Shoyu Koji (Soy Sauce Koji) (醤油麹)
Koji matured in soy sauce instead of salt water - a dark, ready-to-use seasoning with the depth of shoyu and the sweetness of koji.
| What it is | Rice koji soaked and matured in soy sauce until the grains soften and the liquid thickens |
|---|---|
| Taste | Soy sauce deepened and rounded; less sharp than shoyu poured straight |
| Typical uses | Dressing for blanched greens, a topping for rice or tofu, a marinade base |
Shoyu koji is the second of the two everyday koji seasonings. Where shio koji seasons with salt, shoyu koji seasons with soy sauce that has been mellowed by the koji's enzymes, so a small amount carries both salt and savoury flavour.
It is sold ready-made in jars and is also the seasoned base for quick pickles and egg marinades in Japanese home cooking. Because it contains soy sauce, it normally contains wheat unless made with a tamari base - check the label if that matters to you.
Like shio koji, ready-made products are the dependable choice; storage follows the maker's label, usually refrigeration after opening.
See also
Shio kojiRelated page in this guide.What is shoyu?
Related page in this guide.
Sources: Ministry of Agriculture, Forestry and Fisheries (MAFF), 'Traditional Foods in Japan'; JAS soy sauce standards; Umami Information Center; Kikkoman official information; Wikipedia (CC BY-SA 4.0). Checked 6 November 2026.