Koji-buai (Koji ratio)
Koji-buai
Japanese: 麹歩合（こうじぶあい）
The ratio of koji to soybeans. The most critical parameter determining miso sweetness or saltiness.
Koji buai expresses how much koji is used relative to soybean weight. 5-6 wari yields salty red miso; 10-12 standard rice miso; 20-30 sweet white miso.
More koji means more saccharification and sweetness, but higher cost. Less yields saltier, protein-focused miso. This single number determines flavor structure, making it the starting point of recipe design. To find your preferred balance, start with standard 10 wari, then compare with 8 or 15. Changing koji ratio alone creates remarkably different miso. Experimenting with ratios teaches the depth of miso making.