Koji

It names grain cultivated with a useful mold for fermentation.

The mold's enzymes break starch into sugars and proteins into amino acids, helping brewers and cooks make alcoholic drinks, pastes, sauces, and vinegars.

The practice has a long history in China and Japan. Chinese records reach before the Common Era; by the sixth century, Chinese accounts distinguish formed starter cakes for alcohol from loose-grain starter for seasonings. Japan's earliest cited record of loose rice koji is from the eighth century.

Why do 麹 and 麴 both appear?

麴 is traditional; 麹 is the customary simplified form in Japanese.

糀 is a character created in Japan for rice koji. In Japanese, 麹 writes the food term こうじ, commonly romanized kōji. Mandarin uses 麴 or 曲 for a related starter term, read qū—roughly “chü” with a high, level tone. These forms are historically connected, but their spellings and readings follow different conventions.

How do I type 麹?

Enter こうじ in a Japanese IME, then choose 麹.

If the candidates show 麴 or 糀 first, check which character fits the text: these are related forms, not display failures. Mandarin pinyin qū may suggest 曲 or 麴, so select the form required by the surrounding language.