Japanese Soy Sauce Production — Regional Styles and Varieties
Japan-wide — production concentrated in Chiba, Hyogo, Aichi prefectures
Japanese soy sauce (shoyu) is a fermented condiment of profound complexity produced from wheat and soybeans (standard koikuchi), soybeans and wheat at higher wheat ratio (tamari, which is thicker), or special regional variations. The primary varieties: Koikuchi (dark, standard, 80% of Japanese production — from Chiba and Hyogo prefectures); Usukuchi (light-coloured but saltier, from Hyogo's Tatsuno — used in Kansai cooking); Tamari (thick, wheat-free or low-wheat, from Aichi and Mie — used for dipping and finishing); Shiro shoyu (white, almost colourless, from Aichi — maximum wheat, minimum colour); Saishikomi (double-brewed, very dark and rich — from Yamaguchi). Production: soybeans are boiled, mixed with toasted wheat, inoculated with Aspergillus sojae or A. oryzae to make koji, combined with brine to make moromi mash, fermented in cedar barrels 6–36 months, pressed, and pasteurised. Barrel-aged shoyu (kioke jukusei) from traditional producers is increasingly rare and precious.