The invention of soy sauce, with its intensely salty and umami-rich properties, was a classic case of necessity-being-the-mother-of-invention. Salt was historically an expensive commodity, so, in order to make salt go further, innovating Chinese cooks fermented fish with salt, and the resulting paste was used to add a salty element to dishes.
Over time, fish was replaced with soybeans, and around 2200 years ago, the soy sauce as we know and love today was created. It spread through other Asian countries as a condiment and a seasoning, adapted along the way to local palates and cuisines.
In the 7th century, soy sauce made its way to Japan, where it became one of the essential components of Japanese cooking.
"Soy sauce is the most common seasoning in Japanese food. It's just like salt in Western cooking," says Justine Schofield, host of Justine's Flavours of Fuji, who visits Meijiya, a 120-year-old soy sauce brewery in Shizuoka, Japan, to learn about the brewing process.
The briny umber liquid, one most of us don't give a second thought when adding it to stir-frys or pouring it into a bowl for dipping sushi, actually takes years of work to produce. That is, unless it's a fake, where it only takes a few days to brew the imposter concoction of salt, water, some protein extract, flavour enhancers and colouring.
The real deal is brewed in a similar way to beer, which is made by fermenting and maturing a "mash" of grains and yeast. Sixth-generation soy sauce brewer at Meijiya, Shohei, explains that soy sauce starts with a giant cauldron of soybeans. These are steamed, then combined with roasted wheat and Aspergillus mold, and aged for several days to produce koji. This koji is then combined with salt and water and aged for 1-3 years, with the resulting sludgy, brown porridge-like mixture known as "moromi".
"The maturation of the moromi determines how rich the flavour of the soy sauce will be," says Justine.
"The moromi is then squeezed through 300 pieces of fabric to produce the soy sauce."
The result of this ancient craft is a rich, complex liquid that is one of the five foundations of Japanese cuisine, which is rememberd by the cute mnemonic "sa-shi-su-se-so", where "sa" is "satou", sugar; "shi" is "shio", salt; "su" is vinegar; "se" is "seuyu" (the antiquated word for shoyu, soy sauce in Japanese); and "so" is miso.
Soy sauce is used in Japan for everything from dipping sauces for sushi and tempura to adding flavouring the broths for soba, udon and ramen—"shoyu ramen" is one of the most popular of the cult-classic bowls.
There's also lesser-known and less-conventional uses for soy sauce: adding it to meat sauces to boost umami (even bolognese), soy sauce soft serve, seasoning omelettes, making a sweet glaze for rice dumplings and puddings, and for curing—"shoyuzuke" (soy sauce-pickled) is used commonly for tuna and salmon as a sushi topping, ikura is cured salmon roe, and even slices of avocado or cream cheese are cured in soy sauce to serve as a savoury snack accompanying sake.
The main variety of Japanese soy sauce you'll encounter inside and outside Japan is koikuchi (dark). It's known for its deep colour, rich soy sauce-flavour and mild sweetness. The other variety, usukuchi (light) may be lighter in colour, but is 15% saltier. It's traditionally associated with Kyoto cuisine, as it didn't taint the delicate colour of dishes of the area's haute cuisine served to the upper echelons of society.
Aside from these two main varieties, there's also tamari, which is all soybeans (no wheat), and deeper and richer in flavour; it's popular for sashimi, and is good for those with gluten intolerances. And "white" soy sauce, which is not white but definitely lighter than other varieties—amber-ish in colour; it's made with a high wheat proportion and has a sweeter flavour. There's even some interesting modern creations like flavoured soy sauce, and soy sauce aged in whisky barrels.
If you're visiting Shizuoka and keen for a glimpse into the craft of soy sauce-brewing, Meijiya brewery is open to the public, where visitors can do a tour of the brewery and a hands-on soy sauce-making experience.
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