What exactly is soy sauce?
Soy sauce is a salty, umami liquid made from fermented soybeans. At a minimum, it is made with soybeans, salt, and fermented with a mold—typically Aspergillus oryzae—known in Japanese as koji.
In the 20th century the production of soy sauce was modernized. Today most soy sauce is made in giant batches at automated factories. Instead of whole soy- beans, it is often made with acid-hydrolyzed soy protein—a processed, ground up soybean product. (This is what’s in the plastic packets of soy sauce handed out at many restaurants. It’s also what’s in a bottle of “liquid aminos.”) The modernizations produce soy sauce much more cheaply and quickly, reducing the time needed to ferment the sauce from years to months or even days. It also strips away the subtleties and depth of flavor that distinguish great traditional soy sauce.
What distinguishes traditional Japanese soy sauces from others?
In addition to the standard soybeans, salt, and koji, Japanese soy sauce—called shoyu in Japan—is typically also made with wheat and water. The wheat adds a subtle sweetness to the sauce, and helps to kickstart the fermentation.
Shoyu generally doesn’t contain other flavorings—or if it does, it’s called by another name, like ponzu, a soy sauce with citrus. Soy sauces from other countries often contain a whole range of additional ingredients, from mushrooms to fish to palm sugar to licorice to pineapple. Traditionally, Japanese soy sauce has been fermented in enormous cedar barrels called kioke, each about five feet across and eight feet deep. These barrels hold batch after batch of soy sauce and are often in use for decades. Rather than imparting a woody flavor, they help propagate microbes from one batch of soy sauce to the next, much like how the pine boards in a cheese aging room contribute to the flavor of the cheeses. Today, only 26 soy sauce makers in Japan still use kioke; 99% of soy sauce is aged in humongous steel or concrete tanks.
How is Japanese soy sauce made?
First, steamed soybeans and crushed wheat are inoculated with koji. The koji provides much of the flavor for the finished sauce, just as cultures do for cheese. After allowing the koji to bloom for a few days, the soybeans and wheat are transferred to kioke or tanks and mixed with salt water brine. The mixture ferments for months or years, getting stirred frequently to keep the aerobic microbes active. After the fermentation is complete, the wet soybean paste is slowly pressed, squeezing out the soy sauce over hours or days. Then it’s bottled and ready to sell.
There are five main types of Japanese soy sauce
- Shiro — white soy sauce. Shiro is more delicate in flavor and a good choice for adding a subtle umami kick to most dishes.
- Usukuchi — light soy sauce. Usukuchi is the saltiest and best used as a seasoning while cooking.
- Koikuchi — dark soy sauce. Koikuchi is the classic salty, savory soy sauce used for dips, stir fries, sauces, and more.
- Saishikomi — double brewed soy sauce. Saishikomi has a rounder, less salty flavor so it’s great as a finishing touch on dishes.
- Tamari – complex umami flavor with a lingering finish. Use tamari as a dipping sauce or as a glaze.
About 80% of the soy sauce used in Japan is koikuchi— dark soy sauce. This is the sauce you’ll find on tables at restaurants and in nearly every home.
How does Japanese soy sauce compare to Chinese soy sauce?
While Japanese soy sauces are neatly categorized, Chinese soy sauce has many more variations, and is called by many different names in different dialects across the country. In the US, many of the earliest Chinese immigrants came from the province of Guangdong (formerly Canton), so what we think of as “Chinese soy sauce” typically stems from Cantonese traditions. There, the common soy sauces are light and dark. If a Chinese-American recipe does not specify which soy sauce to use, light Chinese soy sauce is the standard.
Chinese light and dark soy sauces are not equivalent to Japanese light and dark sauces. If a Chinese recipe calls for light soy sauce, Japanese dark soy sauce is a good substitute. Chinese dark soy sauce is generally thicker and sweeter due to the addition of sugar or molasses. There isn’t a good Japanese equivalent.