Description
Stone pressing creates anaerobic conditions for koji enzyme activity while preventing oxidative spoilage.
Technical
Granite weights (10-30kg) exert 0.2-0.5psi pressure on miso paste, collapsing air pockets while allowing CO2 diffusion through cloth. The technique combines physical exclusion of oxygen with biochemical control of Aspergillus oryzae metabolism.
Culinary Significance
Traditional stone pressing yields deeper umami complexity than vacuum-sealed fermentation, as gradual pressure changes promote layered enzymatic breakdown. Artisans adjust stone weight seasonally - lighter in winter for slower fermentation, heavier in summer to accelerate proteolysis.
Science
Primary Reaction
Lactic acid fermentation
Parameters
Temperature
20°C optimal
10°C to 30°C range
Temperature range for optimal koji activity and miso fermentation
Time
1 year
6 months – 2 years
White miso requires shorter duration than red varieties
Equipment