【Reading】こいくちしょうゆ

【English Name】Dark Soy Sauce

The type of soy sauce with the top domestic consumption is koikuchi soy sauce (dark soy sauce). Made mainly from soybeans, wheat, and salt, its umami is concentrated through a three-stage fermentation by koji mold, lactic acid bacteria, and yeast. The Maillard reaction that occurs during heating brings about its distinctive reddish-brown color and complex aroma, and it projects a powerful individuality in both color and aroma compared with light soy sauce (usukuchi).

Until around the 1640s in the Edo period, Edo's soy sauce relied on shipping transport from the Kamigata region. As the rapid swelling of the urban population pushed up logistics costs, demand shifted toward the inexpensive Kanto-produced "jimawari soy sauce." With three conditions overlapping—salt from Gyotoku, the granary of the Kanto Plain, and a water-transport network—Noda and Choshi in Shimosa rose as major soy-sauce production areas. Their brewing culture has continued without interruption to the present day.

In the world of Edo-style sushi, it is an indispensable material as the base of dipping soy sauce and nikiri soy sauce, and its compatibility with shari and toppings is unrivaled by other seasonings. It also possesses an all-around versatility that supports Japanese cuisine as a whole, such as simmered dishes, soup bowls, and tempura dipping broth.

The main production areas today are centered on Chiba Prefecture and Hyogo Prefecture. Nutritionally, per 100 g it reaches about 53 kcal of energy, about 8 g of protein, and about 5,500 mg of sodium, so for everyday use it is advisable to moderate the amount.