Protease Activity

Protease activity quantifies koji's power to break down protein into amino acids. Higher activity means more efficient soybean protein breakdown and richer umami.

Measured using standard analytical methods with casein substrates. For bean miso where soybeans dominate, protease activity is the most critical flavor determinant. Managing koji-making temperature carefully around 33-36°C tends to generate more protease. Enzyme 'quality' determines miso 'quality.'

Measurement commonly uses colorimetric methods with casein or hemoglobin substrates. Koji mold secretes acid, neutral, and alkaline proteases, each playing different roles at various miso maturation stages. Understanding enzyme diversity enhances the ability to design flavor.