Rice (Oryza sativa)
Rice
Japanese: 米（こめ）
The most common grain used as a substrate for koji. Rich in starch for saccharification.
In Japanese fermentation, rice is the most fundamental grain serving as home for koji mold. Koji takes root on steamed rice, converting starch into sugars.
Starch composition differs between regular and glutinous rice, producing different flavors. Regular rice is common for miso, glutinous rice sometimes chosen for amazake. Hardness and water absorption vary by cultivar. Adjusting milling rate changes koji character. Brown rice koji yields robust flavor; highly polished rice produces elegant sweetness. Ingredient choice defines fermentation personality.