After successfully brewing a small batch of sake, I decided to try my hand at growing koji. There are a lot of good resources out there to get started, but I wanted to document my success/failure.

Spores for yellow koji are easy to find. White koji, on the other hand was harder to track down. This kind of koji produces citric acid in higher quantities and made for a dry bright sake. I eventually found spores through a shop on Etsy.

• Prepare rice:
  • Soaked 2lbs of sushi rice overnight
    • Some recommend long grain rice
  • Drain and rinse the next morning
  • Steam until gelatinized (firm, but edible)
    • Took about 45min
  • Cool to 100F
• Inoculate:
  • Koji spores were mixes 1:2 with rice flour (optional)
  • 2 tbsp were sprinkled through a strainer and mixed into koji
  • Rice was spread out on 2 glass dishes (about an inch thick)
    • Then covered with a folded paper towel and sprayed with water until damp
    • Foil was used to loosely cover the trays – several small holes poked
• Grow:
  • Trays placed in oven
    • Originally placed in top tray of oven with light on, but heated up to 104F
    • Moved to bottom rack… stilltoo warm
    • Oven cracked slightly with chop stick
  • 24 hours
    • Light spots on rice, but no fuzz
    • Mixed by hand and sprayed paper towel
  • 48 hours
    • Lots of white fuzz
    • Broke up the mat, mixed and sprayed
    • Temp was way up!
      • Foil removed
      • Covered with damp tea towel
      • Oven light turned off
  • 72 hours
    • The rice is now a solid, thick, white, fuzzy mat!
    • Packed into a ziplock bag and placed in the freezer
      • Sounds like this is the best way to store koji for up to a year.

Why grow your own?

Not only was I curious, but white koji can be expensive in large quantities. I will be needing a bunch to make some large batches of:

• Sake
• Miso
• Soy sauce, or this

Update:

Decided to use this koji on a 2nd batch of sake.

• Getting started
  • Soaked and steamed 10lbs of calrose rice
  • Build up a starter of fresh Sake #9 Yeast | Wyeast 4134
• 5/5
  • Added the following to a large carboy. This is by wet weight, and was about 1/3 of the total ingredients. This will allow me to add a 2nd, larger addition in a few days.
    • 1 part koji – 20oz
    • 4 parts rice – 80oz
    • 6 parts water – 120oz, about a gallon
    • Yeast nutrient
    • Yeast starter
  • Places is the cool basement at 65 to ferment slowly this time.
• 5/13
  • Added the rest of the rice, koji, a gallon of h20 + 1 extra qt of water to make up for the extra koji
  • Total “dry”: 10lb rice, 2lb rice koji, 9qt water.