What is Soy Sauce?

Soy sauce is a fermented condiment and seasoning sauce that plays a central role in Japanese culinary culture.

It is made primarily from soybeans, wheat and salt. A fermented liquid condiment and seasoning created through a fermentation process driven by microorganisms, soy sauce takes anywhere from half a year to three years per batch to make. There are around 1,200 soy sauce breweries throughout Japan, each making products with their own regional characteristics—soy sauces that are sweet tasting, or perhaps thick and rich instead, all rooted in local cultural traditions. Soy sauce is an indispensable condiment in Japanese cuisine, and it has many fans in countries around the world.

Soy Sauce Taste Characteristics

This highly versatile condiment brings out the full flavors of many different ingredients, offers tastes and aromas that further fuel the appetite, and even adds color to prepared dishes—it's rare to find an ingredient or food that doesn't go well with soy sauce. Soy sauce is used widely in Japanese cooking as well as Western cuisine, Chinese cuisine and others around the world. So what exactly makes soy sauce so versatile? There are two factors: its possession of all five tastes—umami, sweetness, saltiness, bitterness and sourness—and its more than 300 different aromatic variations. This combination of five taste characteristics and aromatic properties adds richness and depth to foods' flavors.

• Umami

  Brings Out Savory Flavor Depth

  The proteins contained in the soybeans and wheat are broken down through enzymatic reactions by koji mold (Aspergillus oryzae) and transformed into roughly 20 different varieties of amino acid to create the savory (umami) taste of soy sauce. Among these acids, glutamic acid plays the biggest role in creating umami taste.

• Sweetness

  Softens and Rounds Out Flavors

  The sweet tastes in soy sauce come from the conversion of wheat starch into glucose, galactose and other sugars during the fermentation process, and also from the sugar alcohol glycerol, the amino acids glycine and alanine, and other such sources.

• Saltiness

  Defines Flavor and Sharpens Focus

  Salinity concentrations of rich-tasting soy sauces are around 16%, and this saltiness helps define flavors, giving them a firmer focus. In contrast with table salt, which has a purely salty taste and nothing more, soy sauce provides a more delicious way to season foods, and it is for this reason that people of eras past used to refer to soy sauce as the "better-tasting salt."

• Sourness

  Mitigates Saltiness and Ties Together Flavor Characteristics

  Lactic acid, acetic acid, succinic acid and other organic acids—about nine in all—are present in roughly 1% quantities in soy sauce. These impart a slight sourness while mitigating salty flavors and making the overall flavor characteristics more unified and well-rounded.

• Bitterness

  Combines with Saltiness and Sourness for Richer Flavor

  Isoleucine and other amino acids, peptides, and other bitterness-imparting constituents are present in soy sauce. Rather than giving it a bitter taste, these elements combine with the salty and sour characteristics to produce greater flavor richness.

• Flavor

  Soy Sauce's Diverse Aromatic Properties

  The delicious flavor experienced when consuming soy sauce is due in large part to its aromatic properties. Fragrance constituents can include those of flowers, fruits, coffee and more—there are more than 300 possible types—all intricately intermixed.

Beneficial Effects of Soy Sauce

Soy sauce can make food more delicious by mitigating the strong smells of raw fish, adding color, and altering pH levels for better flavor. All of this is possible thanks to the microorganisms that create the sauce. Koji mold (Aspergillus oryzae), a type unique to Japan, miraculously triggers the yeast fermentation process to break down constituents in the soybeans and wheat over a three-month period and generate the product's taste and aromatic characteristics. Each of the constituents mutually effects the others to create balanced flavors and fragrances.

• Odor-eliminating Effect

  Removes Unpleasant Raw-ingredient Odors

  Sashimi is dipped in soy sauce before consumption not only to add flavor, but to get rid of any unpleasant raw fish odors—and it does this very effectively. In fact, soaking ingredients in soy sauce, known as shoyu arai, as part of the preparation process for some Japanese dishes is done for the exact same reason: to remove any unpleasant odors in raw fish, raw meat and other cooking ingredients.

• Heating Effects

  Generates Appetite-inducing Colors and Fragrances

  The aromas of kabayaki (fish broiled in soy sauce and other ingredients), yakitori grilled chicken skewers, and other dishes that tend to stimulate the appetite are rooted in aromatic substances created as the byproducts of amino carbonyl reactions, which are brought about by heating the amino acids in soy sauce as well as sugar constituents in sugar, mirin sweet cooking sake and other common cooking ingredients. The same reaction also gives food an attractive luster: dishes like teriyaki chicken (lit. "lustrous grilled chicken") makes use of this specific reaction in soy sauce.

• Bacteriostatic and Bactericidal Effects

  Sodium and Acid Constituents Help Food Keep Longer

  Because soy sauce contains salt content and organic acids, it stops the proliferation of, and even eliminates, E. coli bacteria. Foods are often marinated in soy sauce (shoyu-zuke), boiled down in soy sauce (tsukuda-ni), or otherwise prepared or treated in order to help them last longer.

• Flavor-contrasting Effect

  Brings Out Sweet Flavors

  Sweet-tasting boiled beans, for example, can have their sweetness enhanced further by adding a bit of soy sauce as a finishing touch. Soy sauce can also bring out the stronger of two primary flavors present simultaneously in a dish. In other words, it creates flavor contrasts.

• Flavor-reducing Effect

  Tones Down Excessive Saltiness

  Adding soy sauce can help reduce excessive saltiness in over-pickled foods, over-salted salmon dishes, and others that are too salty for one's tastes. This is due to the organic acids in soy sauce, which have the effect of toning down salty taste. To utilize this effect, one can mix it in with other ingredients to reduce the strength of one of both flavors.

• Synergistic Flavor Enhancement

  Interacts with Dashi Stock for Greater Savoriness

  Soy sauce's glutamic acid interacts with the inosinic acid in katsuo-bushi dried bonito shavings (used to create dashi cooking stock) to generate more umami taste. This is a synergistic effect, wherein mixing two ingredients makes both of their flavor impacts much stronger, and it is utilized to make dipping sauces for soba buckwheat noodles, tempura, and other dishes.

Soy Sauce Types

A wide variety of soy sauce types exist. The Japanese Ministry of Agriculture, Forestry and Fisheries (MAFF) classifies them under five categories established in the Japanese Agricultural Standards (JAS): shiro, white soy sauce; usukuchi, light soy sauce; koikuchi, dark soy sauce; saishikomi, twice-brewed soy sauce; and tamari, a traditional type of soy sauce. There is also a type not included in these categories called amakuchi, a sweeter-tasting variety made with additives such as sugars and sweeteners.

Umami in Soy Sauce

Soy sauce contains large amounts of free glutamic acid, which is the source of umami taste. We investigated free glutamic acid amounts—or umami levels—in well-known soy sauces from the five JAS categories and the amakuchi category. Please note that these values should only be used for general reference purposes, as umami amounts vary by individual soy sauce product.

Selecting the Right Soy Sauce

Balancing Color, Umami and Saltiness

The following chart compares soy sauces, with types to the left being lighter-colored and saltier, and types to the right being darker-colored and richer-tasting with more umami taste.
Many people who sample left-side soy sauces straight find them to be too salty and thus unappetizing, whereas the right-side sauces often to come across as better-tasting.

Bringing Out Ingredient Tastes vs. Adding Soy Sauce Flavor

Adding soy sauce to cooking ingredients and foods can change how they taste.
Lighter, saltier-tasting soy sauces bring out the delicious tastes of different things and can be used in much the same way as salt and lemon seasonings. These types are particularly good for whitefish, simmered dishes, soups and so forth.
However, the saltiness-centric taste of light soy sauce may produce a final result that feels lacking when used with steak, tuna sashimi and other such ingredients, in which case a richer-tasting, umami-rich soy sauce is better because it complements and blends well with the foods.

The History of Soy Sauce

Domestic Roots of Japanese Soy Sauce

The first instance of the word shoyu (soy sauce) in historical records dates back to the Azuchi-Momoyama Period (1573–1600). It appeared in the Ekirinbon Setsuyoshu, a dictionary of everyday Japanese words used at the time. However, products similar to soy sauce existed before that era, as did direct precursors in differing forms that would later evolve into the soy sauce we know and love today.

Origins of Shoyu: Uo-bishio, Shishi-bishio, Kusa-bishio and Koku-bishio

The practice of salting cereal grains apparently dates back to the Yayoi Period (300 BCE–300 CE). The Qimin Yaoshu, China's oldest extant agricultural text, describes related production methods, and the term hishio (the first character of shoyu, referring to a miso-like paste made from koji mold and saline water) is believed to have come to Japan during the Asuka Period (538–710). Hishio (often pronounced bishio when following another Japanese character) can be divided in three general categories: uo-bishio, which is used for salting fish; shishi-bishio, which is used for salting meat; and kusa-bishio, which is used for salting vegetables. Another type, koku-bishio, refers to the salting of grains, and this is the type believed to be the archetype for today's shoyu (soy sauce), miso, and other seasonings and condiments seen in Japan today.
In addition, one theory states that, after the Buddhist monk Shinchi Kakushin brought the production method for Kinzanji miso back from China during the Kamakura Period (1185–1333), producers found the liquid left at the bottom of the miso production vat to be delicious, and this liquid then served as the archetype for soy sauce in Japan. Additionally, one account names the town of Yuasa in Wakayama Prefecture as the birthplace of Japanese soy sauce.

Soy Sauce Spreads from West to East

Full-out, widespread soy sauce production began during the Edo Period (1600–1868). After the historic Battle of Sekigahara in 1600 and the transition into the Edo Period, the population of Edo (modern-day Tokyo) grew and the city developed rapidly. At the same time, it was heavily influenced by Kamigata (Kansai-area) culture. In 1726, approximately 76% of Edo's soy sauce was produced in Sakai, Osaka and other parts of Kansai and then shipped over; however, Kanto-area soy sauce production was growing with Chiba Prefecture as the main production center. According to one soy sauce wholesaler's 1821 report, only 20,000 barrels of the 1,250,000 barrels handled that year were from the Kansai area.

Nationwide Dissemination

Following this shift, producers began using water shipping routes along rivers such as the Edogawa and Tonegawa to transport soy sauce more quickly into Edo, and the area developed koikuchi (dark) soy sauce varieties in accordance with local tastes. Popular Japanese dishes such as tempura, kabayaki (fish broiled in soy sauce and other ingredients), and sushi were also established during this period in history, and soy sauce became a vital part of Japanese culinary culture.
In contrast to Kanto, usukuchi (light) soy sauces became the norm in Kansai-area production and consumption. Brewing one's own soy sauce at home was common in farming villages and persisted over the centuries, but starting in the Taisho Period (1912–26) the soy sauce was increasingly packaged in glass bottles, and from the Showa Period (1926–89) onward distribution networks were widely established and people in regular households throughout the nation began to purchase and use the product.

Becoming a Global Product

Soy sauce was first sold overseas during the Edo Period, shipped from the dedicated Dejima port in Nagasaki in accordance with the shogunate's sakoku ("closed country") policy which curtailed international trade and interactions severely. Records show that soy sauce was exported via Dutch trading ships to other parts of Asia as well as to Europe and other parts of the world. Even after Japan ended its sakoku policy and opened its borders for trade, export amounts remained small. However, numbers of emigrants from Japan grew during the Meiji Period (1868–1912), and following the First Sino-Japanese War (1894–95) and the Russo–Japanese War (1904–05) even greater numbers of Japanese citizens moved abroad after the establishment of Japanese bases of power in Korea, Sakhalin settlements, and Manchuria, China. In response, overseas demand for soy sauce rose further.
However, export amounts truly grew following the conclusion of World War II, spurred initially by demand from American supermarkets for tastings and sales of teriyaki chicken made using Kikkoman soy sauce (whose alluring roasted-type aromatic characteristics match well with the chicken). Members of the postwar Allied occupation forces in Japan were predominantly American, and during their time in Japan many such Americans were exposed to soy sauce and its usages. Upon returning to the United States, they helped encourage more widespread use of this condiment in their home country. Following sustained and patient efforts, in 1973 a local production facility was at last completed in the United States, in the State of Wisconsin. The pace of soy sauce internationalization continued to speed up, and today it is a common product in more than 100 different countries including Europe.

Soy Sauce Production Methods and Ingredients

Soybeans, Wheat and Salt as Main Ingredients

Soybeans, wheat and salt are the main ingredients used to make soy sauce. The proteins in the soybeans break down to release amino acids, which create the umami of the final product, while the wheat's starches break down to release glucose which imparts sweet flavor, aromatic properties and other characteristics. In addition to these, salt is also a vital ingredient, because it helps protect the brew from unwanted bacteria as it ferments over long time periods.
Another necessary ingredient—one which arguably plays the most important role in soy sauce fermentation—is koji mold (Aspergillus oryzae). Just like sake and miso brewers, most soy sauce brewers purchase their mold from specialized koji producers.

Standard Soy Sauce Production Process

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  1.The soybeans are steamed.

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  2.The wheat is roasted and crushed, then mixed in with the soybeans.

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  3.The koji mold fermentation starter is mixed in.

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  4.The koji is allowed to proliferate in a special room.

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  5.The moromi (fermenting mash) is created by adding saline water to the koji.

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  6.The mixture is moved to vats where it ferments and matures.

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  7.Press equipment is used to extract the soy sauce product.

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  8.The soy sauce is transferred to appropriate vessels.

Spreading the Word About Wooden-vat Production

Soy sauce produced using wooden vats accounts for less than 1% of all soy sauce made today.

Up through the Edo Period (1600–1868), basic Japanese seasoning and condiment products such as soy sauce, miso, vinegar, mirin sweet cooking sake, and sake were produced in wooden vats. However, the poor cost effectiveness of these vats caused a steady decline in use of this production approach, resulting in the current rate of less than 1% in the soy sauce industry today.
There is now only one company left making the large wooden vats used in this process. In order to prevent the complete extinction of wooden-vat brewing culture—a real possibility in today's brewing climate— it is important to draw attention to this cherished tradition. Young soy sauce brewers in particular have shown interest in adopting wooden-vat production, and new vats are being prepared in various parts of Japan today as breweries attempt to revive this traditional approach.

The Flavorful Benefits of Wooden-vat Production

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  Vats Are Breathing

  Japanese cedar is commonly used as a brewing vat material, and this wood's surface is filled with countless tiny holes which serve as homes to microorganisms, the main drivers of soy sauce fermentation.
  The vats also "breathe" as air passes through or water builds up, thus changing their appearance from day to day.

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  The Brewer's Personal Ecosystem

  Brewers can build up their own personal ecosystems using the microorganisms that live in the walls of wooden vats. In many cases, brewers who bring their wood vat materials to research centers for examination are able to discover new types of microorganic life. Long-standing breweries, often more than a century old, sometimes produce uniquely delicious flavors found nowhere else, and these little ecosystems are the ones to thank.

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  The Flavors of Long-brewed Soy Sauces

  Natural brewing via wooden-vat fermentation often spans the four seasons, bringing various temperature changes along the way. This natural approach requires at least a year to complete, and sometimes continues as long as three years for a batch. The result is a singular flavor only achievable through long brewing times— research has shown that this approach generates larger quantities of glutamic acid, which is a major umami constituent.

Wooden-vat Production Expert Revival Project

The Wooden-vat Production Expert Revival Project was launched in 2012, initiated based on calls to preserve wooden-vat brewing traditions by Yasuo Yamamoto, fifth-generation head of soy sauce brewery Yamaroku Shoyu. He began operating a wooden vat production business alongside his existing soy sauce business in order to ensure that wooden-vat production would still be around in the future for his children and grandchildren to experience and enjoy. To this end, Yamamoto along with Shodoshima Island carpenters Naoto Sakaguchi and Shin'ichi Miyake became apprentices at the wooden vat workshop Fujii Seiokesho in Sakai City, Osaka Prefecture.
Soy sauce produced using wooden vats accounts for about 1% of all soy sauce on the market. With the aim of working together toward the shared goal of enlarging the wooden-vat production market, rather than competing within that tiny market, brewers of soy sauce, sake and miso as well as distributors of these products and food traders are coming together in increasingly large numbers year by year.
Shodoshima Island hosts a wooden vat building event every year in January, and these brewers work together with event participants to build new vats. As the scope of these efforts expand, other producers in Japan are building their own wooden production vats as well.

Materials and photos provided: KIOKE