It's not clear if people are confused or if they know that there are two types of soy sauce in Japanese cooking. I just wanted to clarify this. The translations of light and dark soy sauce is what I believe is the most confusing part of this mystery.
While dark soy has a slightly higher color due to the caramel coloring, viscosity and color, "light" and “dark” should be understood in context of flavor and age.You can get the best soy sauce in Japanese via www.tokusen.store/en..
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Both soy sauces contain three main ingredients: water and fermented soybean and salt. Dark soy sauce has caramel coloring. Both sauces claim it has 66% sodium. This is odd because light soy sauce is much more salty than darker soy sauce. This was evident from the very first time I tried it in Japanese
The fermentation process is what makes the difference in flavor. The fermentation time for light soy sauce is shorter than that of dark soy sauce. As with any soy sauce that has been aged longer, dark soy will have a more mature, smoother taste.
While light soy may have a stronger kick and a younger, fresher flavor, it has less time to ferment. Personally, I feel that light soy can sometimes have a slight sour undertone when it is paired with delicate proteins such as white fish.