Koikuchi Shoyu vs. Usukuchi Shoyu: Japanese Soy Sauce

Respectively known as “dark soy sauce” and “light soy sauce” in English-speaking countries,

Koikuchi Shoyu (濃口醤油) and Usukuchi Shoyu (薄口醤油) are the most common and basic types of soy sauce available in any supermarket in Japan.

Koikuchi Shoyu (Dark) vs. Usukuchi Shoyu (Light) Say Sauce

But do you know how Koikuchi Shoyu or dark soy sauce differs from Usukuchi Shoyu or light soy sauce?

This article will explain the difference for people who don’t know much.

Salt Concentration

You might think Usukuchi Shoyu has a lower salt concentration than Koikuchi Shoyu, as the former has a lighter color than the latter.

But the truth is the other way around.

Usukuchi Shoyu

While the salt concentration of Japanese dark soy sauce is generally 16 to 17 percent, that of Japanese light soy sauce is 18 to 19 percent.

The “light” in light soy sauce comes from its color, not taste.

In the production process, Usukuchi Shoyu uses more salt and has a shorter fermentation time, making its color lighter than Koikuchi Shoyu. 

Taste

Koikuchi Shoyu

As Koikuchi Shoyu/dark soy sauce has a longer fermentation process, it is more aromatic than Usukuchi Shoyu/light soy sauce, packed with flavor. 

Koikuchi Shoyu is the most basic soy sauce, and if the recipe calls for Shoyu, we usually use this soy sauce.

Usage

Most widely used in Japanese cuisine, Koikuchi Shoyu gives more “soy sauce” taste and aroma to the dish.

Meanwhile, commonly used in the local cuisine of Kyoto, Kyo-Ryori (京料理), Usukuchi Shoyu can accentuate the original taste and color of food materials.

(Reference Pages: Kawanaka Shoyu, Meiman, Ajinomoto )