Explainer: Soy Sauce, Asia’s Most Important Seasoning

From the dairy section to the tinned veggie aisle, supermarkets can be confusing and overwhelming places. What’s the difference between all these similar-looking products?

Even if you can read Chinese or Japanese, that feeling gets really intense in the soy sauce section. There are various types (light, dark, thin, black, sweet), competing brands (often from different countries with different approaches), multiple grades (delineated by nitrogen concentration, with higher considered better) and even specific drawings (akin to the first and second pressings in traditional olive oil production). Here’s how to navigate it all.

Soybeans were originally domesticated in ancient China. The locals initially fermented them into an edible paste or porridge, leading to the creation of modern soy sauce about 2000 years ago. The delicious practice followed Buddhism into Korea and Japan between 300 and 700 years later. Soy sauce spread to Southeast Asia much later, in the 1600s, and is now a vital part of cuisines across the region, including Thai, Vietnamese, Filipino, Malaysian and Indonesian.

For most of history, soy sauce was made at home, or at local grocers and co-ops, much like how most European towns and villages had their own small-scale breweries and bakeries. But in a parallel with Mexico’s masa and tortilla industry, production has gradually been centralised and industrialised over the past century.

Until the early 1900s, soy sauce was only made using the process dubbed traditional, natural, brewed or fermented. This sees a grain flour like wheat, rye, millet or sorghum inoculated with aspergillus mould, known as koji in Japan. The culture is mixed with cooked soy beans, dry salt or brine, and left to ferment for several months – or several years, in the case of some artisan producers – resulting in a cascade of transformative reactions.

Enzymes in the aspergillus break the proteins and starches in the soybeans and accompanying grain down into sugars and amino acids, including glutamate, the savoury molecule that makes MSG so moreish. Two other added microbes also come into play: lactobacillus, the same bacteria found in yoghurt, ferments the newly liberated sugars into tangy lactic acid, while yeast –the same kind used in beer – creates 1–2 per cent alcohol and other tasty secondary compounds.

The turbid slurry is finally drawn, filtered and bottled for use. The slurry may be drawn four or even five separate times, with the earlier pressings the most prized for delicacy and complexity. The soy sauces available at supermarkets are also heat-pasteurised to arrest microbial activity.

In contrast, chemical or non-fermented soy sauce achieves the same result in about three days using acid hydrolysis, a widespread industrial process pioneered by Julius Maggi (yes, of Maggi noodle fame) in 1886. The soybeans are cooked with sulfuric or hydrochloric acid, which imitates the aspergillus enzymes, breaking down those proteins and starches to create hydrolised vegetable protein, long renowned for its meaty, savoury flavour, again due to glutamate.

The remaining acid is neutralised using a strong base like sodium hydroxide, creating regular salt and balancing the pH to an edible level. This kind of soy sauce is cheap to make and keeps longer than its brewed counterpart, but unsurprisingly has a simpler taste and aroma. Many products rely on this process and label themselves soy sauce, with Knorr Liquid Seasoning a notable exception. Maggi also makes a liquid seasoning, though it uses a wheat base with no soybeans.

If you’re serious about soy sauce, stick with a brand that uses the fermentation method, such as Hong Kong’s Lee Kum Kee, a venerated producer founded in 1888; Japan’s Kikkoman (1917) or Korea’s Sempio (1946). These players use just four or five ingredients: soybeans, wheat, salt, water and sometimes sugar. Other brands such as Singapore’s Ayam use the brew method but add caramel colour (E150) and extra lactic acid (E270) as a preservative. Others still, like Thailand’s Healthy Boy, may add flavour enhancers like MSG (E621) to supercharge savouriness.

If a label or recipe says “soy sauce” with no other qualifiers, it’s referring to light soy sauce. This is the most basic, all-purpose type, primarily used to make food saltier and more umami. Made from just soybeans, wheat, salt and water, it’s suitable for marinading, dipping, stir-frying and dressing. It has a complex, delicate flavour due to being made from earlier draws of the soybean slurry. Use liberally.

A concentrated light soy sauce. During production, soy sauce is added in place of the brine prior to fermentation, resulting in a stronger, more complex flavour, but no extra salt. This makes it ideal for finishing dishes or dipping, where just adding more soy sauce isn’t always feasible.

Dark soy is mainly a cooking ingredient used to add colour and a hint of sweetness to braises, stews and stir-fries, often in concert with light soy sauce. It’s sweeter and less salty, with 10–30 per cent added sugar, and sometimes cornstarch for thickening. It’s made from later draws and aged longer, giving it a simpler, more robust taste. Use sparingly and don’t be tempted to sub it in place of light soy. (Confusingly, this light/dark logic is inverted in Japanese cuisine – dark soy is the default, “regular” style, though still used for cooking rather than dipping, dressing or finishing dishes.)

Sweet soy, or kecap manis in Indonesia, is used heavily in Southeast Asian cuisines, where dishes are often judged on their balance of sweet, sour, salt and spice. It contains 50–70 per cent added sugar, traditionally in the form of coconut sugar or jaggery. Earthy spices such as star anise, clove, coriander seed, cinnamon and pepper are often added too.

At 80–90 per cent sugar, karamel masakan (to use the Indonesian term) is the sweetest product in this category and sometimes doesn’t contain any soy at all. As the name suggests, the sugars have been caramelised, giving it a deeper, toastier character.

Miso, Japan’s famous fermented soybean paste, is mostly made the same way as soy sauce, albeit without wheat. Tamari was originally a byproduct but has since become a prized soy sauce in its own right. It’s often gluten-free, but not always, so check the label to make sure. The lack of wheat and higher soybean content gives it an intense flavour and slightly thicker body. In a pinch, you can use it in place of soy sauce, though the taste is noticeably different.

As some brands add MSG to boost umami, others use mushroom extract, another rich source of glutamates. Some brands even use both. Other specialty soy sauces can include fish sauce or shrimp paste to complement seafood dishes.

If you’re cooking a particular cuisine, a soy sauce from the corresponding country will give the exact taste you’re looking for. Using one from a different country isn’t wrong, or likely to compromise the finished dish in any real way. You’ll just get a slightly different taste. The most important thing is using the correct type of soy – light, dark, et cetera – the recipe calls for.

China’s vast population, with its patchwork of dialects and regional cuisines, means soy sauce that’s more diverse and less codified than those from other countries. That said, Australian shelves are dominated by southern/Cantonese sauces, due to the majority of immigrants throughout the 20th century hailing from there. Expect a relatively low wheat content, and a stronger, more robust flavour.

The Chinese government groups soy sauces into four grades, based on nitrogen concentration. Then there’s the first drawing, second drawing, et cetera. All these terms are hard to translate, which is why brands like Lee Kum Kee may have confusing sub-titles like Gold Label or Premium. Choose the more expensive option if you’re keen on something higher quality.

As you’d expect from a country famous for devoted craftsmanship, Japanese shoyu is rigorously categorised into five types: koikuchi (dark), usukuchi (light), saishikomi (twice fermented), shiro (white) and tamari. The Japanese pioneered the use of defatted soybeans (i.e. soybean meal with the oil removed) in order to speed up production, and today this is the standard across most Japanese brands. Look for the more expensive marudaizu (“whole soybean”) shoyu if you’re after a more complex, delicate flavour than regular koikuchi soy sauce.

In general, the Japanese favour a 50/50 mix of soybeans and wheat, making for slightly sweeter, less intense soy sauces. This middle-of-the-road standard explains the existence of the two other extremes: tamari (containing little to no wheat) and the exceptionally mild shiro (about 90 per cent wheat), which is used to season clear soups and white fish without imparting too much colour and flavour. As in China, there are three legally defined grades of soy sauce, pegged to nitrogen concentration.

The traditional Korean process for fermenting soybeans is distinct from the traditional Chinese and Japanese methods. The beans were soaked, boiled and ground, then compacted into a brick for drying. Once hardened, the bricks were tied in rice straw (which contains natural microbes) and left to ferment. Afterwards, the bricks were placed in earthenware crocks and submerged in brine to age. The liquid was then strained to become ganjang, while the solids were mashed into doenjang (soybean paste, or Korea’s answer to miso).

There are three main types of ganjang. Joseon, also known as guk-ganjang or soup soy sauce, is a fermented all-purpose soy sauce with an intense flavour. The lighter, sweeter yangjo is Korea’s version of dark soy, used to marinate meats and add colour. It’s naturally brewed with some wheat, a hangover from Japan’s 35-year occupation of Korea. The third type, jin ganjang, is chemical soy sauce made from hydrolysed soy protein.

There are small differences between soy sauces produced in Thailand, Vietnam, Indonesia, Malaysia, the Philippines and their neighbours. But for the sake of brevity, it’s easiest to generalise. Compared to their East Asian counterparts, the Southeast Asian brands in Australian supermarkets are more likely to be produced chemically and use additives like sugar, colour and MSG. Brands like Malaysia’s Yuen Chun are the exception, typically made in countries where a large Chinese diaspora has hung onto its original cultural identity, including a traditional approach to making soy sauce.