its biggest plus and its biggest minus. A common guideline: 1 to 2 tablespoons a day is reasonable for most adults; more than that quickly shows up in blood pressure for people sensitive to salt. In large amounts over soups or rice, you are usually better off holding back — especially if your diet is already heavy on salty products.

At the same time, shoyu as a soy product also delivers things the body responds well to: plant protein, iron, calcium, B vitamins and secondary plant compounds with antioxidant effect. Epidemiological studies from Asia link moderate soy consumption to a lower risk of osteoporosis and certain cancers. That is not a free pass to drink shoyu by the liter, but it does show that, as usual, the dose is what matters.

If you want to play it safe, look for naturally brewed products with soy, wheat, salt and water on the label — and as short an ingredient list as possible. Cheap industrial sauces with hydrolyzed protein, corn syrup and artificial flavors fall short on both taste and nutrition.

Closing

Shoyu is more than a salty sauce. The centuries-old fermentation with koji, the four basic ingredients and the range of varieties make shoyu one of the most interesting condiments in the world. Try it properly for the first time — a good koikuchi from an Asian grocery, a few drops over white fish or into a clear dashi soup — and you will quickly understand why the sauce plays such a large role in Japan.

Try out the different varieties, line up tamari, usukuchi and koikuchi side by side, and see which one fits your palate. Shoyu rewards curiosity — and you will not want to miss it in your own kitchen again.