7 Steps of Koji Making

Question 1

Bringing In (Hikkomi)

Name the time & aim.

Answer 1

• Hour 0
• Aim: Transferred to koji room once it has reached the right temperature
• Rice from the steamer is reduced to 32-35°C

Handmade koji cooled on mats.

Machine-made koji done on a conveyor linked to a continuous steamer.

Question 2

Spreading the spores (Tanekiri) & Initial mould growth

Name the time & aim.

Answer 2

• Hour 1-3. Takes about 10-12 hours.
• Aim: Inoculation & encourage mould growth. Ensure spores are spread evenly.
• Starts at 30-32°C and rises to 33-35°C.

Handmade koji done on koji table with shakers. Covered with blankets to retain warmth & moisture.

Machine-made koji inoculated by spraying during transfer by pipe to koji making machine. Temperature & humidity is machine controlled.

Question 3

Re-breaking Up (Kiraikaeshi)

Name the time & aim.

Answer 3

• Hours 10-12.
• Aim: Ensure even mould growth & avoid hot spots.
• Temperature rises to 33°C and reduced to 31°C

Handmade koji is spread out on bed & broken up by hand. Wrapped up again for another 8-12 hours.

Machine-made koji broken up by rotating rollers. Temperature & humidity are machine controlled.

Question 4

Mounding (Mori)

Name the time & aim.

Answer 4

• Hours 20-23
• Aim: Manage level & distribution of mould growth.
• Temperature rises to 33°C & continues rising to 35°C

Mid point of koji making.

Handmade koji, brewer has to decide what methods to use for the desired koji style. Most labour intensive part. Unwrapped & spread out. Moved to a less humid part of room. Another 7-10 hours.

Machine-made koji remains in drums. Temperature & humidity are machine controlled.

Question 5

Middle Work (Naka-shigoto)

Name the time & aim.

Answer 5

• Hours 30-33.
• Aim: Encourage release of heat & to start drying out the grains.
• Temperature reduced from 36°C to 33°C and rises again to 38°C.

Handmade koji has to be spread out to release heat & start drying out. Important as koji growth is most vigorous at this stage. Overheating will kill koji providing undesirable flavours.

Machine-made koji, rotating rollers redistribute the rice & draw patterns to allow heat & water to escape.

Question 6

Final Work (Shimai-shigoto)

Name the time & aim.

Answer 6

• Hours 36-38.
• Aim: Continue drying out the grains & continue release heat by koji activity. Make surface drier than center.
• Temperature about 38°C but not higher than 43°C so as not to stress the mould.

Handmade koji to continue spreading out koji. Mould is encouraged to seek moisture at the centre.

Machine-made koji, rotating rollers continues reshaping the surface. Temperature & humidity are machine controlled.

Question 7

Sending Out (De-koji)

Name the time & aim.

Answer 7

• Hours 44-48.
• Aim: Stop mould growth by cooling down & drying out the grains.
• Temperature is reduced from 38°C to brewery ambient temperature.

Handmade koji are transferred to separate part of koji room with ambient temperature.

Machine-made koji, temperature is automatically reduced.