What Is Soy Sauce?

Soy sauce in a bowl with a spoon

The Spruce

You're probably already familiar with soy sauce. This salty, umami-packed flavor bomb of a condiment has broken beyond the bounds of Asian cuisine to add an X factor of savoriness to everything from barbecue sauce to chili. Ever wondered what's in soy sauce? And if its sodium content should actually be a concern? Let's find out.

Summary of facts about soy sauce
The Spruce / Lindsay Kreighbaum

What Is Soy Sauce?

Soy sauce is a brown, salty liquid condiment made by fermenting soybeans or breaking them down with acid (hydrolyzing). This releases sugars as well as umami elements and develops the brown color for which soy sauce is known. Sometimes, in modern-day production, additional brown coloring is added. As wheat flour is commonly used in the process, those sensitive to gluten need to look for gluten-free and wheat-free versions, such as some types of Japanese tamari, which is typically a vegan product.

What Does It Taste Like?

Soy sauce provides salt, sweet, umami (savory), and even a little bitter flavor. This balanced flavor profile makes it an excellent condiment. You predominantly detect the salt, sweet, and umami, which mask the final bitter note. The free amino acids produced in hydrolyzation or fermentation combine to form natural monosodium glutamate (MSG), which is key to the umami taste.

How to Use It

Soy sauce can be used in a marinade or braising liquid for meat or added when cooking stews or soups. It's a basic way of building depth of flavor, is not affected by heat during cooking, and can provide a pleasing brown color to your dish. In stir-fries, it is usually mixed with the vegetables before including the noodles, but more soy sauce can be added at any time in the cooking process. Soy sauce can be offered as a condiment at the table, too, for additional salt and flavor as needed.

Soy Sauce Recipes

How Is Soy Sauce Made?

All cultures have a sauce that is used to stretch salt, which can be hard to obtain and very expensive in areas not adjacent to the sea. Soy sauce was created in China during the Han dynasty (206 BCE to 220 CE). Soybeans were boiled, wheat or barley was added, it was allowed to ferment, and then water and salt were added. Korea was soon using a similar process. It was also common for people to omit the wheat or barley altogether, making soy sauce traditionally a gluten-free product. (Today, most commercial soy sauces contain wheat.) Soy sauce was introduced to Japan by Chinese Buddhist monks around 600 CE, but it didn't make its way to Europe until the 1700s.

The technique of making soy sauce has changed over the years, going from a process that can take months to one that produces a finished product in a matter of days.

The traditional method for brewing soy sauce requires multiple steps and can take days to months to complete, depending on the recipe. Soybeans are first cooked to soften the bean, and then bacterial and fungal cultures are added to begin the fermentation process. Roasted wheat or other grains may also be included to provide a unique flavor.

The soybean culture mixture is then combined with a salt brine and allowed to “brew” for a specific amount of time. During this process, the microorganisms break down proteins and sugars that are naturally found in the soybeans into numerous compounds that create the complex flavor and color of soy sauce.

After the fermentation process, the mixture is pressed to extract the dark brown, flavorful liquid. (The resulting solids are often used as animal feed.) Before the extracted liquid is packaged and sold as soy sauce, it is pasteurized to eliminate harmful microorganisms and filtered to reduce particles and other debris.

Advancements in food production have led to a faster, less expensive method of producing soy sauce, which uses acid-hydrolyzed vegetable protein. This method only requires a few days and produces a more consistent product with a longer shelf life. Traditionalists reject this method, as it does not create the depth of flavor found with the traditional brewing method.

Soy Sauce Varieties

There are hundreds of varieties of soy sauce that are available on the market today. These varieties depend on the ingredients used, the method used to create the sauce, and the region in which it is made.

  • Light soy sauce is the thin, brown liquid that most Americans refer to as regular soy sauce. It is a good all-purpose seasoning and condiment and traditionally what is used when eating sushi.
  • Dark soy sauce has had molasses or caramel added after the brewing process, which thickens the sauce slightly and produces a sweeter, more complex flavor.
  • For people watching their salt intake, a low-sodium soy sauce may be the sauce of choice. Salt is an important component in the production of soy sauce because it acts as an antimicrobial agent. Most low-sodium soy sauces are made using the acid-hydrolyzed vegetable protein method, which does not utilize bacterial and fungal cultures and therefore requires less salt. 
  • Tamari is a Japanese soy sauce that is made with only soybeans and no wheat or other grains. Tamari has a very clean flavor and is favored by those who follow a wheat- or gluten-free diet.
  • White soy sauce, or Shiro Shoyu, is a traditional Japanese soy sauce that is lighter in flavor and color. Sporting an amber hue, it is popular with chefs when they want to add umami flavor to a dish without changing the color (as light or dark soy sauce would do). These signature characteristics are a result of the higher wheat-to-soy ratio.

Where to Buy Soy Sauce

Find light soy sauce in the supermarket in the Asian foods section or condiments section. Well-stocked markets should also have dark soy sauce and tamari. You can find traditionally fermented varieties at international grocers, along with lesser-known types, like white soy sauce.

Storage

Unopened soy sauce is shelf stable and can be kept in a cool, dark place for about three years. Once opened, however, soy sauce is best if used within three to six months as the flavor will deteriorate over time. While not required, it is perfectly acceptable to keep soy sauce in the refrigerator, as that can help maintain the flavor longer. Soy sauce won't spoil, but exposure to air will lead to oxidation and darken the sauce. This may also lead to a stronger flavor.

Is Soy Sauce Bad for You?

Soy sauce does contain high amounts of sodium, with leading brands containing roughly one-third of your daily recommended intake (DRI) of sodium per serving. However, low-sodium versions of leading brands can have just half of that, or 15 percent of your DRI. It's also been pointed out that 1 tablespoon of soy sauce has approximately one-tenth of the sodium as 1 tablespoon of salt, making it less salty by volume. Ultimately, it's up to you to be judicious with your salt intake and limit how much you use.

You may have also heard concerns about MSG, or monosodium glutamate. Glutamic acid (which MSG comes from) occurs naturally as a byproduct of the fermentation process. That being said, more MSG is sometimes added to commercial soy sauce to enhance the flavor.

But is it bad for you? The short answer is probably not. In fact, most people do not have an adverse reaction to MSG, as one 2016 study found. The study failed to find significant proof that MSG causes headaches, which are commonly thought to be an indicator of MSG sensitivity.

That said, others in the scientific community have raised concerns about other properties of commercially produced soy sauce. Because the modern production process has changed greatly, many contemporary brands rely on chemicals and additives to speed up or mimic the fermentation process.

Studies have found commercially produced soy sauce to be high in chloropropanols, which the European Union limits as a toxic substance in food products. According to a study published in Critical Reviews in Food Science and Nutrition, soy sauce can contain significant amounts of this type of compound. Note that traditionally fermented soy sauce does not contain these compounds, which are a result of modern food science, and not limited only to soy sauce production.

All this being said, it's good to keep in mind that soy sauce does include soy and sometimes wheat. So people with soy and wheat allergies (and of course, celiac disease, which is basically an intolerance to gluten, which is found in wheat) should look carefully at labels before consuming.

Substitutions

You may need a soy sauce substitute if you have simply run out of it and can't make a quick trip to the store. The umami element can be added using Worcestershire sauce, Maggi seasoning sauce, beef stock or bouillon, coconut aminos, or liquid aminos. You would need to adjust for the salt and sweetness usually provided by soy sauce as well.

One common need for substitution is for those on a low-sodium diet. A soy sauce substitute can be made using low-sodium beef broth, molasses, balsamic vinegar, red wine vinegar, sesame oil, garlic powder, and black pepper. This is simmered to reduce and concentrate it.

Article Sources
The Spruce Eats uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Obayashi Y, Nagamura Y. Does monosodium glutamate really cause headache? : a systematic review of human studiesJournal of Headache and Pain. 2016; 17:54. doi:10.1186/s10194-016-0639-4

  2. Jędrkiewicz R, Kupska M, Głowacz A, et al. 3-MCPD: A Worldwide Problem of Food ChemistryCrit Rev in Food Sci Nutr, 2016; 56(14): 2268-2277. doi:10.1080/10408398.2013.829414