An In-Depth Look At Soy Sauce, Asia’s Favourite Condiment

6 Mins Read

On a Twitter thread (where all intellectual conversations begin, naturellement) where fellow food writer Clarissa Wei lamented the fact that so little has been written in English about East Asian soybean-based sauces, I chimed in with a thought about the lack of talk about variation in soy sauce fermentation methods and their resulting flavours and usages.

From this thread spawned some interesting resources from other fellow food nerds, such as the Kikkoman Food Culture Journals, recommended by The Joy of Cooking (still a bit starstruck that they tweeted me), which is such a delightful trove of English-language writing on Japanese food culture. In the first few issues, there’s a detailed history of soy sauce in Japan. I love how the writer, food historian Ryoichi Iino, kicks off the series:

We need soy sauce just like we need air and water – and like air and water, we take its availability for granted. 

It’s so true – despite being a Cantonese person who’s had soy sauce all her life, I’d never, until fairly recently, thought about how this essential condiment is made, and what’s required to make a good one. I’ve read very few meaningful articles in mainstream English-language media (actually, even Chinese) about soy sauce science. These questions began answering themselves when I visited a couple of Chinese sauce factories as part of some columns I wrote for the SCMP back in the day. 

Generally speaking, most soy sauces are made by taking a soy bean and wheat flour (or barley) mixture, and inoculating it with a starter mould (a.k.a koji (why are Japanese terms so much more widely used in the West for these things? A topic worth researching…) which creates enzymes, thereby breaking down the soy and wheat). Then either brine (salt and water) or just salt is added. The amount of water determines whether the mixture ferments in a liquid or solid state. To my knowledge, Yuan’s is the only soy sauce maker in Hong Kong that uses solid state fermentation (SSF), and unlike some other solid state methods that include a small volume of water, Yuan’s uses no water at all. According to the owner, when I interviewed him back in 2017, this completely water-free solid state soy sauce is a Fujian thing, whereas liquid state fermentation (LSF) is common for Cantonese soy sauces. To my knowledge, Japanese and Korean soy sauces are also liquid state. 

The differences, just from my own anecdotal experience, are evident in every way – colour, viscosity and flavour. SSF soy sauce from Yuan’s is extremely dark and inky, with a mushroomy flavour, is less salty, and is very thick. (I’ve yet to try an SSF soy sauce by anyone else – it seems rare, but I do wonder if places with high Fujianese populations, eg. Malaysia, do it). Artisanal LSF soy sauces made in Hong Kong, such as Kowloon Soy, Pat Chun, Koon Chun, and Dai Ma have a slightly sweeter, fruitier (sometimes alcohol) flavour, and tend to be less thick, although still quite inky compared to commercial soy sauces (like Lee Kum Kee – who claim to use natural fermentation methods even though the flavour, apart from the Double Deluxe, can’t hold a candle to the ones just mentioned – but I haven’t been able to find out much about their soy sauce processes, so, no comment!). I’ve read some scientific journals explaining the flavour differences between SSF and LSF soy sauces, and more than one has come to the conclusion that SSF produces fewer aromatic compounds. Wouldn’t more aromas be better? Why do some makers insist on SSF then, especially as it’s so expensive to make? I don’t exactly know why yet, but my guess is that having more aromas might not be the only point – maybe the specific aromas created by SSF, though fewer, are more distinctive and delicious?

The “traditional” way of brewing soy sauce allows nature to do its work – heat from the sun and time allow enzymes to break the mixture down. Soy beans are protein-rich, and protein is made up of blocks of amino acids. Breaking these blocks apart releases the individual amino acids, one of which is glutamic acid (together with sodium, it makes MSG), so that explains why soy sauce is such an important condiment – it provides what we now call umami (うま味 in Japanese; in Chinese we use the word 鮮 sin (Canto)/xian (Mandarin) which can also mean fresh), the “fifth” taste. 

Apart from protein, there are also carbohydrates and fats in the soy and wheat mixture, and they get broken down by the enzymes too, which creates the rich, layered flavours – earthiness, sweetness, a waxy “oily” mouthfeel, etc. that characterise a good soy sauce.

Like any fermented product, industrial soy sauce has much less complexity. A common industrial method yields “chemical” soy sauce, where hydrochloric acid instead of fermentation is relied upon to break up the soy proteins. Whole soybeans in traditional soy sauce are foregone for soybean residue, leftover from soybean oil manufacturing (which is known as “defatted” soy meal and written on ingredient labels as “hydrolysed soy protein”); its relative lack of depth and colour made up for with additives like corn syrup, and colouring. 

Sidebar 1: Soy sauce and gluten

Tamari is a Japanese-style soy sauce with no wheat added, and has become popular with the gluten-free crowd. It tends to be less full-bodied and have less natural sweetness, but has tons of umami.

Chinese soy sauces tend to use less wheat than Japanese ones. While I wouldn’t recommend it for anyone with celiac disease, if you’re desperate for soy sauce (and can’t find GF soy sauce/tamari) and have mild gluten intolerance, you might have a better chance with an artisanal Chinese soy sauce (especially SSF, but it’s hard to know that) over a Japanese one. If gluten intolerance is an issue, apart from tamari and liquid aminos, there are other products like black soybean sauce that are also good substitutes. (I swear this isn’t a Pat Chun advertorial, I just love their stuff because they’ve used so much time and effort to create additive-free, diet-inclusive foods and sauces using or inspired by traditional methods, with accountable new-school processes, and they’re 100% made in Hong Kong.)

Sidebar 2: Types of Chinese soy sauce

This isn’t an exhaustive list, but just some of the common and/or interesting types you might find at the shops in Hong Kong.

Chinese dark soy sauce (lo chau 老抽) is made by adding caramel to regular soy sauce, and in Chinese cooking, is usually used when you want a darker colour, eg. for soy sauce chicken. Thick “black soy sauce” or kecap manis, made in Southeast Asian countries, is similar, but usually sweetened with sugar, and sometimes contains herbs and spices.

The first/original batch of soy sauce taken from the fermentation tanks is called tau chau 頭抽 in Cantonese. Once the first batch is removed, brine can be added to the leftover fermented soybean-wheat combination to brew a second, less intense soy sauce, which is usually cheaper and used in cooking; whereas the rich tau chau is usually used as a dipping/dressing.

Sheung Wong Sang Chau 雙璜生抽 is often translated as “double deluxe” and deluxe it certainly is. It’s basically twice-fermented soy sauce – you take tau chau, and ferment it again with a new batch of inoculated soy and wheat. That’s double the amount of soy beans and wheat, and almost double the time. It has a much higher glutamate-to-salt ratio, which technically means it has better umami, hence it’s great as a dipping sauce and a very indulgent soy sauce to cook with. It’s like the méthode champenoise of soy sauces (you can totally quote me on that, LOL), but not in-bottle.

Not really a sidebar: Soy sauce history rant

Like anything that’s been around for millennia, it’s unclear where soy sauce comes from. Some prevailing theories say it was a byproduct of soy bean paste (eg. miso, again, the Japanese term is most widely accepted in English…) while others say soybeans were added to fish to aid in the fermentation of what we now know as fish sauce. The headline in this SCMP article on fish sauce is super annoying in that it assumes fish sauce came from the Roman Empire to Asia via the Silk Road, whereas the article itself actually says there’s no real evidence either way, and its sources say it could have been developed independently in Rome and Asia. The earliest writings in both China and the Roman Empire about fermented fish/soy sauces are from around the first century AD – why does English-language writing always assume Europe was first? Ugh!

This article was first published on Janice Leung Hayes’ Soy Much To Talk About in her e-ting newsletter, it is republished here with the author’s permission.

Lead image courtesy of Snuk Foods.


  • Janice Leung Hayes

    For the past 15 years, ex-Melburnian Janice Leung Hayes has been writing and learning about food in her birthplace of Hong Kong. She has written, spoken and produced multimedia work on the subjects of food, luxury travel, media and social entrepreneurship in such publications as Condé Nast Traveler, New York Times, Monocle and Eater. You can find her on Instagram and Twitter at @e_tingand subscribe to her e-ting newsletter, which features her take on trends and food culture with a decidedly Asian POV, as well as reading recommendations and more. Under her food sustainability platform Honestly Green, Janice also organizes popular food & farmers' markets across Hong Kong.

You might also like