Why Is Soy Sauce Black? (The Science Behind It)

Soy sauce is primarily used to season food and add lots of flavors to a recipe. But more than just influencing taste, soy sauce also lends its dark color to dishes.

It comes in varying degrees of light and dark but you may particularly be wondering why soy sauce is black. I did the research and here is what I learned!

Why Is Soy Sauce Black?

Soy sauce turns black or dark brown because of the Maillard reaction, the process of browning food. Soy sauce’s Maillard reaction occurs when warm temperatures during the fermentation process slowly brown it. Moreover, some soy sauces have added ingredients like caramel and the natural sugars in grains and soy also make soy sauce darker.

Are you curious about how exactly soy sauce turns black, what different soy sauce colors are, and more? Keep on reading to find out!

How Does Soy Sauce Become Black?

Soy sauce becomes black due to a combination of factors which are:

1. Maillard Reaction

The Maillard reaction occurs because of a chemical reaction between reducing sugars and amino acids and heat, creating new colors, flavors, and aromas in foods like soy sauce.

Browning through cooking is part of the Maillard reaction because of heat and time along with the reaction of amino acids and reducing sugars, like when you would sear a steak.

So how does this reaction occur in soy sauce when soy sauce does not get cooked?

In ancient times, soy sauce was made by fermenting soybeans in big urns under the sun, heating the soybeans, and slowly giving them a darker color.

Modern soy sauce still ferments in warm temperatures, allowing the ingredients to slowly darken over time.

Additionally, soy sauce gets darker the longer it ferments because it is exposed to more heat, deepening the flavor and color of the sauce.

Moreover, the natural sugars in the grains and soy darken and reduce, slowly adding to the dark color of soy sauce.

2. Added Coloring

Certain ingredients like added colorings or sweeteners can make soy sauce black or very dark brown.

For instance, caramel is a sweetener that is often added to light soy sauce for flavor and to darken it.

Can Soy Sauce Come In Different Colors?

Why Is Soy Sauce Black?

Soy sauce can come in different colors because they go through different fermentation processes and have different ingredients.

While soy sauce is often very dark, it can come in an array of colors, typically ranging from brown to golden colors.

Does Soy Sauce Change Color?

Soy sauce can change color over time because of oxidation, meaning that soy sauce gets darker when you expose it to air.

Once you open a bottle of soy sauce, it will slowly get darker the longer it has been open.

What Color Is Light Soy Sauce?

Light soy sauce is a golden brown color because it is made from the first pressing of soybeans, meaning it will not be as dark as soy sauce that ferments longer.

What Color Is Dark Soy Sauce?

Dark soy sauce has a very deep and almost black color because it ferments for a long time.

Moreover, dark soy sauce can contain other ingredients like caramel to further deepen its color.

What Color Is Kikkoman Soy Sauce?

Kikkoman soy sauce has a uniquely clear and reddish-brown color thanks to the Maillard reaction.

What Color Is Double Black Soy Sauce?

Double black soy sauce is a very dark brown color that is nearly black, similar to dark soy sauce.

There are usually additional ingredients like sweeteners added to double black soy sauce to make it darker than dark soy sauce.

What Color Is Tamari Soy Sauce?

Tamari soy sauce is a dark brown color but it may look black in bottles. Despite being a very dark color, it is often considered a light soy sauce.

What Color Is Low Sodium Soy Sauce?

Low sodium soy sauce is normally a very dark brown color due to the fermentation process but the exact color will depend on the brand.

If you want to learn more about soy sauce, you can see our related posts on why soy sauce is so good, why soy sauce is so popular, and why soy sauce is so salty.


Soy sauce is black due to chemical reactions that occur during the fermentation process, along with other factors like added darkening sweeteners.

However, soy sauce can come in a variety of colors because they contain different ingredients and fermentation processes.

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