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The Science of Soy Sauce

The Science of Soy Sauce

What is soy sauce and how is it made? From the ingredients to the preparation, here's a closer look at one of the world's most famous and tasty sauces.

By FDL on

Some flavours are so remarkable that they are sufficient to define an entire cuisine. For instance, what comes to mind if you think of sushi? Rice and fish, of course, but an unmistakable and ubiquitous note is provided by delicious soy sauce. Savoury yet aromatic. Down to earth but endowed with a mysterious colour. But do you really what is soy sauce and the way it is made?

The origin of soy sauce

The earliest evidence of soy sauce dates back to Ancient China, around 3000 B.C. It was called jiang and consisted in a liquid that formed when foodstuffs were preserved in salt. It was not until the Tenshō period in Japan, towards 1580 A.D. that a sauce more similar to the one we know today, a cross between soy sauce and miso paste, started to be sold in great quantities. Just think, an order for 18000 litres of soy sauce was registered in an ancient ledger dated 1588, to be shipped from Kishu to Osaka. But it was only in the Edo period, around 1688, that soy sauce started to be exported to other parts of the world, mainly thanks to Dutch merchant ships. To date, there are no precise figures regarding this particular market but, suffice it to say that the sales turnover of Kikkoman, the market leader, exceeded 3.3 billion dollars in 2014.

Soy sauce ingredients, the secret of taste

But what is the secret of soy sauce? Let's start from its ingredients. It obviously contains soya in the form of the well-known "soybeans". The most common type is generally used, yellow soybeans. In some cases, wheat flour is added to non-fermented or slightly fermented sauces, in an equal quantity to soya. This is spurned by tradition and by purists so be warned! Then, it will come as no surprise to learn that soy sauce contains salt. It takes a great deal of salt: 12 - 18% of the final weight of the sauce. In this century-old sauce, salt performs many functions. Its main purpose is to create a suitable environment for fermentation but it is also important as a preservative. Last but not least, it contributes to the unique flavour of the sauce itself. With these two or three ingredients, we can start to make soy sauce.

How is soy sauce made?

The first step is fermentation, which is necessary to obtain Koji. The best soybeans are carefully selected and then blended, before adding water. This mixture is then boiled until it becomes a soft puree. At this point, it is removed from the heat and cooled to 27 °C when a fungus is added to it. Don't be alarmed, we are talking about an edible fungus, the well-known Aspergillus, which causes fermentation to start. This process lasts for three days and takes place in a perforated vessel. The result of the process is a precious substance called Koji.

The Koji is then usually transferred to small barrels together with water and salt to form what is known as moromi, to which yeasts and lactic acid bacteria are added. Now, fermentation will continue for several months, during which time the liquid will become dense and reddish-brown in colour. After about six months, the unrefined soy sauce is strained through natural clean cloths, then the filtered liquid is pasteurized to improve its shelf-life and to increase the number of aromatic blends (of which there are over 200!). Once the liquid has cooled, the soy sauce is ready for bottling.

The method described above is the traditional one and, quite frankly, the one that food connoisseurs find most gratifying. No special equipment is required but it is necessary to follow a few important guidelines. First of all, carefully select the soybeans which must be fully ripe and healthy. Secondly, use dechlorinated water (leave it in a basin overnight) and, if possible, store the moromi in small wood barrels. Soy sauce made in this way keeps very well in the fridge for several months. All you have to do now, is to prepare some excellent sushi to do full justice to your sauce.

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