Everything you need to know about… soy sauce

What’s two and a half thousand years old, handy in a Chinese kitchen and capable of making almost anything delicious? No, it’s not your Chinese grandma. It’s that most Asian of seasonings: soy sauce.

This liquor of the gods is the continent’s staple ingredient, used everywhere from China, Japan and Korea to Vietnam, Thailand, Singapore and even over the ocean in Hawaii. Oh and in almost every Hong Kong kitchen too, from the remaining dai pai dongs and sui mai shops to Michelin-star eateries and virtually every household.

It’s even crept into western cuisine, used to ramp up salt and umami flavours in stews, casseroles, barbecue sauces, all kinds of marinades and just about anything else savoury. El Bulli’s soy sauce clouds come to mind as the ultimate example.

The point of this post is to give you everything you might want to know about the dark and mysterious liquid in one place. We’ve sifted through the bilge and taken out the boring bits to leave a final product distilled into less than a thousand words, which we hope will be almost as satisfying as the sauce itself.

What is it?

Soy sauce is a liquid seasoning made from a paste of soybeans and wheat, mixed with salt and water, and fermented with moulds with fancy scientific names. These are good moulds: magic, living flavour factories.


Given that it was first made around 2500 years ago, the finer details of the sauce’s origins are not crystal clear and vary depending on the source. It’s generally agreed though, that soy sauce originated from an attempt to preserve ingredients.

Various fermented pastes called jiang, made by preserving meat, fish, vegetables and grains with salt, were used in China as far back as 200 BC, the time of the Western Han Dynasty. Their purpose was to keep ingredients from spoiling in a time before refrigeration, but people soon discovered that the liquid leftover from making these pastes was salty and delicious and they started using it as a seasoning.

Thus, from the soy-based jiang, soy sauce was born, and from the fish jiang came its cousin fish sauce – which is pretty popular too. (There’s a meat version made in Japan called shishibishio too but it’s never hit the mainstream.)

At some point, the Japanese got wind of this fermented soy concoction and wanted a piece of the action. They did what they do best and refined the process, making it their own.

The Japanese added wheat, in equal quantities to the soybeans, resulting in a better balance to the final sauce, making it less overpowering to other ingredients. They call the mixture of wheat and soybeans koji and the final product soju, which is where the word soy comes from.

Adding wheat was so successful that the idea was taken back to China. By the 17th century there was a soy sauce similar to what we use today. The liquid seasoning spread throughout Asia and the rest of the world.

How is it made?

A modern method is acid hydrolysis, a process of breaking down soy proteins artificially, which takes just a few days. Acid hydrolysis produces a harsher and far inferior product without the subtleties of the real thing.  A lot of soy sauces sold today are made by this industrial process.

But the flavourful compounds that make proper soy sauce so delicious take time to develop – the traditional method involves fermenting soybeans and wheat slowly over many months, methods vary from producer to producer but here are the essential steps required to produce the good stuff:

  • First soybeans are rinsed several times and then boiled for around four hours until thoroughly cooked and soft. An equal amount of wheat is toasted and milled.
  • The cooked soybeans and milled wheat are mixed together and yeast is added. The mix is incubated at around 27C for 48 hours to activate the yeast.
  • The mix is then added to a brine (salt dissolved in water) which is blended to create a mash; the Japanese call it moromi.
  • The mash is fermented for several months, allowing the yeast to work its magic. It turns a reddish brown and the complex flavours develop at this stage.
  • Next, the thick slurry is strained and pressed to produce a liquid. This liquid is filtered to refine and clarify it into light soy sauce.
  • The soy sauce can be aged to develop the flavour further or enhanced with other ingredients like seaweed, mushrooms, shrimp or molasses, depending on the variety.


It’s probably fair to say that the only ingredient more universal than soy sauce is salt. But soy sauce differs in that it adds flavour to food rather than just enhancing other flavours.

Soy sauce is the staple seasoning in Asian cooking, used in wok-fired stir-fries, soups, in sauces, as a sauce, and as a general seasoning on everything savoury. It adds depth and replaces salt in slow-cooked dishes like chillis, ragus, stews and casseroles; and barbecue, pasta and meat sauces. It’s also excellent in marinades, dressings and dipping sauces.

Soy sauce is an essential ingredient in teriyaki sauce, dashi, ramen, black bean sauce; it’s a must with sushi and you can’t make char siu without it either.

It adds umami, saltiness, a slight caramel sweetness and bitterness, dark colour and depth of flavour to almost any dish across any cuisine – your imagination is the limit. The prevalence of soy sauce in global cuisine is pretty incredible when you consider the simplicity of its ingredients and production.

What makes it so good?

The rich, concentrated flavour is the result of a beautiful combination of processes.

First, there are Maillard reactions from toasting the wheat that produce savoury, slightly sweet flavours – the same as you get when you sear a steak or caramelise sugar.

Second, the build-up of acidity producing a sour taste and the development of funky aromas from fermentation.

Lastly and most important, the slow breaking down of proteins in the soy and wheat produces free amino acids; the same umami-rich doohickeys which give parmesan cheese, sundried tomatoes and dashi their unparalleled levels of irresistibility.

All of this, combined with an overriding saltiness, produces the most magical, universally applicable, dark, funky and damn tasty sauce going.

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