What makes soy sauce black?

Soy sauce is a dark, salty liquid sauce created by dissolving soybeans or digesting them with acid. Soy sauce produces both umami tastes and browning and liberates sugars in the process.

Soy sauce offers salt, sweetness, umami, and bitterness, and, to a lesser extent, a little bitter and umami taste. The flavor profile is well-balanced, making it a great condiment. Because of the salt, sweet, and umami flavors, you only notice the bitter aftertaste. During hydrolysis or fermentation, free amino acids have generated that combine to make natural monosodium glutamate, which is a critical component of the umami flavor.

But despite our fondness for soy sauce, we’re often baffled by its darkish appearance. In certain lighting conditions, it may seem black, while in other lighting conditions, it can appear to be an extremely dark red. Fortunately, a detailed explanation is provided that makes things much simpler to comprehend. We will attempt to keep things basic because there is chemistry involved.

Soy sauce is black or extremely dark brown owing to a chemical reaction known as the Maillard reaction. The exact process gives seared food its dark hue and crispness. The second reason soy sauce may appear black is due to the addition of food coloring or flavorings. Caramel may be added to sweeten and deepen a light soy sauce.

The Maillard reaction is a chemistry term that sounds exotic but is really quite common. The meat should be brown on one side and move freely when seared. Any culinary browning, including caramelizing sugar, is a Maillard process. This happens when amino acids interact with reducing sugars, such as table sugar or most natural sugars.

Historically, large urns were used to heat and ferment soybeans. Soybeans are now fermented in containers in heated chambers. The soybeans are accompanied by roasted grains, brine, and one of two molds: rice or soy. The combination of these ingredients over months at a heated temperature causes the sauce to brown and deepen.