The earliest indication of the existence of something akin to soy sauce was a mention in Chinese writings in 150 AD of a fermented black soybean extract called “shizhi” used in a recipe for a meat marinade.
This was followed in 160 AD by a description of “qingjiang” or a sauce made with “jiang”, a word used to describe various foods pickled with salt – these include fruits, vegetables, seaweed, meat, fish and various grains (including rice, wheat and soybeans).
Apparently, one type of jiang is called “modu”, which is a fermented salted soy paste. Even today, the Mandarin word for soy sauce is “jiangyou” (or “the liquid extracted from jiang”).
There were many other names for various sauces in the following decades and perhaps the most telling was “chiyou” – which is translated as the “liquid extracted from soy nuggets”.
The word “chiyou” is plausible as the origin of the Cantonese word for soy sauce, which is “shi-yau”, and from that, it is a short hop to the Japanese “shoyu” where the earliest mention of soy sauce in the country was shoyu being given to a Buddhist monk in the year 1568 – therefore presumably, soy sauce was introduced earlier sometime in the late 15th or early 16th century.
Over a thousand years before then, in 544 AD, the world’s earliest encyclopaedia of agriculture was published in China – and in it was a description of the fermentation of soy sauce.
History then indicated that the ingredients for soy sauce in China varied through the centuries, with assorted types made with soybeans blended with wheat or barley before finally settling on using pretty much only soybeans by the 19th century.
However, since its introduction to the country, the Japanese had adopted a more cautious, conservative strategy to the craft of making shoyu, refining the recipes and ingredients carefully until they ended up with the classical types of Japanese soy sauce today.
The first ever export of soy sauce to the West was in 1647 from Nagasaki, Japan, via the Dutch East India Company – and it is notable that just over 30 years later, by 1679 the English philosopher John Locke was already noting in his journals that saio (shoyu) was a sauce from the East Indies.
The types in China and Japan
Modern Chinese fermented soy sauces generally come only in two types: dark or light, and this is more or less a simple reflection of the darkness and density of the sauces.
Japanese soy sauces have some further official grades or types – actually five in total. Most Japanese soy sauces are graded as “koikuchi” – this grade is what is generally simply called shoyu and accounts for some 56% of the annual soy sauce production in Japan.
Koikuchi soy sauce has a pleasant aroma, interesting flavours and is deep reddish brown in colour – and it will introduce a distinctive umami flavour to food due to its high glutamic acid content.
A higher grade of soy sauce is “usukuchi shoyu” – this is a lighter reddish brown sauce with a milder aroma, lighter taste, and is generally used when cooks do not wish the soy sauce to cloud over the subtle flavours of other food ingredients. Around 24% of Japanese soy sauces are of this grade.
There is also another grade or type called “tamari shoyu”, made like Chinese soy sauce from wholly or almost solely soybeans – with very little wheat added, if any. This rather dense sauce tends to lack any depth of aroma and accounts for 8% of Japanese production. It is fermented by Aspergillus tamari and is often used as a glazing component of teriyaki dishes and rice cakes.
An interesting type of Japanese soy sauce is “saishikomi shoyu” or re-fermented soy sauce. The production method of this type of soy sauce uses another soy sauce instead of brine for the fermentation, resulting in a densely coloured sauce with a stronger flavour and aroma. It is also significantly sweeter and is often seen applied on sashimi or nigiri rolls in sushi restaurants.
The least commonly produced and somewhat unusual Japanese soy sauce is “shiro shoyu”. This is the palest-coloured sauce, with a rather tame flavour but it has interesting aromas and sweetness. It is mostly used in soups and a famous steamed egg custard dish called chawanmushi.
All the five above-mentioned Japanese soy sauces comply with the JAS (Japanese Agricultural Standard) for soy sauce, though there are many variations which are not JAS-certified, such as dashi soy (dashi-flavoured soy sauce), tare (spiced and sugared soy sauce used for basting), ponzu (soy sauce mixed with citrus juices or vinegars), et cetera.
Soy sauce and alcohol – not possible to get drunk
Note that all fermented soy sauce always contains a small amount of alcohol, normally varying between one to 4.5% by volume – but it is practically impossible to get drunk on soy sauce because it is highly improbable the body is able to swallow enough due to its strong saltiness.
Without the existence of the Aspergillus moulds, in particular Aspergillus oryzae and Aspergillus sojae, food would simply taste radically different for billions of people on the planet.
The actions of these moulds on mashy mounds of cooked soybeans (and wheat) are like a filamentous (fungal) symphony – the biological harmony is adeptly tuned to the fermentation environment and is exceptionally efficient.
It is no exaggeration to state that the direct and indirect outputs from the Aspergillus moulds have profoundly coloured human dietary preferences and have had a major influence on the ways people produce, prepare and cook our food for almost 2,000 years.
Soybeans, like a few other legumes, are interesting in that they have a high proportion of nitrogen (held as proteins) in the seeds. With soybeans, it is due to the plant having a curious symbiotic relationship with a bacterium called N-fixing rhizobia which helps to convert nitrogen from the atmosphere into ammonia.
This ammonia is then used to build amino acids which are then linked together to form the proteins in soybeans. For a legume, the protein content of soybeans is very high; over 36% by weight of dry soybeans, with another 30% carbohydrates and 20% oil.
In fact, soybeans plants are probably the most efficient method to produce proteins when measured in terms of land usage.
This combination of high protein and high carbohydrate content in soybeans makes koji mash an ideal environment for Aspergillus moulds. These fungi start their work by producing enzymes to digest the koji mash – this process is made more fascinating by how Aspergillus produces enzymes to match its environment.
An interesting paper written in 1952 by Crewther and Lennox describes a sequence of enzymes produced by Aspergillus oryzae, though it must be noted their analysis covered enzyme production in a non-soybean culture medium (a protein-free sucrose-tartrate solution), at a lower temperature and for a longer time horizon.
Still, it is an intriguing piece of research as it documented that Aspergillus oryzae commenced its digestive sequence in a sucrose-laden solution with the production of sucrase, amylase, then followed by esterase and a couple of proteases.
Other more recent papers on the effect of the same mould on koji mash in a soy sauce production environment indicate that Aspergillus oryzae is very flexible, for different types of enzymes were produced to digest the soybean content in the tests.
In koji mash, the same mould produced a neutral protease, followed by amylase and then by an alkaline protease. Unlike the 1952 study, no sucrase is detected in the fermentation of koji mash.
Curiously, the enzymatic activity was found to follow a slightly different pattern from the production phases of the enzymes. The neutral protease was most active at 48 hours, while amylase and the alkaline protease were much more active at the end of the fermentation period of 72 hours though both were not as active as the neutral protease at its peak.
In effect, the primary digestive focus of Aspergillus oryzae on soybeans is the cleaving (digestion) of proteins into peptides (via the proteases), followed by the decomposition of carbohydrates into simple sugars (via amylase). This all occurs during the 72 hours for the preparation of koji mash for brine fermentation.
During brine fermentation, the continued action of the Aspergillus oryzae proteases breaks down further some of the peptides into amino acids, and a proportion of these amino acids will bind with the simple sugars cleaved by amylase from the soybean starches to form dark brown melanoidins due to the Maillard reaction.
The proteases act very slowly as the environment created by pediococcus halophilus during brine fermentation is mildly acidic and not wholly suited for the neutral and alkaline proteases released by Aspergillus oryzae – however time is not really a problem as the brine fermentation stage runs for months.
Pasteurised or not?
Like many foods, most soy sauces are pasteurised before bottling – the simple reason is that the heat process would kill off pathogenic bacteria and this helps pasteurised food stay edible for longer.
The downside is that other nutrients such as vitamins are also lost or diminished during pasteurisation – and the heat also destroys the proteases and enzymes in fermented soy sauces.
Due to the strong proteolytic (enzymatic decomposition) action of the Aspergillus oryzae proteases on proteins, plus their ability to function in a salty environment, it is not a surprise to find research papers on the use of Aspergillus oryzae proteases in the preparation of fish sauce.
In fact, it is quite highly probable that some of these proteases are already in use for making anchovy and fish sauces though one can never be sure as the blends of proteases used in the food industry are usually tightly guarded secrets.
In any case, the interesting fact is that unpasteurised soy sauces contain active proteases and such enzymes are very useful for tenderising meat quickly. And that is why unfermented soy sauces work so well in BBQ sauces, for not only do they impart the pleasant salty umami flavours that meat lovers enjoy, but they also play a significant role in softening the textures of meat.
To be honest, I had not known this for years as I would just buy different varieties of expensive soy sauces to try them and some of them were labelled with the words “nama shoyu”. I was curious and wanted to know the results of cooking with the best quality sauces (as by then I was no longer an impoverished student and seriously wanted to compensate for the bad cooking days in my youth).
It was not until later that I realised that “nama shoyu” just means unpasteurised soy sauce and I found that these sauces work really well in preparing BBQ marinades that can effectively infuse and tenderise meats within a short period of time.
The BBQ marinade
So here is one of my favourite and simplest BBQ marinades, using an unpasteurised koikuchi sauce as the base ingredient. This marinade works best for around 1 kg of beef steak, pork or chicken quarters – if you need more, simply multiply quantities by the kilos of meat you want to cook.
100ml unpasteurised soy sauce
20ml cold water
20ml tomato ketchup
20ml virgin olive oil
1 tsp crushed garlic
1 tsp ground black pepper
1 tsp finely chopped oregano (or sage for pork, or herbes de Provence for chicken)
1 tsp honey (optional, depending on your mood and taste preference – in fact, you can use 2 teaspoons if you like honey-flavoured meats, but please do not use honey with beef)
Mix all the ingredients together well and rub over the meat in a deep dish. A better suggestion is to put the meat in a food-quality bag, pour in the marinade on both sides, squeeze out the air before sealing and massage the bag to get the meat fully coated with the marinade.
Leave for 2-3 hours in the warmest (usually the highest) rack in the refrigerator, turning every hour or so – and then barbeque on medium heat, flipping over every few minutes. When the meat looks reasonably cooked, use a quick-read meat thermometer to check the internal temperature of the meat at its thickest, meatiest part is as follows. If so, remove from the grill and leave to rest for the suggested periods:
– 55°C for rare steak, 60°C for medium rare or 65°C for medium beef steak – followed by 3 to 5 minutes resting time for rare steak, 1 to 2 minutes for more cooked steak
– 70°C for chicken followed by 3 to 5 minutes resting time
– 62°C for pork, followed by 3 to 5 minutes resting time
The resting times are not only to prevent mouth burns – the resting period is also useful for killing off any residual bacteria without more heat overcooking and drying the flesh.
For example, the official safe temperature for cooked chicken is actually 74°C but in fact, all pathogenic bacteria in chicken would also be killed off if the internal temperature is maintained at 62°C for a minimum period of 12 minutes in every part of the chicken – note it is quite important that all parts of the chicken are at this temperature for the minimum period.
This is because heat kills bacteria, not temperature – and if you are curious about this statement, it is explained here.
At this point a little warning would be in order: If you leave the meat too long in the marinade (eg. over 24 hours), the proteases in unpasteurised soy sauce can profoundly change the structure of the meat proteins.
Some people might like this and some people might not – for example, in certain restaurants, the red roasted pork “char siu” is sometimes tenderised significantly during preparation, resulting in a rather soft texture – so be prepared for something a bit different if the above marinade is left too long on meats.
You should bear in mind that modern proteases (some of which are probably derived from Aspergillus oryzae activity on soybeans) are potent proteolytic compounds; for example, these enzymes can ferment fish sauce in just a few short weeks while such fish fermentation in a natural environment would take around three years.
The above marinade would also work if pasteurised soy sauce is used – in which case the meats can be left in the marinade for longer, perhaps even 1 or 2 days.
The downsides are: (i) the taste is a touch less refined, and (ii) the meat tends to get too salty so perhaps use less soy sauce and more water to reduce over-saltiness.
You are now earnestly encouraged to create your own variations of BBQ sauces to suit your tastes. My neighbour enjoys using five-spice powder in his marinades, a German ex-colleague includes an interesting blend of calvados and honey – and I have another variation that uses brandy or whisky, ginger and molasses in a marinade for pork ribs.
All these recipes have in common is the use of soy sauce as the base ingredient – and as mentioned, if you really cannot get unpasteurised soy sauces, then you can use good fermented soy sauces and just leave the meats to marinade longer in the refrigerator.
A final caution
While researching this article, I came across several papers which suggest that one can make fermented soy sauces at home. This looks interesting as a little project which can provide an unusual sub-feature to include – but on deeper inspection, the risks are just too high.
There is no certainty that I will obtain the right Aspergillus moulds in my cultures (especially as I live in a remote part of France), and if I did not, then all I would be cultivating is an unknown blend of bacterial and fungal gunk – and more worryingly, it might introduce aspergillosis or some airborne disease to my little dog at home (as he already has a mild but chronic respiratory condition).
So, fun as it seemed originally, I had to settle in the end with opening another bottle of claret to enjoy with a juicy piece of beef at a recent garden BBQ.
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