What is Shoyu? All About The Unique Japanese Soy Sauce

For many of us, our first encounter with soy sauce was in the context of Japanese food. It was likely sushi, with the side of ginger, wasabi, and a little bowl of soy sauce, there for the dipping. While those who know Asian cuisine even tangentially are aware that Japanese food doesn't have an exclusive right to soy sauce, the associations still hold many of us in an iron grip.

Maybe that's not so wrong, after all.

Have you ever noticed your Japanese-manufactured soy sauce tasting slightly different from Western or Chinese ones? Some ascribe that difference in taste to quality, and while it's undoubtedly true that premium-quality Japanese soy sauce is worth every penny, the truth is a little more complicated.

To put it very succinctly: Japanese-style soy sauce is called Shoyu. Shoyu and Chinese-style soy sauce differ in taste because the recipe for Japanese-style soy sauce differs in several important ways from the Chinese-style soy sauce, which we've come to know as the regular one. 

What is Shoyu?

Shoyu is a term exclusively used to refer to Japanese-style soy sauces. The main ingredients of shoyu sauce are fermented soybeans and wheat (usually used at a ratio of 1:1), water, and some sea salt to act as a preservative. This is the stripped-down, basic recipe for shoyu soy sauce. 

More often than not, the wheat used for shoyu sauce is toasted to add more complex flavor undertones to the final product. Commercial manufacturers also tend to expand upon it by adding ingredients such as vinegar, mirin (low-alcohol rice wine often used as a flavoring element in Japanese cooking), different sweeteners, etc.

Most shoyu recipes also utilize Koji, a type of filamentous fungus widely used for rice and barley saccharification purposes in alcohol (sake, for example) and soybean fermentation (like in miso paste). However, in some instances, Koji may be substituted with other mold cultures (though, for fairness' sake, this isn't very common).

But more often than not, shoyu sauce is made with a 50/50 soybean and wheat, water, and sea salt, without further amplification. What gives it its distinct flavor is the fermentation process that lasts for a minimum of six months and can last up to two years. 

How is Shoyu Different from Regular Soy Sauce?

What we tend to refer to as soy sauce on the regular is, most often, jiàng yóu, or Chinese-style soy sauce. The term is used interchangeably and without specification, because it's the world's most common soy sauce variety. 

Like Japanese shoyu soy sauce, Chinese-style soy sauces are also made by combining fermented soybeans, grains (typically wheat), and some preservatives. There are a few critical differences in the recipe, though.

First of all, the soybean to wheat ratio isn't as carefully guarded. Chinese-style soy sauce tends to contain significantly more soybeans, with the ratio to wheat usually ranging between 70:30 to 80:20. The wheat used in Chinese-style soy sauces is regular wheat flour.

That's the more high-end, gourmet Chinese soy sauce.

The cheaper versions are usually made with hydrolyzed soy protein or through some kind of chemical process to accelerate the production and minimize the costs. They're also not fermented for nearly as long as Shoyu soy sauce. More high-end stuff can be left alone to ferment for a few months (typically 5 to 8), but more often than not, Chinese soy sauces are only fermented for a few weeks, maybe up to a month.

Here at Yummy Bazaar, we keep a wide selection of gourmet Japanese sauces, including various shoyu sauces. If you decide you want to find out how these differences in recipes affect the flavors, of course.

How is Shoyu Made?

The first step is to get soybeans and wheat ready. Soybeans need to be steamed, and wheat needs to be toasted and crushed before they can be combined. Once the main ingredients are prepared and mixed, the chosen mold (usually Koji) is added to prepare the mixture for fermentation.

The soybean-wheat-mold mixture needs to be kept separately for a few days so that the (Koji) mold can spread and cover the mixture's surface. The mold is necessary for the fermentation process since it contains different enzymes that contribute to breaking down other elements in the mix. Due to mold enzymes, proteins, lipids, fatty acids, starch, and cellulose are all broken down through the maturation process.

Once Koji mold has sufficiently spread, the matured mixture is combined with salt water (sea salt is preferable). This new blend is called Moromi. 

Moromi is left in fermentation tanks for a period of at least six months, which is a minimum for Shoyu sauce, but the process can last over three years. The longer moromi is left to ferment, the more intense and complex the final shoyu sauce flavor.

After the moromi blend has matured, it's wrapped in cloth and compressed to extract raw soy sauce. The raw liquid is then heat-treated to remove harmful bacteria, refined, and finally bottled to be sold.

Are There Other Types of Japanese Soy Sauces?

Classic shoyu soy sauce can be separated into two varieties: koikuchi and usukuchi.

Koikuchi shoyu is the dark soy sauce and is considered to be the standard, all-purpose soy sauce. You're unlikely to encounter koikuchi on most shoyu sauce labels, as it's assumed by default that unlabeled shoyu is koikuchi. It's widely used in Japanese cuisine, both for cooking and dipping. When the recipe doesn't specify the kind of shoyu you need to use, then it's automatically calling for koikuchi.

It has a very deep and strong umami flavor, is moderately salty, and has distinct sweet undertones. Usukuchi shoyu is a light soy sauce. It may be paler in color, but the taste is, if anything, more intense. Like koikuchi, usukuchi has a deep umami flavor but is on the saltier side, and sweet undertones are almost undetectable. It's often used for seasoning, especially when the Chef wants to avoid darkening the dishes' color (sometimes replacing the salt), and as an ingredient in sauces and marinades, but it isn't usually used for dipping on its own.

Other than these two, there are also several non-classic Japanese soy sauce varieties:

Tamari soy sauce, also called Tamari shoyu, is probably the most well-known aside from classic shoyu. What sets tamari soy sauce apart is that it's made entirely out of fermented soybeans without wheat (or any other grain). Thus, tamari soy sauce is 100% gluten-free. 

Some, who prefer using Tamari soy sauce to classic shoyu sauce, claim that it has a richer, more well-balanced flavor, though that can be up to debate. Most untrained chefs indeed fail to see much difference since tamari soy sauce is often used as a gluten-free substitute for shoyu without altering any other elements of the dish to compensate for the flavor change. Tamari soy sauce may sometimes be a little thicker in consistency.

Saishikomi shoyu literally means "re-brewed soy sauce." This type of shoyu soy sauce is double-fermented by having water and brine removed during the second stage of fermentation. To describe very crudely, the final product contains double the soybean and wheat amount per the same amount of water and salt as regular koikuchi shoyu. Saishikomi shoyu sauce has a darker color and thicker consistency, with a more intense umami flavor and more aromatic sweet undertones. Saishikomi shoyu isn't usually used for cooking, but as a dipping sauce, especially for raw or slightly cooked ingredients, like sashimi and tataki. Due to this, saishikomi shoyu is sometimes labeled as sashimi shoyu sauce, like the one from Higashimaru.

Shiro shoyu differs from the classic shoyu due to its higher wheat content. The ratio of wheat to soybeans in Shiro shoyu is around 80:20. Its color ranges from almost translucent to pale amber. Due to its shorter fermentation period (Shiro shoyu is typically fermented for about four and no more than six months), the taste is very delicate, significantly milder, and less salty than classic shoyu sauce, but with noticeable umami notes. It's often used as a seasoning for dishes made with mild ingredients as classic shoyu may overpower them or when chefs want to preserve bright and vibrant colors for the dishes' visual appeal. 

How is Shoyu Sauce Used?

Shoyu is undoubtedly the most popular among Japanese sauces. Frankly speaking, the trouble would be finding a recipe that doesn't use soy sauce in some capacity, not the other way around. 

The most common ways to use shoyu soy sauce is as a seasoning or a dipping sauce, particularly the classic koikuchi variety (though tamari soy sauce is frequently used for these purposes, too). Shoyu is often used to flavor soup and stew bases, sometimes simply to amplify the umami flavor, sometimes with shoyu itself as the star of the show. Shoyu ramen, for example, is a famous noodle soup, with the broth's intense shoyu being the main point of attraction.

Classic shoyu sauce, especially a more high-grade one, is considered to be a great dipping sauce all on its own, often accompanying sushi and gyoza at eating establishments. Shoyu can also serve as a base for other widely used sauces, like ponzu and teriyaki. 

Or, to be more exact, ponzu sauce on its own is simply a colorless liquid made from citrus, but it's most often used as ponzu shoyu, a mixture with soy sauce. Though, when one mentions ponzu sauce, it's usually understood that they mean ponzu shoyu. 

Teriyaki sauce is, in reality, called tare, while teriyaki refers to the cooking technique when tare-glazed food is broiled or grilled. Tare is a very sweet shoyu-based sauce that requires koikuchi shoyu to be mixed with sake and a sweetener, most often sugar. Sake can sometimes be substituted with mirin, while sugar can be substituted with honey.

Usukuchi shoyu, as mentioned above, is seldom used for dipping but is frequently used for seasoning, sometimes instead of salt. It works best for light broths with intense flavors and stir-fries. 

Tare isn't the only type of glaze that uses shoyu (though it's the most popular). Usukuchi (light shoyu sauce) is frequently used for glazes, simmered with sugar and pepper, and sometimes with sake as well. This type of glaze works particularly well with poultry and fish with less intense flavors.

Marinades or marinade blends are another popular way to use shoyu sauce. It can be used on its own to marinade almost anything: eggs, fish, chicken, port, etc. Koikuchi shoyu is, once again, the most popular option for marinades on its own, but tamari and usukuchi sauces are frequently used as well. The latter works exceptionally well in marinade blends with other seasonings and flavoring ingredients due to its intense flavor, which cannot be easily overpowered. 

Pickling is another popular way to use shoyu sauce. Shiro shoyu is considered to be one of the best options for pickling as it doesn't alter the colors and the ingredients maintain vibrant colors. Due to its mellow flavor, Shiro shoyu is considered to be an excellent option for seasoning seafood, particularly shrimp and scallops. 

Saishikomi shoyu is the most limited one when it comes to uses. Theoretically, you can use it as a seasoning in moderate amounts, but its primary purpose is still to serve as a dipping sauce, not a flavoring agent. 

Can Shoyu Be Substituted with Regular Soy Sauce?

We've waxed poetic about the differences between shoyu soy sauce and regular Chinese-style soy sauce, but they're still similar products. It means you can use traditional soy sauce for cooking Japanese recipes, especially if you go a few steps further to make up for differences in flavor profiles.

The easiest way to do this is to add a dash of MSG (monosodium glutamate) to your dish. MSG is basically umami in powder form, so a small amount will compensate for the differences in soy sauce flavor profiles. 

You can also add a pinch or two of sugar to your cooking to imitate the subtle sweet undertones shoyu brings to the dishes, but don't overdo it.

Are There Other Alternatives for Shoyu?

If you don't fair well with either soy or gluten, another possible substitute for shoyu sauce would be liquid aminos. Liquid aminos are made by breaking down soy protein into free amino acids using a type of acidic chemical solution.

Liquid aminos taste more mellow and less salty than standard soy sauce. Still, they have noticeable sweet undertones, making them a suitable alternative to shoyu if you're looking for a soy-free and gluten-free option.

How Long Does Shoyu Last?

Shoyu and tamari soy sauces are naturally brewed and fermented, meaning they have less shelf life than regular soy sauces. When hermetically sealed, they can last up to two years, but once open, they should be used up in about three months.

As with most condiments, shoyu is labeled with the "best by" date, not an expiration date. If you pass it, the sauce will not likely make you ill. It will, however, start changing color and consistency, becoming darker, and developing a more intense flavor (at the expense of complexities) due to the oxidization process.

The one health risk lies in mold development. You can use shoyu soy sauce if it's past the best-by date, but if you notice it has developed mold, immediately discard it.

How to Store Shoyu to Prolong its Shelf Life:

Shoyu bottles should be sealed when not being used to avoid contamination, particularly by water. The manufacturer of the most popular shoyu sauce in the world, Kikkoman, claims that it'll last fine for a few months at room temperature. 

The problem is that it will degrade fast in the heat, so if the temperature in your kitchen isn't constantly controlled, storing it in the fridge might be the best option to prolong its flavor, even if it isn't strictly necessary.