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.
About “Shokunin Shoyu”
The Shokunin Shoyu website sells select soy sauce brands from all around Japan in uniform 100-milliliter (3.4-ounce) bottles. Shokunin Shoyu's Mantaro Takahashi, who wrote the Shoyu Hon ("Soy Sauce Book"), has personally visited over 400 different breweries in Japan, and he strives to make his organization into a presence that effectively connects traditional and locally-based soy sauce makers with product users. If you are interested in trying some of the diverse range of different soy sauces available, we recommend visiting their website Shokunin Shoyu. Please note that the website is only available in Japanese.
Reference: Shoyu Hon ("Soy Sauce Book") Written by Mantaro Takahashi / Keiko Kuroshima / Published by: Genkosha
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.
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.
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.
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."
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.
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.
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.
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.
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.
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.
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.
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.
Shiro (White) Soy Sauce
This amber-tinted variety is the most light-colored of the soy sauces. Wheat is its main ingredient, and it is fermented and matured for a shorter time. Because the resulting soy sauce has less umami (savoriness) than other types, it is used to bring out the flavors of cooking ingredients.
Shiro soy sauce doesn't change the color of dishes, making it useful as a condiment for rice with beans mixed in (mame-gohan), as a seasoning when cooking meat for fritters, and in other such applications. Small amounts of shiro soy sauce can be used instead of salt in order to preserve the tastes of original ingredients.
Approx. salt content:17～18％
Usukuchi (Light) Soy Sauce
This light soy sauce is widely used in Western Japan. It is useful for simmered dishes, soups, and other culinary selections where the colors and dashi stock are meant to be brought to the fore.
Despite its light coloring, usukuchi soy sauce is high in sodium content; compared with koikuchi, just a small amount of usukuchi can be used to deliver sufficiently salty taste. This variety is good for bringing out the inherent flavors of ingredients, so in addition to imparting a lovely color to dishes it can be used for a bit of flavor in place of salt, lemon and other such enhancers.
Approx. salt content:18～19％
Koikuchi (Dark) Soy Sauce
The most common type of soy sauce in Japan, koikuchi accounts for 80% of all soy sauces on the market, and it is by far the dominant type in Eastern Japan. Koikuchi adds an elegant reddish-brown coloring to raw and fresh ingredients. It is produced all throughout the nation, from Hokkaido in the north to Okinawa in the south. A truly versatile soy sauce, its uses range from a dipping-sauce condiment to a seasoning for various dishes.
However, be aware that koikuchi oxidizes with time after opening, making its color go darker.
Approx. salt content:16～17％
Saishikomi (Twice-Brewed) Soy Sauce
This rich-tasting soy sauce has a long fermentation and maturation period. Saishikomi soy sauce is actually brewed in another finished soy sauce product, meaning it requires twice the ingredients and twice brewing time of koikuchi varieties. Featuring good flavor and aromatic balance, saishikomi goes very well with sashimi, and it can also be used in place of sauces for deep-fried foods, meat dishes and the like. Also, try adding it as a secret ingredient to some of your favorite dishes, or splashing a bit on top of simmered foods for a bit of extra umami.
Approx. salt content:12～14％
Tamari Traditional Soy Sauce
Tamari soy sauce uses soybeans as its primary ingredient and is made with less water, resulting in a flavor packed with umami taste. Its fermentation period is long, resulting in a darker appearance and unique aromatic properties. The tamari variety features some of the highest umami levels of all soy sauce types, making it popular as a dipping sauce (no other flavor additions needed), and also as a teriyaki sauce with excellent lustrous properties. Some tamari soy sauces are produced without any wheat at all, which has made them increasingly popular among both Japanese and non-Japanese users on gluten-free diets.
Approx. salt content:16～17％
Flavors of Specific Regions
Amakuchi (Sweet) Soy Sauce
A standard type of soy sauce in Kyushu, Hokuriku and certain other parts of Japan, amakuchi soy sauces have deep roots in their respective regions. They tend to get sweeter the closer their production site is the seacoast, and some regions' amakuchi are shockingly sweet to the unaccustomed consumer. This soy sauce type is often preferred for food such as grilled rice balls and raw egg over rice, not to mention whitefish-type sashimi.
MAFF has no official JAS definition for amakuchi soy sauce. Koikuchi is made using one of three different production methods: honjozo (traditional fermentation), kongo (mixing), and kongo-jozo (mixed fermentation). Among these, kongo and kongo-jozo produced soy sauces are considered to be amakuchi. These two methods use amino acid liquid in the production processes and are seen often in Kyushu, Hokuriku and certain other parts of Japan. The amino acid liquid itself does not possess sweet flavor, so sweeteners are often used as well to add sweet taste.
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.
Soy Sauces Used for Umami Substance Analysis (mg/100 g)
Yuki Shiro Shoyu (Shiro Soy Sauce)
Nanafuku Jozo (Hekinan City, Aichi Prefecture)
Nanafuku Jozo was the first brewery in Japan to produce shiro dashi stock. This organic shiro soy sauce is impressive, made with only the most carefully selected ingredients and numerous environmental considerations taken at the production facility. Visitors can take tours of the brewery, which goes by the name Arigato no Sato (Thank You Village).
Tatsuno Honzukuri (Usukuchi Soy Sauce)
Suehiro Shoyu (Tatsuno City, Hyogo Prefecture)
Usukuchi soy sauce goes well with any type of ingredient or food. Its mild salty taste and overall flavor make it useful for bringing out the inherent flavors of ingredients when used in cooking—the originally intended purpose of usukuchi varieties. In addition, it can be added on foods in place of seasonings such as salt and lemon.
Sashimi Shoyu (Amakuchi Soy Sauce)
Kubo Jozo (Kanoya City, Kagoshima Prefecture)
This soy sauce boasts a sweeter taste and thicker texture than any other brand made in Kagoshima. A thick soy sauce—a characteristic of Kagoshima soy sauces in general—this variety offers umami taste and rich flavor amidst bold sweetness. Despite its heavy overall feel, this soy sauce is an amakuchi. In addition to its use as a sashimi dipping sauce, Sashimi Shoyu is useful for cooking as well.
Byakuju (Koikuchi Soy Sauce)
Ishimago Honten (Yuzawa City, Akita Prefecture)
This brewery preserves traditional brewing methods to an extent that would surprise even the most seasoned soy sauce producers. Byakuju is a highly versatile soy sauce that goes well with anything, making for a lot of repeat customers. It is characterized by its unique aroma and tastes great with piping-hot buttered potatoes.
Soy sauce fermented and matured for approximately two years is returned to the vat and brewed again in finished soy sauce (saishikomi) for an additional two years. It is produced in this way to achieve most deep-reaching, rich yet well-rounded flavor possible. This soy sauce goes well with vanilla ice cream and sashimi, and can also be mixed with wasabi for use as a meat flavoring.
Owari no Tamari (Tamari Soy Sauce)
Marumata Shoten (Taketoyo-cho, Aichi Prefecture)
A gluten-free, rich-tasting tamari soy sauce made using unprocessed soybeans and salt, and fermented and matured in cedar vats over a three-year period. It is characterized by its concentrated soybean savoriness, thick texture and rich flavor. Owari no Tamari tastes good with sashimi and is useful in cooking as well.
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.
Food and Soy Sauce Compatibility
Koikuchi soy sauce works well with high-quality meats one might normally season with rock salt. In addition to salty taste, a bit of umami from the soy sauce is added to the overall flavor. This is the perfect way to bring out the inherent meaty flavors.
Saishikomi can be mixed with wasabi or blended with butter, garlic or similar. This adds a strong soy sauce presence while enhancing the meat's taste.
Rich-tasting tamari isn't overpowered by the fatty, umami-rich flavors of the meat. Heating this soy sauce strengthens its aromatic properties and luster. We recommend trying the simple seasoning combination of black pepper and tamari soy sauce.
Use usukuchi soy sauce with soft kinu tofu to get a similar effect as seasoning the tofu simply with salt. Soy sauces with saltier tastes greatly enhance the sweet flavor of the tofu.
Use saishikomi with bold-flavored, firm momen tofu varieties. This soy sauce type has enough umami to prevent it from being overpowered by the momen tofu's flavor, and it ties the overall dish together with well-rounded flavor.
Tamari goes well with standard-type momen firm tofu. The rich umami characteristics of the soy sauce envelop the tofu's flavor, giving it a taste that one might even describe as sweet.
Shiro pairs well with whitefish sashimi, scallops, northern shrimp and other delicately flavored foods on which one might normally use lemon, olive oil or similar.
Versatile koikuchi goes well with any type of sashimi. There's nothing quite like fresh, raw seafood flavored with freshly brewed soy sauce!
We highly recommend saishikomi soy sauce for tuna sashimi, as it eliminates any fishy odors and brings out the inherent taste.
Tamari is great for fatty-fish sashimi, as the well-rounded flavor of the soy sauce complements the sashimi well. This soy sauce can also be blended with mirin sweet cooking sake for use as a flavoring broth.
Usukuchi is best when using high-quality egg on the rice. The soy sauce's flavor is gentle, thus centering the flavor focus firmly on the egg.
Koikuchi is the standard type of soy sauce used for this dish. Even when additional toppings are added alongside it, koikuchi keeps the overall flavor balanced.
The rich, well-rounded taste of tamari soy sauce blends well with the egg's flavor so both can be enjoyed as one. This is the optimal pairing for those who prefer a pronounced soy sauce flavor, or else like bold flavors in general.
Shiro soy sauce is good for rice cooked with beans, corn or other vegetables added in for color. The gentle saltiness helps bring out the sweetness of the ingredients.
Usukuchi adds only faint coloring to the dish along with just a bit of soy sauce umami. Give this combination a try!
Its firm color and aromatic properties make koikuchi a good paring with these dishes—and even scorched-rice varieties! Koikuchi is also great for rice cooked with a large amounts of ingredients mixed in.
Although the combination of ice cream and soy sauce may seem unconventional, adding soy sauce actually creates a flavor profile not dissimilar to that of caramel toppings or the sauce on mitarashi dango (rice dumplings with sweet soy sauce glaze).
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.
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.
The soybeans used to make soy sauce come in two types: unprocessed soybeans and defatted soybeans, the latter of which accounts for more than 80% of all soybeans used in market production. Defatted soybeans do not contain much oil, which means their umami amount is high. Their constituents also break down and elute quickly.
Wheat starch breaks down into glucose to give soy sauce its sweet flavor and aromatic properties, among other characteristics. Broadly speaking, wheat primarily serves as the source of aromatic properties in soy sauces; however, it also has proteins which break down to form the amino acids that impart umami. In fact, about 25% of soy sauce's umami comes from the wheat.
Salty taste is an integral part of soy sauce's overall flavor. Furthermore, salt protects the product from unwanted bacteria during the long fermenting and maturation periods required for its production. Solar salt from other countries such as Mexico and Australia is often used in soy sauce production.
Koji mold is used as a fermentation starter which is added in to the mix of steamed soybeans and roasted wheat. The proliferation process of this starter generates enzymes, which break down soybean proteins into amino acids and wheat starches into glucose.
Because failure to use enzymes with high decomposition performance will have a negative impact on all subsequent production processes, many brewers consider high-quality koji to be the most important factor of their operations. Therefore, soy sauce brewers throughout Japan purchase their mold from specialized koji fermentation starter producers.
Amino Acid Liquid and Alcohol
In addition to the main ingredients such as soybeans and wheat, some producers add additional ingredients including rice, umami seasoning such as amino acids, sweeteners (stevia, licorice root, saccharin, etc.), and preservatives (alcohol, sodium benzoate, etc.). In Kyushu and other regions where sweet-tasting soy sauce is preferred, amino acid liquids are frequently used as ingredients. The liquids are packed with umami constituents derived from corn, soybeans and other such base ingredients, and these liquids are mixed in with the finished (pressed) soy sauce and/or mixed in with the fermenting mash prior to fermenting and maturation.
Standard Soy Sauce Production Process
1.The soybeans are steamed.
2.The wheat is roasted and crushed, then mixed in with the soybeans.
3.The koji mold fermentation starter is mixed in.
4.The koji is allowed to proliferate in a special room.
5.The moromi (fermenting mash) is created by adding saline water to the koji.
6.The mixture is moved to vats where it ferments and matures.
7.Press equipment is used to extract the soy sauce product.
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
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.
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.
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.