The first things that come to mind when people think of soy sauce are usually that it is black, salty and comes from China. But in fact it is a lot more than that! It's one of those condiments that we take for granted and that no one ever gives any real thought to. But what is this black substance anyway?

First of all, the chances of you actually having Chinese soy sauce in your fridge are rather slim. Instead, the bottle you have stashed in the back of your refrigerator is more likely to be Japanese. And if the bottle, in addition, carries a label reading Kikkoman, there is no need to collect further evidence. Nonetheless, soy sauce does have its origins in China, dating back about 2,500 years. It has been thought to have served as a substitute for salt in times when this valuable commodity was too expensive for most people to afford. Since then, soy sauce has become the staple of kitchen cupboards all over the world.

First things first. The soybean.

The main ingredient of soy sauce, no surprises here, is soy. The pods of this small, hairy-looking legume belonging to the pea family usually contains two to three edible seeds. These beans contain a very complex protein compound and are rich in calcium, magnesium and vitamin B. Of all the beans in the world, soybeans contain the least amount of starch. All these beneficial nutritional qualities have contributed to soy's popularity all over the globe.

The art of fermentation

The process of making soy sauce starts with the soybeans being blended in with wheat to form a mixture that is then brought to a boil and mashed. It is then allowed to cool down, after which a fermentation agent called Aspergillus mold is added and the entire mixture is placed in perforated vats for fermentation. This mixture is called koji. After three days the koji is transferred to larger fermentation tanks. Water, salt, lactic acid bacteria and yeast are added to further stimulate the process. This substance, called moromi, is allowed to ferment in the tanks for many months - preferably outside under the radiant Chinese sun. During this time, the moromi turns into a reddish brown puree and develops more than 200 different flavor compounds.

Six months later it's time to separate the liquid from the solids. This is simply done by pressing the mass through layers of fine filtering cloth. It is then pasteurized and bottled to create the soy sauce we know and love.

Know your soy

Good soy sauce is like good olive oil. Just like there's extra virgin olive oil, there's extra virgin soy sauce, although it does not carry the same name. It's the soy sauce obtained from the first pressing. It has a light color, superior quality and carries the name tóuchōu (premium light soy sauce). Due to its delicate nature, this sauce is primarily used for dipping and not for food preparation. For the latter, there is lǎochōu, a darker sauce that has been allowed to ferment for a longer time. Its flavor deepens during heating, which makes it ideal for cooking.

Acid and salt

Soy sauce fermentation tanks. (Image: Wikipedia) The technique described in this article is the traditional way of making soy sauce. However, nowadays, many manufacturers opt for an alternative production process which is based on the use of hydrolysis. In short; the soy is boiled in hydrochloric acid, neutralized with sodium carbonate and mixed with syrup to create a darker color. It cuts the preparation time down to just a couple of days. Needless to say, these sauces are in no way comparable to the real thing.

Over the centuries, soy sauce has become a staple of many kitchens. Here in the West, we use it mostly in oriental dishes or as a salt substitute. So, the next time you open the fridge to grab a bottle of this traditional seasoning, take a moment to appreciate the amount of time and effort that has gone into creating this unique black delicacy.

Author: Maarten van Rijn

Edited by: Stina Björkell