If you’ve cooked with me or joined one of my dumpling classes, you know I’m obsessed with good soy sauce. Not the mass-market stuff you find in plastic bottles at the grocery store — I mean the deep, fragrant, naturally brewed Taiwanese soy sauces that have been perfected over generations.

In December 2024, I spent a week traveling across Taiwan visiting small, medium, and large-scale soy sauce producers. What I found was a fascinating blend of old-school craftsmanship and modern precision, with every maker fiercely proud of their methods. Here’s everything I learned about how authentic Taiwanese soy sauce is made.

The Basics of How Soy Sauce is Made 

Whether they’re a large, medium or small batch producer, all the companies I visited use a similar overall method of making soy sauce: 

Boil soybeans, wash them, inoculate them with koji (rice or vegetable yeast).

1. Let them ferment for min 3, max 7 days

2. Wash the koji off the bean and put it into a barrel

3. For a wet fermentation, add salt and water. For dry fermentation, which gives fragrance rather than flavor, add only salt

4. Cover with a layer of salt to prevent oxygen exchange and too much evaporation

5. Open 180 days to 2 years to press and extract the sauce. Boil again and mix with sugar for flavor

6. Bottle, pasteurize, and label

Though all soy sauces I observed were made this way, the final products tasted very different. Let's see how production can affect taste.

Medium-Scale Production: O’Long 黑龍

Located in Minxiong, an hour north of Tainan, O’Long produces soy sauce using a highly controlled, modernized fermentation process while sticking to traditional Taiwanese ingredients: black soybeans, salt, water, and a touch of sugar. 

O’Long is proud of their mechanized, precise and modern methods, which allows for them to get the best possible fermentation out of the soybeans. 

The soybeans are inoculated with the koji rice yeast - that is, the yeast is spread on top of the steamed soybeans, and they are laid out to ferment for 7 days in various temperature-controlled fermentation rooms. 

There are five separate rooms at different temperatures, ranging from 30-36.8C, depending on the stage of the fermentation process. After spending a day or two in a room, the soybeans are moved to a cooler room to continue fermenting. Air circulates throughout the rooms to ensure airflow and even fermentation.

In contrast to artisan soy sauce, where they go by “feeling of the air,” every part of the fermentation process is temperature controlled and monitored. And, instead of the standard 3 days, they ferment for 7 days, which allows for the koji to penetrate to the center of the bean, giving it more depth of flavor. According to James, all the flavor and aroma comes from this koji fermentation process and koji penetrating the center of the bean is unique to O’Long.

Once the koji has gotten a chance to penetrate through the soybeans, they will be washed and cleaned, leaving the koji inside the soybean to continue to ferment. They’ll steam the soybeans again at 50C to break down the inside of the bean. 

The steamed soybeans are dumped into a barrel and will be mixed with a carefully selected ratio of salt and water. It will be dropped into large barrels made of fiberglass-reinforced plastic, then covered with a thick layer of salt to trap in moisture and air, and left covered in the barrel and untouched inside their temperature-controlled greenhouse to ferment for 120+ days. 

Once the soybeans are fermented, they go off to a presser. In many layers over 2 stories high, the soybeans will be pressed and its liquid collected: This is the first form of soy sauce. 

The collected sauce is pumped into vats where it’s cooked for 2-3 hours. In contrast to Japanese soy sauces, there is no wheat to influence aroma and flavor. After this first cook, the raw soy sauce is cooked again in batches, with various ratios mixed with additional salt and sugar to adjust for flavor and aroma. (For thicker soy sauces, whole glutinous rice is ground into a paste and added as a thickener.)

► Why do Taiwanese soy sauces add sugar? Tainan’s flavor profile is sweet, across its street food, high-end food, sauces, etc. and the traditional way to make a Taiwanese soy sauce is to use sugar. Because of this, salt content is often lower and there are no preservatives like alcohol that are needed post-fermentation, as sugar is a natural preservative that stabilizes the sauce, preventing bacteria from growing. This is why you won’t see any alcohol or other preservatives in this sauce. 

After bottling in sanitized glass bottles, the soy sauce and its bottle is pasteurized once more to rid the sauce of any remaining bacteria. Then, it’s labeled and shipped off to its various endpoints: While Taiwan is the biggest consumer of its 2.1M bottles produced per year, they also sell to various parts of Asia, Australia, the United States, Canada, Brazil and soon, Austria.

► Why can’t soy sauce be pasteurized in plastic bottles? The pasteurization process after the sauce is bottled requires temperatures of 90℃+, which is too hot for plastic to safely survive. And, without a second pasteurization, preservatives like alcohol need to be added to ensure food safety. 

Large-Scale Production: Ta Tung 大同

Ta Tung was established in 1911 in Xiluo, which is by the river and known as the birthplace of modern Taiwanese soy sauce. (The stories vary; some will say it’s because the river near Xilou is good for black soybeans to grow in, others will say that it’s a convenient place to wash soybeans) 

Ta Tung sells to “whoever they can get,” and they got Din Tai Fung which is a claim to fame. We met with Jimmy Tseng, who is a long-time manager there. They’ve created an entire tourism machine where they will bus in, in their words, housewives who can buy the sauce. They do brief tours with a DIY soy sauce making demo. 

As we toured the factory, we observed a few things: 

• Not all Ta Tung are the same: They have varying degrees of quality without it being clear on the label. For example, their lower-end sauces are made with sugar from Guatemala and are less refined. Their higher-end sauces are made with sugar from Thailand which are more refined.

• They work with local soybean farms: While their sugars and rice flours are imported, they work with local soybean farms to ferment their sauces. It’s unclear what percent is local vs imported. 

• They use earthenware to ferment: It’s unclear if all their soybeans are fermented this way, but there was a large number of clay pots outside the factory where soybeans are fermenting. Given their volume, it’s possible not all their soybeans are fermented this way. 

Small-Batch Craft: Amber River

We met with Byron who is a second generation soy sauce maker who does the traditional, handmade method from end-to-end. 

He sources black soybeans locally, and is one of two producers who still use a live fire to boil the raw soybeans. After boiling and cultured with koji, they are left to ferment on their own for 5 days in bamboo baskets. Instead of using temperature control to know when the soybeans are finished fermenting, he does fermentation by “feeling” - walking by the soybeans to sense how they are doing, rotating or stopping when they “feel” right. This is in huge contrast to O’Long in which everything is extremely precisely measured and controlled through years and batches of experimentation. 

The fermented soybeans are moved to earthenware pots where they ferment with salt and water for a “wet fermentation” (to get sauce) or just salt for a “dry fermentation” (to get flavor). They’re left outside to ferment with the elements. But, because the climate in central Taiwan is generally consistent year-round, this often doesn’t prove to be an issue. 

After 450 days of fermenting, the sauce is extracted and heated over a wood fire, then blended with flavors from dry fermentation, sugar, and water to create their soy sauce. 

Final Thoughts: Why Taiwanese Soy Sauce Deserves the Spotlight 

What struck me most on this trip was how each soy sauce tells a story — about its region, its maker, and Taiwan’s complex food heritage. From the high-tech fermentation rooms of O’Long to Byron’s bamboo baskets and wood fires, every producer honors their own version of the same process.

And while Japanese soy sauce might dominate supermarket shelves, Taiwanese soy sauces offer incredible depth, natural sweetness, and tradition worth exploring.

Want to Taste the Difference for Yourself? 

If you’re curious about the flavors I experienced, or want to learn how to use these soy sauces in dumpling dipping sauces, braises, and more — check out my dumpling cooking classes in San Francisco. I always keep a bottle of real-deal Taiwanese soy sauce on the table.

👉 Join a class or grab a bottle here → eatingwithedmund.com/book

- Eddie Lo, July 2025