Shōyu (醤油, soy sauce) is one of the oldest umami elixirs in the world. For over a thousand years, it has been used to refine cuisine in Japan and, in similar forms, throughout East Asia. Yet, like many things, this long tradition has been fundamentally altered by industrialization. A cultural asset born of patience, an intuition for natural processes, and a connection to the seasons has been transformed into a fully mechanized industrial process—one that leaves little room for the natural development of life and flavor.

The following look behind the scenes shows what sets industrial manufacturing apart from traditional craft, as practiced at mimi ferments. They are two worlds that could hardly be more opposed: from the bean, through production, to those details that appear on no label and yet determine the taste.

At the end of this text, we reveal what this difference concretely means for you, and why mimi shōyu leaves even categories like the Ultra-Exquisite Selection behind. If you're in a hurry, you can jump straight there. If you come along the whole way, you'll understand why.

If you would first like to know how shōyu is actually made, you can read our article Shōyu: Origin, Production and Varieties.

Part 1 – The selection of raw materials: Marudaizu or Dasshi-kakō-daizu

"Soy sauce" promises that soybeans are its foundation. But the first fundamental difference between craft and industry begins with the raw material itself. Artisanal producers like mimi ferments use the whole, intact soybean—in Japanese, Marudaizu (丸大豆, whole soybean). It contains all native fats, proteins, and plant lecithins in their original, pristine form.

Modern soy sauce production, by contrast, uses a by-product: Dasshi-kakō-daizu (脱脂加工大豆, soybean meal), the defatted residue of soybeans left over from soy oil production, unless "Marudaizu" is explicitly stated on the packaging. Although the complete utilization of raw materials and the upcycling of byproducts make economic and ecological sense, the oil extraction process itself is highly critical. The reason for this lies in the high degree of processing and the use of the solvent n-hexane:

Excursus: How is defatted soybean meal made? To extract soybean oil, the beans are mechanically broken open. The husks are blown away, and the remaining kernels are heated and rolled into thin flakes to increase their surface area. Because soybeans contain relatively little oil, purely mechanical pressing is not enough, however. Therefore, the flakes are placed in an extractor to wash out all the oil using n-hexane, a solvent derived from petroleum. The defatted flakes, now soaked with hexane, then pass through a so-called desolventizer-toaster, in which the hexane is evaporated with steam at well over 100 °C. What remains is a heavily processed, dry protein skeleton: soybean meal. n-Hexan is toxicologically a confirmed neurotoxin [1]. Furthermore, in practice, no chemically pure hexane is used, but rather "technical hexane"—a mixture of various hydrocarbons that can vary depending on the batch and source [1]. The idea that hexane is "residue-free" in the final product is merely an assumption: laboratory analyses sometimes detect minimal traces of hexane in refined oils and defatted protein fractions [2], and the EU permits legal maximum levels of up to 30 mg/kg for defatted soy products—so residue-free status is not even legally mandatory [3]. The European Food Safety Authority (EFSA) also sees a need for clarification: in 2024, it classified the previous 1996 safety assessment of technical hexane as no longer sufficient and called for a comprehensive reassessment [4]. Regardless of this, refined foods are generally considered critical in holistic nutrition. Dr. Max Otto Bruker saw this as a prime example of how food is broken down by heavy processing into isolated, denatured fragments that, according to his clinical findings, cause chronic diseases. (Read more in his standard work "Unsere Nahrung – unser Schicksal" / "Our Food – Our Fate"). That this assessment is highly topical is underpinned by modern biochemical studies. [5].

Why does the industry turn to soybean meal? It is cheaper, protein-rich, and contains almost no fat that could turn rancid. When pressing the Moromi (諸味, Maische) from whole beans, an oil layer forms that must be removed—with defatted meal, this step is eliminated.

The catch: The flavor falls by the wayside. Whole soybeans bring valuable plant fats and lecithins. During a months-long, slow fermentation—as is the case at mimi ferments—these building blocks transform into complex ester compounds and delicate aromas. The lecithin contained is organically broken down into glycerin and choline. These act as natural emulsifiers, bind the aromas perfectly, and give the sauce its characteristic, harmonious softness on the finish. A "meal-based sauce," by contrast, often tastes one-dimensional in comparison: salty, flat, bitter, metallic, or astringent.

The reason lies in chemistry: For Umami (旨味, savory taste), free amino acids are primarily required—above all glutamic acid, which is cleaved from the proteins by koji enzymes. However, the proteins in soybean meal are only partially available for fermentation. Due to the extreme oil extraction processes, they are thermally damaged and denatured. The highly specialized enzymes, however, can only cut the amino acid chains at very specific sites—sites that are blocked by uncontrolled, premature Maillard reactions during oil extraction. In this process, proteins "fuse" with the remaining sugars of the bean and form strong chemical bonds that the koji enzymes find difficult to break down. Instead of umami, bitterness is produced. Studies also show that on heavily denatured meal, the koji enzymes form different peptide chains than on the intact bean: significantly more hydrophobic peptides and amino acids like isoleucine, which are perceived as bitter [6,7].

Whole beans, on the other hand, promote the formation of Amadori compounds and γ-glutamyl peptides during long-term aging [8,9,10,11,12], which are responsible for the deep, meaty-creamy Kokumi-feeling(コク味, mouthfulness) —that special richness of flavor that defines a good shōyu. This biochemical structure also fundamentally changes the physical behavior of the sauce: while soybean meal-based sauces are watery and run right off food, a traditional Marudaizu shōyu has a higher viscosity thanks to the emulsifiers of the natural soybean oil. It coats the surface of meat, fish, or vegetables perfectly and clings to the palate as a silky film. This harmony of lipids and kokumi peptides is especially evident on warm rice or fatty sashimi: the sauce doesn't just run off but combines with the fats and starch of the food into a unified taste. As a result, the flavor doesn't drop off immediately but envelops the senses in a long-lasting, harmonious finish.

Even the storage of raw materials plays a role: bone-dry, fat-free protein meal sounds like it has long shelf-life potential. However, the significantly increased surface area of the meal required for oil extraction promotes protein oxidation during prolonged storage. Atmospheric oxygen attacks the amino acids; the protein chains fold over and form disulfide bridges with each other—true chemical cross-linking. The proteins clump, and the yield of free nitrogen and glutamic acid drops dramatically. In plain language: the sauce loses massive potential for natural umami—a loss that the industry subsequently attempts to mask with additives.

 

Three ingredients or whatever else gets added

Traditional shōyu consists of exactly three ingredients: soybeans, wheat and salt. Through fermentation, flavor arises naturally, above all glutamic acid, the natural umami. Industrial sauces skip this maturation process or use soybean meal, and compensate for the missing flavor artificially instead:

Flavor enhancers

• Mononatriumglutamat (E621) – the best-known additive for a quick, intense umami taste
• Dinatriumguanylat (E627) and disodium inosinate (E631 / E635) – extremely potent enhancers, often combined with glutamate to multiply its effect
• Yeast extract – legally not an "additive" but declared as an ingredient; however, in practice, it serves the same purpose: a glutamate substitute for a "clean label"

Coloring agents for appearance

Because shortened production times are not enough to develop the typical deep-brown to black color naturally, they assist—using caramel color (E150a–E150d), roasted or chemically treated sugar, especially common in "dark soy sauce".

Preservatives

Traditional soy sauce preserves itself through its very high salt content and lactic acid bacteria. Cheap mass-market products often lower the salt content or want to guarantee a particularly long shelf life through:

• Sodium benzoate (E211): Prevents the growth of yeasts and molds in cheaply produced sauces.
• Potassium sorbate (E202): Another very common preservative in mass-market Asian imports.
• Alcohol: For certain Japanese lines, a minimal amount of pure alcohol is added to the sauce. It serves as evaporation protection for lipophilic aromas and prevents wild yeasts from forming on the opened sauce when stored at room temperature.

Sweeteners and acidity regulators

• Sugar, fructose-glucose syrup, sweeteners: Used to mask the extremely salty or sometimes bitter taste of chemically produced sauces.
• Lactic acid, acetic acid, or citric acid (E330): Artificially added to imitate the sour taste of natural fermentation.

The extent to which a product is allowed to rely on these auxiliaries is regulated by law in Japan—via the brewing methods Honjōzō (本醸造, authentic brewing), Kongōjōzō (混合醸造, mixed brewing) and Kongō (混合, blended). We explain exactly what these terms mean and how you can recognize them on a label in the Shōyu Lexicon at the end of this article.

The good news: The traditional Honjōzō brewing method dominates the Japanese market. According to the MAFF (Japanese Ministry of Agriculture, Forestry and Fisheries), about 90 percent of soy sauce produced in Japan is made using this method [13]. n this process, no amino acid solutions or enzymatically or fermentatively broken-down seasoning liquids are added. Instead, the sauce is created through the fermentation and aging of koji, soybeans, wheat, and salt. Furthermore, the Kongōjōzō and Kongō products with artificial amino acid solution are, moreover, mostly not available in supermarkets at all, but are used directly in convenience meals or commercial kitchens.

But take note: Honjōzō does not automatically mean "free of additives." The production method says nothing about whether flavor enhancers or sweeteners have been added to the finished product. Such additives are generally permissible in Honjōzō sauces as well, though it is rather rare. However, it is common practice to use both flavor enhancers and sweeteners in shōyu seasoning sauces like ponzu, dashi-shōyu, sashimi shōyu, or sweet soy sauces from Kyushu. The actual share of additive-free soy sauces in the overall Japanese market cannot be precisely determined, as neither the MAFF nor the Consumer Affairs Agency publishes such figures. If you want a shōyu without additives, you should look for the label Mutenka (無添加, without additives). But the devil is in the details here, which you can also read about in the Shōyu Lexicon below.

Part 2 – Production via the senses or the sensor

In a traditional manufactory, koji grows in Koji-Buta (麹蓋), shallow wooden boxes made of Sugi (杉, Japanese cedar). During the two- to three-day maturation period, the soy-wheat mixture is regularly turned by hand so that it grows and breathes optimally. Depending on the stage, the boxes are stacked differently: directly on top of each other to retain heat, slightly offset for more air circulation, in a brick pattern, or layered at an angle. When to turn and how the boxes are laid is decided by the experience of the Tōji (杜氏, master brewer) or the Muromae (室前, koji master) – not by a rigid schedule.

Observation occurs through all senses. Even before entering the Koji-Muro (麹室, fermentation room for koji), one can notice the typical koji scent and assess exactly how far the koji has developed and how it is faring based on the smell alone. Once in the muro, one can perceive the room's heat and humidity throughout one's entire body. If one passes your hand over the koji—without touching it—one can sense the intensity and exact distribution of this heat. When one finally touches the koji, one can feel its texture. Tasting a few grains provides insight into the level of sweetness and, thus, the degree of maturity. While turning the koji, one can even experience how moist it is visually and audibly: wetter grains make a duller sound than dry ones, and moist grains stick together more, so they tend to tumble rather than trickle. In this way, direct and comprehensive sensory impressions flow together and, with experience and intuition, form a deep bond between people, natural process and product.

Fully automatic, aromatically off

In industrial production, humans hardly see anything of the raw materials. The raw materials are transported from silos through conveyor pipes directly into large machines and processed automatically. The koji matures in fully automatic large-scale facilities—so-called rotary koji makers—and is turned, ventilated, and cooled under computer control. The finished koji is then directed through closed pipe systems into tanks to continue maturing as a mash. The Moromi not aged at room temperature, but year-round at elevated temperatures of around 35 to 40 °C. Enzymes work significantly faster at higher temperatures—according to studies, this can shorten the fermentation time from the traditional six to twelve months to just three to four months.

In this fully automatic manner of production, the role of the human is reduced to pressing buttons instead of participating directly in the fermentation process. The immediate whole-body perception, the synthesis with one's own experience, the realization of an individual signature gives way to reading transmitted information, a pre-programmed sequence and the reactive operation of equipment. Cleaning and maintaining the machines now take more time than interacting with the living production process. That such soy sauces taste metallic, flat and characterless is the direct consequence of this path.

What is lost here is not a peripheral detail but strikes a core point: the simple material equation does not add up. Pure material supply is not enough for living things to thrive. In the well-known experiments by psychologist Harry Harlow, young rhesus monkeys that were provided with food by a wire dummy but deprived of any affection developed severe behavioral disorders—some did not survive the isolation. On a smaller scale, this also applies to fermentation: even with sourdough bread, the slightest temperature fluctuations in the bakery or weather conditions noticeably change the leavening power and taste—a standardized program misses this dynamic. While much of this can be captured in numbers, such as sugar or acid content, such values remain mute on their own as long as no one relates them to one another. This is exactly what only a human can do, and even then not from the start: only over years does that intuition develop which enables a Tōji or Muromae to condense their sensory perceptions into an intuitive overall picture, from which one can read when to stir, cool, or leave it in peace. It is precisely this daily listening and intuitive acting that creates a connection to the process that no sensor can replace—and this is exactly what makes a product taste alive in the end.

Even faster, even cheaper

Even more can be saved in the production process. Instead of laboriously growing koji on soybeans and wheat over days, biotechnologically produced enzymes can be added directly to the mash, considerably faster and cheaper. These enzymes are produced in large bioreactors from waste products by microorganisms that have practically without exception been genetically modified.

The great paradox of the EU: This is where it becomes particularly interesting for you as a consumer, as the EU has created one of the most curious legal situations in food law regarding this:

1. The fungi and bacteria in the bioreactor are legally classified as clearly genetically modified organisms and are subject to the strictest safety controls.
2. As soon as they secrete their enzymes into the nutrient broth, the living cells are completely filtered out. The isolated enzyme powder contains no DNA and no living microbial cells – and therefore does not count as a GMO.
3. Because the finished enzyme no longer contains modified DNA and is destroyed during the final heating process, it is legally considered a technical processing aid. It does not have to be declared as "genetic engineering" in the EU.

If you want to reliably avoid genetic engineering, look for the EU organic seal: in controlled organic production, the use of enzymes from genetically modified microorganisms is strictly prohibited by law. An organic shōyu or organic miso, as at mimi ferments, may never use such laboratory catalysts.

Even more drastic: Acid hydrolysis: In this process, the soy-wheat mixture is completely broken down into its amino acid building blocks within a few hours using hydrochloric acid under pressure at 100 to 130 °C. The resulting liquid is extremely acidic and inedible and must be neutralized with caustic soda. This purely chemical process has nothing to do with biological fermentation anymore – instead of the countless parallel reactions of a natural maturation, only a single process takes place here, and the taste remains correspondingly one-dimensional.

These so-called amino sauces (Hydrolyzed Vegetable Protein, HVP for short) are also widespread in Europe – and involve another trick: when neutralizing the hydrochloric acid with caustic soda, water and around 16 to 20 percent salt are produced. Since this salt is not added as an ingredient, but is formed chemically, it does not have to be declared. Seasoning sauces made from hydrolyzed vegetable protein appear "salt-free" according to the list of ingredients – even though they contain significant amounts of salt.

All this has little to do with true shōyu tradition – and fortunately, there is no soy sauce in Japan that is produced exclusively in these ways. The Japanese Agricultural Standards (JAS) even prohibit the sale of pure amino acid solution as soy sauce. Nevertheless, around 10 percent of soy sauces sold in Japan are mixed with amino acid solution [14]; so-called mixed soy sauces may consist of up to 80 percent amino acid solution. Interestingly, the protein source is arbitrary: any vegetable protein source may be used for this.

Part 3 – The invisible ingredient: What appears nowhere on the label – and yet determines everything

Traditional shōyu – as with mimi ferments – matures for years in wooden barrels, the Kioke (木桶, wooden barrel). Wood breathes, reacts to the seasons, and over decades, an extremely diverse community of salt-tolerant yeasts and bacteria settles in the millions of tiny pores. Centuries-old barrels often hardly look like wood anymore: their surface breaks open like puff pastry and is spotted differently depending on the microorganism. Especially with shōyu, the flora of the entire building plays a decisive role, because the barrels stand open in traditional manufactories – the mash is exposed to the air for years. Microorganisms from roof beams and gables trickle continuously into the mash and at the same time originate from it. The mash in traditional manufactories is thus a very open system that is in constant exchange with the environment of the manufactory. In Japan, there is even a special term for this in-house microorganism cosmos: Kura-tsuki (蔵付き). Wild yeasts give the shōyu its fruity, floral aroma; in-house lactic acid bacteria produce a wide spectrum of organic acids. Even natto bacteria (B. subtilis), which are strictly avoided during koji fermentation, play an important role in the mash: per cell, it contributes the most umami, as it has an extremely potent, salt-tolerant enzyme called gamma-glutamyltransferase, which releases an enormous amount of amino acids.

Becoming and passing – the seasons of a wooden barrel

The fermentation of the mash proceeds in waves, shaped by the season and the age of the barrel. In the cold winter, when traditional mashing (諸味仕込み, Moromi-jikomi), takes place, there is hardly any microbial fermentation – instead, the enzymes of the koji silently break down soybeans and wheat into amino acids and oligosaccharides. In the spring, the barrel awakens: lactic acid bacteria spread rapidly and lower the pH value of the mash to about 5. In the summer, the yeast reaches its peak, the mash begins to bubble actively, and complex, fruity ester compounds are formed. B. subtilis is also particularly active in the summer: via its enzyme gamma-glutamyltransferase, it releases additional glutamic acid, and from amino acid precursors such as L-threonine, it forms alkylpyrazines [15,16,17] – those flavorings that also give the closely related Bacillus ferment natto its nutty-roasted, partly chocolatey notes and here combine perfectly here with the fruity yeast esters. In autumn, peace returns, many microorganisms die, and the taste undergoes its final harmonization.

Dying also contributes to the taste. Each cell contains a multitude of substances that pass into the mash upon death – usually via controlled, programmed cell death (apoptosis). In its final hours, the cell produces enzymes for self-dissolution (autolysis) at the expense of energy. In this way, it not only releases amino acids, fatty acids, and sugars, but also breaks down its DNA and RNA into individual nucleotides [18,19,20,21,22]. This creates guanosine monophosphate (GMP) and other nucleotides, which multiply the umami impression of glutamic acid. At the same time, autolysis shifts the acid balance: organic acids such as citric, tartaric, succinic, and lactic acid increase initially and are broken down again in the further course of maturation – an ebb and flow that is directly reflected in the flavor profile of the finished sauce [23,24]. Some of the signature flavors of shōyu also originate from the same autolysis process: ethanol, the floral 2-phenylethanol, and the spicy-smoky 2-methoxy-4-vinylphenol [25,26,27]. What remains shapes the texture: the released peptides act like tiny Velcro fasteners and increase viscosity, glycerin and sugar alcohols coat the tongue like a fine film, and both together soften the sharp sting of salt into a gentle, even salt perception. The organic acids from the lactic acid fermentation also contribute to this balance by coming into equilibrium with the sodium chloride and thus rounding off the piercing peaks of the salt. Finally, the lipids of the whole soybean act as a natural emulsifier: they bind and fix the volatile aromatics so that they remain on the tongue for longer, and soften the salt impression – similar to glycerin and peptides.

In industrial mass production according to ISO standards, none of this exists: no natural flora, no open barrel, no seasonality. The production facilities have smooth epoxy floors, the mash is stored in gigantic, hermetically sealed tanks with an epoxy resin inner lining. Computers and algorithms take care of stirring, heating, and aeration. Instead of hundreds of different microorganisms, usually only two or three strains bred for efficiency are used [28,29,30]. Complex side reactions that are so important for the full-bodied taste do not take place here.

The price of convenience: tasting the tank

Why use epoxy tanks at all? For industrial production, wooden barrels are simply too expensive, too maintenance-intensive, hardly scalable, and difficult to sterilize. For a time in Japan, there were almost no craftsmen left who could even build or repair these cedar barrels. Shōyu matured in wooden barrels is an absolute niche product with a market share of about 1.5 percent. The only alternatives were stainless steel and enamel. Enamel is hardly used today – brittle, sensitive to impact, expensive. And the salty, acidic mash challenges even stainless steel in the long run; only very expensive special alloys can withstand it, which are simply unaffordable for most manufacturers – in a shrinking market. In practice, epoxy resin remains the standard: inexpensive, elastic, easy to repair.

However, under the acidic, salty conditions of months of fermentation and decades of use, even this plastic layer does not remain inert. Despite official certification, trace amounts of chemical compounds such as bisphenols can migrate directly into the food [31,32]. EU authorities are now countering this risk with a general tightening of limits for all food contact materials – a measure that affects the entire food industry and also presents the traditional methods of shōyu production with new regulatory challenges.

When epoxy resin ages, is exposed to heat or comes into contact with aggressive substances, various compounds can leach out of the polymer matrix: bisphenol A (BPA) and its derivatives, the basic building block of most epoxy resins; if the mixing ratio in the tank coating is not accurate to the microgram, unbound molecules remain that slowly leach out. Epichlorohydrin and BADGE, reactive intermediates of resin production whose residues can likewise migrate. And benzyl alcohol as well as reactive diluents from the hardeners, which make the resin pliable and often migrate more easily than the resin itself.

Soy sauce is almost the worst-case scenario for epoxy tanks because it combines almost all the migration-accelerating factors of food chemistry:

• The pH value: Due to the lactic acid fermentation, it is only 4.6 to 4.8. Acid microscopically attacks epoxy surfaces and leaches out migrants significantly faster than pure water.
• The contact time: An epoxy resin cup is harmless because the coffee is drunk after 15 minutes. Soy sauce mash, on the other hand, is stored in the same tanks for 6 to 24 months at a time – an extreme long-term exposure that massively increases the amount of migration.
• The salt content: In high concentrations, salt has a highly corrosive effect and permanently challenges the barrier properties of the coating.
  

What this means for mimi ferments: We mature exclusively in wooden barrels – without epoxy, without plastic lining, without compromise. And because whole organic beans, open kioke barrels, and years of maturation at room temperature release so much natural umami potential, our shōyus achieve protein levels that go far beyond the legal Japanese top class Tokkyu – up to the highest, voluntary luxury class Cho-Tokusen. More on this in the Shōyu Lexicon immediately following.

The Shōyu Lexicon

Quality classes and types: how to understand the Japanese label

Three groups of terms describe what is in the bottle: the brewing method, the post-treatment, and the brewing ingredients. In addition, there is a quality system that quantifies the umami content of a shōyu.

Brewing method

The 3 official Seizo-hōhō (製造方法, manufacturing methods) according to the Japanese Agricultural Standard (JAS standard):

An additional class and the wooden barrel:

Tennen-jōzō (天然醸造, natural brewing method) is not an independent fourth category in the main JAS system, but a legally protected additional designation for Honjōzō, in which no additives and no temperature control of the mash are allowed.

The term Kioke Shōyu (木桶醤油, wooden barrel-matured shōyu) is not a legal quality class in the JAS system, but describes exclusively the maturation vessel (wooden barrel) in food law. It has been included here because it strongly influences the brewing method and is an important quality feature and identifying mark for many manufactories. Legally speaking, the term does not regulate ingredients or additives. A kioke shōyu can therefore theoretically be a cheap kōngō soy sauce with amino acid solution and sweeteners. In practice, purist craft breweries almost always use the extremely expensive and maintenance-intensive wooden barrel in combination with the Tennen-jōzō class and whole soybeans (Marudaizu).

Post-treatment

Ki Jyōyu (生醤油) – pasteurized and filtered. It is the Japanese standard shōyu that keeps for several years at room temperature unopened and remains virtually indefinitely stable even when opened in a warm kitchen. The heat not only inactivates enzymes and microorganisms, but also deepens flavor and color through the Maillard reaction – a trick that gives even shorter-matured or inferior sauces more flavor.

Nama Shōyu (生醤油) – pasteurized and filtered. It is the Japanese standard shōyu that keeps for several years at room temperature unopened and remains virtually indefinitely stable even when opened in a warm kitchen. The heat not only inactivates enzymes and microorganisms, but also deepens flavor and color through the Maillard reaction – a trick that gives even shorter-matured or inferior sauces more flavor.

Kiage Shōyu (生揚げ醤油) – neither pasteurized nor filtered. Freshly pressed, absolutely untreated raw shōyu full of active enzymes, koji fungus residues, yeasts, and lactic acid bacteria – the most unadulterated, lively form a shōyu can take; even in Japan, it is not available in normal supermarkets. It tastes full-bodied and lively and, thanks to its active microbiology, is suitable not only for marinating but also for further fermentation. Thanks to its fully preserved enzymes and antioxidants, it is also particularly healthy. At mimi ferments, this is not a special case, but our standard: every one of our shōyus leaves the manufactory exclusively as Kiage – raw, unpasteurized, unfiltered, with its complete, living microbiology.

Brewing ingredients

• Marudaizu (丸大豆) – made from whole soybeans, without soy grits
• Daizu (大豆) – soybean, most likely soy grits
• Yūki (有機)– all ingredients come from controlled organic cultivation
• Aminosan-eki (アミノ酸液)– amino acid solution
• Chōmiryō (Aminosā-tō) (調味料/アミノ酸等)– flavor enhancers (amino acids, etc.). Legal collective term for artificial umami (mostly MSG mixed with nucleic acids)
• Mutenka (無添加)– Additive-free: A voluntary producer claim that has only been strictly regulated since 2024. But beware: what is considered an additive in Japan is not necessarily identical to current EU law. Furthermore, "Mutenka" does not necessarily mean the product is free from all forms of additives—it may only be free from a specific category of substances. For example, Chōmiryō-Mutenka (調味料無添加) merely means: free from MSG / artificial umami. Additionally, until the recent change in law, there was hardly any regulation regarding the hidden carry-over effect of additives. This means: if the raw materials already contained additives, the producer could still label their end product as "Mutenka" as long as they did not add anything themselves during the final processing step.

Quality Classes

In Japan, official shōyu varieties are divided into three legal classes. To express the quality of a shōyu in figures, the JAS has taken two different approaches. The total nitrogen content of a shōyu is a reliable indicator of protein content, umami intensity, and aging duration, as nitrogen is only found in proteins. To reliably evaluate low-protein shōyu as well, there is a second factor: the total content of dissolved solids without salt (Total Soluble Solids without Salt). This TSS value measures everything that has been liquefied in the barrel by enzymes—that is, the sum of dissolved sugars, amino acids, peptides, and organic acids. Dark shōyu can thus shine with high protein values, and light shōyu with high density.

JAS Quality Grades Measured by Total Nitrogen

Since the total nitrogen content is rarely stated on a bottle, we have converted the JAS values into protein content in g per 100 ml (nitrogen × 6.25, the internationally common conversion factor).

The last two classes, Tokusen and Chō-Tokusen, are not a legal requirement, but rather a voluntary award from the Japan Soy Sauce Association for manufactures that age their products far beyond the legal top class, Tokkyū.

JAS Quality Grades by Extract Content (TSS without Salt)

Sources:

1. ATSDR Toxicological Profile for n-Hexane

2. Headspace analysis für residual hexane in vegetable oil

3. Hexan in Lebensmitteln: Bedeutung, Risikobewertung und Analyseverfahren

4. Technical Report on the need for re-evaluation of the safety of hexane used as an extraction solvent in the production of foodstuffs and food ingredients

5. Soybean oil induces neuroinflammatory response through brain-gut axis under high-fat diet

6. Soybean (Glycine max) Protein Hydrolysates as Sources of Peptide Bitter-Tasting Indicators: An Analysis Based on Hybrid and Fragmentomic Approaches

7. Bitter Peptides in Fermented Soybean Foods - A Review

8. Differences in taste and material basis of soybean and defatted soybean fermented soy sauces and influence factors

9. Quantification of twenty Amadori products in soy sauce

10. Decoding bitter peptides in soy sauce

11. Determination and quantification of the kokumi peptide, γ-glutamyl-valyl-glycine, in commercial soy sauces

12. Comparative study on the novel umami-active peptides of the whole soybeans and the defatted soybeans fermented soy sauce

13. Marktanteil Honjozo*

14. Marktanteil an Sojasaucen mit Aminosäurelösung*

15. Characterization of Bacillus subtilis gamma-glutamyltransferase and its involvement in the degradation of capsule poly-gamma-glutamate

16. Pyrazines Biosynthesis by Bacillus Strains Isolated from Natto Fermented Soybean

17. An Alkylpyrazine Synthesis Mechanism Involving l-Threonine-3-Dehydrogenase Describes the Production of 2,5-Dimethylpyrazine and 2,3,5-Trimethylpyrazine by Bacillus subtilis

18. Autolysis of Aspergillus oryzae Mycelium and Effect on Volatile Flavor Compounds of Soy Sauce

19. Induction and Repression of Hydrolase Genes in Aspergillus oryzae

20. Microbiological Characteristics and Physiological Functionality of New Records of Yeasts from Wild Flowers in Yokjido, Korea

21. Insight into the formation mechanism of umami taste in traditional Chinese soybean paste: A review

22. Valorization of Food By-Products into a Zero-Waste Broth: Effects of Yeast Extract on Composition and Sensory Properties

23. Autolysis of Aspergillus oryzae Mycelium and Effect on Volatile Flavor Compounds of Soy Sauce

24. Physiological and transcriptomic analyses revealed the change of main flavor substance of Zygosaccharomyces rouxii under salt treatment

25. Autolysis of A. oryzae Mycelium

26. Defatted Soybean Meal-Based Koji Promotes Flavor Development in Deyang Baiwo Soy Sauce: A Comparative Multi-Omics Study

27. Insights into Physicochemical Characteristics, Flavor Development, and Microbial Succession During the Natural Fermentation of Sichuan-Style Black Soybean Soy Sauce

28. Selection of micro-organisms for use in the fermentation of soy sauce

29. Monitoring of the microbial communities involved in the soy sauce manufacturing process by PCR-denaturing gradient gel electrophoresis

30. Industrial production of soy sauce

31. Factors affecting migration kinetics from a generic epoxy-phenolic food can coating system

32. Long-term migration from epoxy and acrylic-phenolic coatings

33. Anteil Marudaizu in Sojasaucen*

34. Art of barrel-brewed soy sauce revived for future generations*

35. Umami Information Center*

36. Anteil Biologischer Anbau Japan*

37. Soy Sauce and Local Cuisine*

38. A matter of national security*

*Note on data sources: The indicative figures given for traditional production methods (such as Kioke wooden-barrel ageing and Tennen-jōzō) are based on consensus data from Japanese industry associations and the current state of specialist literature. Due to the highly niche nature of this craft, no comprehensive government data collection exists on this subject. However, the figures reflect the generally accepted and plausible consensus among experts.