Nebari koji (sticky koji)

Nebari koji (粘り麹, "sticky koji") refers to koji whose surface has been overgrown by a particular microorganism, Bacillus subtilis (known in Japanese as kusa-kin, 枯草菌), leaving it smooth and sticky. Koji in this state may form a dumpling-like lump when squeezed in the hand. It is generally regarded as a sign of poor growth of the koji mold, which prevents fermentation from proceeding properly and is likely to harm the quality of the sake. Because the condition of the koji is important in brewing good sake, nebari koji is often considered undesirable. For this reason it is also called "nururi koji" (ヌルリ麹, "slimy koji") and is treated as a type of koji that requires caution.