Whole soybeans are cooked in pressure-cookers and mixed with roasted coarsely broken wheat or rice. The mass is inoculated with a mould, Aspergillus oryzae (or A. sojae) and incubated in doughnut-shaped circular plates with perforated bottoms through which air is forced. After two days of incubation under controlled conditions of temperature and moisture, mould growth covers the entire mass, called ‘Koji’, which is mixed with chilled brine and transferred to deep fermentation tanks. Osmophilic yeast cultures are added and slurry (called ‘Moromi-mash’) is allowed to ferment at controlled temperature and occasional aeration for 4-8 months. In the refining stage, the fermented mash is pressed to separate the liquid from the solid residue. The liquid is filtered, clarified, and heated to 90-95 degree Celsius. to pasteurize and to develop the characteristic color and aroma. After final clarification the sauce is pasteurized again and bottled.