Naturally Fermented Soy Sauce: Flavour, Patience, and a Night I Remember
Why I choose carefully—and what a bottle's label can tell us
Emperor Hirohito, also known as Emperor Shōwa, visited Belgium in 1971 during the reign of King Baudouin.[10] That visit provides the historical setting for a night I remember from my work in airline catering in Belgium, when I had the opportunity to talk through the night with the Emperor's cook.
He was already an elderly man. Our conversation left me with a lasting interest in the quality of Japanese food, particularly soy sauce.
I remember him telling me that Kikkoman's naturally fermented soy sauce was made exclusively for the Imperial Court. That is my recollection of his words, rather than a verified statement about the company's entire range.
There is a real historical connection: Kikkoman records that its Goyogura brewery was built in 1939 to preserve traditional techniques and continue supplying the Imperial Household.[1] However, naturally brewed Kikkoman soy sauce also has a long commercial history. It was not a process reserved solely for the court.[2]
Perhaps he was describing a special imperial preparation. After all these years, I cannot know exactly what he meant. What stayed with me was his respect for patient fermentation.
What does “naturally fermented” mean?
Traditional soy sauce develops its flavour through fermentation rather than relying solely on a rapid breakdown of protein.
In Japanese brewing, soybeans and wheat are prepared and cultured with koji mould. The resulting koji is mixed with salt water to form a mash called moromi. Fermentation and maturation develop its complex flavour before pressing and finishing.[3]
Thai and other Asian traditions use their own recipes and methods. Some use different grains, so Japanese-style ingredients should not be assumed for every sauce.
The characteristic savouriness is called umami. Fermentation releases glutamate and develops other flavour compounds. This is why a naturally brewed sauce can have a rich taste without added MSG.
“No added MSG” does not mean “no glutamate”: naturally occurring glutamate is part of the flavour.
My favourite Thai sauce
Living in Thailand, I enjoy finding locally made seasonings. My favourite is Sun Chaw Wong Gold light soy sauce, a Thai product.
The bottle's ingredient list names water, soybeans, salt, and wheat flour, with no sugar listed. Its label states that it contains no added MSG, no artificial colour, no preservatives, and non-GMO raw materials. It also carries the manufacturer's claim “safe from 3-MCPD.” These are label declarations, rather than independent laboratory verification.
The maker's product page describes Gold as naturally brewed for more than six months.[8] I had remembered nine months, but the information checked here supports the more-than-six-month description.
The label warns that it contains soybeans and wheat flour, so it is not suitable for someone avoiding wheat or gluten. It also instructs users to refrigerate after opening.
For me, the attraction is a sauce with a good flavour and a clear recipe. I want it to complement the food, rather than overwhelm it.
Fermented sauce and hydrolysed seasoning are different
Acid-hydrolysed vegetable protein can also be used to make savoury sauces. This process breaks down protein with acid and can be much faster than traditional fermentation. Some products combine fermented sauce and hydrolysed ingredients.
| What to check | Why it matters |
|---|---|
| “Naturally brewed” or “naturally fermented” | Describes the production method |
| Ingredient list | Shows whether sugar, flavour enhancers, or hydrolysed protein are added |
| Sodium per serving | Helps you judge the amount of salt you are using |
| Wheat and other allergens | Ordinary soy sauce often contains wheat as well as soy |
| Exact product name | “Light,” “dark,” and “seasoning sauce” are not interchangeable |
| Storage instructions | Tell you how to maintain quality after opening |
“No added sugar” is different from a laboratory finding of zero sugars. Likewise, non-GMO ingredients reflect a production choice; they do not by themselves prove that one sauce is healthier or free of contaminants.
What about the cancer warning and Australia?
I had heard that Vietnamese soy sauce was carcinogenic and could not be imported into Australia. That statement needs more care than a country's name.
A genuine food-safety issue has involved chloropropanols such as 3-MCPD and 1,3-DCP. These contaminants can form during acid hydrolysis of vegetable protein under certain conditions.[4] Historical Australian assessments investigated their occurrence in soy and related sauces and the potential health risks.[5]
This is a question of processing, contamination levels, and exposure—not evidence that all Vietnamese soy sauce causes cancer.
Australia's imported-food controls prevent noncompliant food from being distributed for sale.[6] A failed consignment or recalled product does not establish a permanent ban on every soy sauce from its country of origin.
I have not verified a current blanket Australian ban on Vietnamese soy sauce. Without a specific product and an official notice, I would not publish that claim.
Choosing a reputable producer and a clearly identified product is more useful than judging safety by nationality alone. Natural fermentation is also not a guarantee that a product has passed every safety test.
Health value: seasoning, not a supplement
Soy sauce is useful for flavour, but the small quantity used should not be counted as a major protein source or a treatment for disease.
The everyday concern is sodium. “Naturally brewed,” “non-GMO,” and “no added sugar” do not mean low-salt. WHO recommends adults consume less than 2,000 mg sodium a day, equivalent to less than 5 g salt.[7]
Use soy sauce to replace some other salt in the meal. Measuring a teaspoon is more helpful than pouring freely from the bottle.
Many bottled sauces are heat-treated, so fermentation does not automatically make them sources of live probiotic organisms.
Simple ways to use it
For a vegetable stir-fry, start with one teaspoon for two servings and taste before adding more.
For tofu or tempeh, mix two teaspoons soy sauce with one tablespoon lime juice, one tablespoon water, grated ginger, and crushed garlic. Coat, refrigerate briefly, then cook.
For a dipping sauce, dilute one teaspoon soy sauce with two teaspoons water and add lime, chilli, and spring onion. Dilution spreads the flavour; it does not remove the sodium if you consume the entire mixture.
Store the bottle according to its instructions and use clean utensils.
What I still remember
That conversation in the catering kitchen gave me something more enduring than a brand recommendation: an appreciation for ingredients that take time.
Today, I can enjoy that idea in my own kitchen in Thailand. A little good soy sauce can make ordinary vegetables, tofu, or brown rice taste more interesting. The pleasure is in the flavour—and in understanding what is actually in the bottle.
Sources
- Kikkoman: Company history, including Goyogura
- Kikkoman: Soy Sauce Business
- Kikkoman: Making Soy Sauce
- Research paper: Analysis of 3-MCPD and 1,3-DCP in Asian-style sauces
- ANZFA: Historical assessment of chloropropanols in sauces
- Australian Department of Agriculture: Imported-food noncompliance report and controls
- WHO: Sodium reduction
- Sun Chaw Wong: Manufacturer product range
- Product-label photographs supplied by the author on 5 October 2026: ingredient, allergen, storage, and product declarations.
- Belgian Monarchy: King Philippe's state-banquet speech, 23 June 2026, confirming Emperor Shōwa's 1971 state visit to Belgium.
Draft for HealthyRetired.com. The catering encounter is the author's personal recollection. Product-label declarations are identified as such; they are not independent test results.