How Is Soy Sauce Made?
Soy sauce is made from fermented soybeans. The fermentation process creates alcohol and other chemicals which are then used to make the soy sauce. There are many different types of soy sauces available today including: regular, low sodium, light, dark, sweetened with sugar or honey and flavored with fruit juices and spices. Most varieties contain salt and sometimes other ingredients such as wheat gluten or corn starch. Some soy sauces may have added preservatives.
The main difference between the various kinds of soy sauce is the type of fermentation process used to create them. Regular soy sauce contains yeast that ferments sugar into ethanol, lactic acid and carbon dioxide (CO2).
These gases are released during fermentation resulting in a thickening effect on the product. Lactose is not fermented because it does not ferment well. Fermentation produces flavors and aromas that vary depending on the type of fermentation process used. For example, if the fermentation process uses sugar instead of yeast, there will be no flavor or aroma produced. If the fermentation process uses both yeast and sugar, there will be some flavor and aroma produced. However, when using yeast to produce soy sauce it is very difficult to get a good flavor without adding sugars or other additives.
There are several different kinds of fermentation processes commonly used to make yeast-based soy sauces:
1. Traditional – After soaking and cooking, the beans are mixed with a small amount of roasted grain (typically wheat) and mold cultures.
This mixture is left to ferment for a day or more, then it is transferred to another container where it is mixed with salt and the main yeast culture. The container is then sealed to prevent outside air from contaminating the mixture.
2. Intermediate – This is a modification of the traditional process.
A small amount of roasted grain (typically wheat or barley) is mixed with the soaked, cooked soybeans in a container. A small amount of mold cultures and yeast is added and this mixture is allowed to rest for several hours or even a day.
After this resting period, this mixture is combined with salt and the remainder of the mold and yeast cultures to ferment the soybeans. This mixture is then transferred to another container where it is mixed with more salt and sealed to prevent outside air from contaminating the mixture.
3. Quick – This method uses a chemical called xanthum gum or a genetically modified version of it to accelerate fermentation.
The bean mixture is mixed with a small amount of roasted grain (typically wheat or barley), xanthum gum and the main yeast culture. This mixture is left to ferment for a day or more, then it is transferred to another container where it is mixed with salt and sealed to prevent outside air from contaminating the mixture.
There are also some non-yeast types of soy sauce available that are made with other microbes such as mold or bacteria:
1. Mold – After soaking and cooking, the beans are mixed with a small amount of roasted grain (typically wheat) and allowed to ferment.
The mixture is then mixed with more roasted grain (typically wheat or barley) and a mold culture. This mixture is left to ferment for a day or more, then it is transferred to another container where more roasted grain (typically wheat or barley) and salt are added and the mixture is allowed to ferment.
Some of the fermented mixture is transferred to another container for fermentation.
2. Bacteria – After soaking and cooking, the beans are mixed with a small amount of roasted grain (typically wheat).
A small amount of the bacteria “Bacillus subtilis” is added and this mixture is allowed to rest for several hours or even a day. After this resting period, this mixture is combined with salt and the remainder of the bacteria culture and fermented.
With both the mold-based and the bacteria-based fermentation processes, after the beans are prepared they are mixed with just enough roasted grain (typically wheat or barley) to cover them and a small amount of a mold or bacteria culture. The mixture is then kept warm and tightly sealed for several days to allow fermentation.
Salt is added after the resting period and then the mixture is transferred to another container and more roasted grain (typically wheat or barley) and salt are added and it is allowed to ferment again.
In some parts of Japan, a special short-cut version of the traditional fermentation process was developed in recent years to speed up production. In this method, the soaked and boiled soybeans are mixed with a small amount of roasted wheat, salt and mold culture.
This mixture is left to ferment for several hours or even a day before being transferred to another container where more roasted wheat and salt are added.
Although this simplified process does produce a soy sauce with less complex flavor and aroma than the traditional method, it has become more popular in recent years since it is much faster.
Traditionally “koji” is used to start the fermentation process rather than yeast. This provides for a more complex flavor due to the variety of “koji” molds available.
These days, brewers usually just use the yeast “Saccharomyces cerevisiae” which gives a simpler flavor. A mixture of yeasts is usually used since only this single type of yeast does not provide for a good flavor or aroma profile.
Most Japanese soy sauce contains wheat as a source of food for the yeast, mold or bacteria. Some brewers, who use the traditional fermentation method without yeasting, still produce flavored soy sauces by mixing in other ingredients after the fermentation process.
Other ingredients such as fruit juice, various herbs and spices and even coffee beans are sometimes used to flavor soy sauce. These special flavorings are either added to the beans before fermentation or after.
A by-product of the production process is a solid left over called “koji”. This is a paste like substance and is typically around 5 to 25% of the weight of the original beans.
This is used as an ingredient in many Japanese dishes, especially in soups, stews and pickles.
The flavor of Japanese soy sauce varies greatly between varieties and even within brands. Typical flavor differences can be categorized by acidity and viscosity.
Acidity is less in light (or thin) varieties which also tend to have a lighter color and more salt. Thick (or dark) varieties tend to have more acidity, a darker color and less salt.
Some specialty soy sauces are very thick and cloudy with strong specific flavors. These flavored types are sweeter than the more commonly used light or thin soy sauce.
There are also some flavored soy sauces such as ponzu, usukuchi and kiwami which have different flavor profiles and ingredients.
Vinegar made from distilled alcohol is also called “su”. While it is not a genuine soy sauce since it does not contain any soy, wheat or salt, the terms “su” and “shoyu” are often used interchangeably by the public even though technically they are different products.
The words “shoyu” and “soy sauce” are sometimes used in Western countries as generic words for all types of soy sauce, including the sweetened varieties which are popular in Asian cuisines. These sweeter sauces tend to be flavored with things like fruit or sweeteners and are mostly used for dipping foods or in cooking.
In the US, most of the “soy sauce” served in restaurants is actually a salty condiment comparable to western style barbecue and steak sauces. It is typically used on Chinese food (often in the form of stir fry), egg rolls, French fries, breakfast sandwiches and other such foods.
In general, these “thick restaurant soy sauces” are not intended to be consumed as they are used for cooking rather than as a table condiment. They also tend to be less salty than the traditional thin “table soy sauces” which are used to flavor foods before cooking or as a dipping sauce.
In recent years, manufacturers have started producing a new type of “thick” soy sauce calledwhich has an even thicker consistency than regular usu and is used mainly as a dipping sauce.
Soy sauce has a long shelf life and will stay good for around 2 years if unopened. It should be kept in a cool, dry and dark place to maximize its shelf life.
Opened soy sauce will stay good for up to 1 year when stored under the same conditions. For extended storage, it can be kept in the refrigerator where it will keep for up to 2 years. It should always be kept away from foods with strong scents (such as onions) as it can easily pick up other flavors.
Soy sauce can be frozen although this is not recommended as soy sauce tends to pick up the flavor of other foods when defrosted.
There are also many different types of soy sauce available in most grocery stores. These include low-sodium, lite, less sodium and all unsalted varieties.
Although these may be a good substitute for people on restricted diets, they tend to be much blander than standard soy sauce.
Soaking the dried shiitake mushrooms in warm water before adding them to the mixture will help to reconstitute them and boost their flavor although this is not essential.
Sources & references used in this article:
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Soy products as healthy and functional foods by H Jooyandeh – Middle-East Journal of Scientific Research, 2011 – kingsvegetarianfood.ca
Promotive effect of Shoyu polysaccharides from soy sauce on iron absorption in animals and humans by M Kobayashi, Y Nagatani… – International …, 2006 – spandidos-publications.com
Cautions in the use of biomarkers of oxidative damage; the vascular and antioxidant effects of dark soy sauce in humans by CYJ Lee, HB Isaac, H Wang, SH Huang… – Biochemical and …, 2006 – Elsevier
Tempe, a nutritious and healthy food from Indonesia by M Astuti, A Meliala, FS Dalais… – Asia Pacific Journal of …, 2000 – Wiley Online Library