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Sauces and condiments from Japan

Gen'en and usujio shoyu (reduced- and low-salt soy sauce)減塩しょうゆ

Gen'en (reduced-salt) shoyu has 9 g of salt or less per 100 g, about half that of normal koikuchi; low-salt shoyu, sold as usujio, asajio, amajio or teien, has 80 % or less of the normal salt. Kikkoman makes its gen'en shoyu by brewing an ordinary koikuchi and then taking part of the salt out, and a 1980 interview describes doing this with ion-exchange membranes.

Recipe

No fixed amounts recordedThe product is defined by its salt content, not by a recipe.
Brewed koikuchi soy sauceThe ordinary dark soy sauce is made first; part of its salt is then removed, keeping the umami and aroma[jssa-def][kikkoman-pr2017]
SoybeansKikkoman's 2017 gen'en shoyu uses 100 % whole soybeans; the usual koikuchi method steams soybeans or defatted soybeans[kikkoman-pr2017][soysauce-info]
Roasted wheatIn the usual koikuchi method, mixed with the steamed soybeans in about equal amounts[soysauce-info]
Salt water (brine)Mixed with the koji in a tank to make the mash (moromi) of the koikuchi, which is then pressed[soysauce-info]
Starterkoji/qu/mold-starter (as for normal shoyu)
Start
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What changes: An ordinary soy sauce is brewed and pressed at full salt

Step 1 of 4
Brew and press a normal soy sauce
Time
Not documented
Temperature
Not documented
Salt
17.5 %
Reported
Acidity
Not documented

Output: raw or pasteurised soy sauce at normal salt.

Flavour
Not documented
Texture
Not documented
Colour
Not documented

Microbes at work in this step

Not documented for this step.

Method

Measured measured in a studySet fixed by a specification or tested recipeReported one source reports itTypical a general value, not sourced for this fermentUnconfirmed not yet checked against a source

At a glance

Gen'en (reduced-salt) shoyu has 9 g of salt or less per 100 g, about half that of normal koikuchi; low-salt shoyu, sold as usujio, asajio, amajio or teien, has 80 % or less of the normal salt. Kikkoman makes its gen'en shoyu by brewing an ordinary koikuchi and then taking part of the salt out, and a 1980 interview describes doing this with ion-exchange membranes. Salt is 17.5 % (Japan Soy Sauce Brewers' Association 2006). In the koikuchi soy sauce that gen'en shoyu is made from (Japanese soy sauce brewing in general) - koji mould Aspergillus oryzae or A. sojae and In the same koikuchi - Tetragenococcus halophilus do most of the fermenting.

Key numbers
Salt17.5 %Reported[jssa2007][kikkoman-pr2017]Brew and press a normal soy sauce

What makes this one different

Gen'en shoyu is cut to 9 g of salt or less per 100 g, and low-salt shoyu to 80 % or less of the normal salt of its type. Kikkoman makes its gen'en shoyu by brewing a normal koikuchi first and then removing the salt.

Related ferments

Safety

Normal soy sauce relies on high salt, and a laboratory paper notes that the high salinity of soy sauce fermentation helps prevent microbial growth (Wang 2021). Gen'en shoyu carries about half that salt.

History and sources

Every number is labelled with how it is known. How this atlas is made

The soy sauce industry's labelling agreement on "usujio", "asajio", "amajio" and "teien" was made in 2006 and revised on 19 March 2007. It lists the normal salt of each type (koikuchi 17.5 %, usukuchi 19.1 %, tamari 17.9 %, saishikomi 15.6 %, shiro 17.9 %) and says these values had been given to the Ministry of Health for the nutrition labelling standard that took effect on 24 May 1996. A 1980 Kikkoman interview records desalting soy sauce with ion-exchange membranes. In 2017 Kikkoman launched a whole-soybean gen'en shoyu made by removing salt from koikuchi.

  1. [jssa-def] Japan Soy Sauce Association, definition of reduced-salt and low-salt soy sauce, quoted in Nihon Shokuryo Shimbun, 減塩の日 keyword page (from Shokuhin Sangyō Jiten, 9th ed.)web
  2. [kikkoman-pr2017] Kikkoman 2017, press release on the whole-soybean reduced-salt soy sauce (特選 丸大豆減塩しょうゆ), Kyodo News PR Wireweb
  3. [jssa2007] Japan Soy Sauce Brewers' Association, Japan Soy Sauce Industry Federation and Japan Soy Sauce Technology Center 2006 (revised 19 March 2007), しょうゆの表示等に関する業界申し合わせ (industry agreement on soy sauce labelling), item on "usujio", "asajio", "amajio" and "teien" labelsspec
  4. [ito2021] Ito K., Matsuyama A. 2021, Koji Molds for Japanese Soy Sauce Brewing - Characteristics and Key Enzymes, Journal of Fungi 7(8):658 (soy sauce brewing in general, not gen'en shoyu)paper
  5. [soysauce-info] Soy Sauce Information Center (Japan), 製法 (how soy sauce is made), koikuchi honjozo method and label termsweb
  6. [soyinfo-hawaii] Shurtleff W., Aoyagi A. 2021, History of Soybeans and Soyfoods in Hawaii (1847–2021), Soyinfo Center (1980 Kikkoman interview on desalting by ion-exchange membrane)book