Preparing Koji

Question 1

What’s the main purpose of koji?

Answer 1

To provide enzymes that break down rice starches to fermentable sugars

Question 2

Under Japanese law, what is the minimum % of rice used to make koji for premium sake?

Answer 2

15%

Question 3

Name 4 components of koji that affect the style & quality of a sake?

Answer 3

1. Amino acids & peptides are created when the protein in rice is broken down. They are important yeast nutrients & contribute to the umami and slight acidity.
2. Vitamins which are important yeast nutrients
3. Lipids & proteins
4. Other subtle aroma/flavour molecules, in particular chestnut aroma

Question 4

Name the 2 styles of koji

Answer 4

1. So-haze
2. Tsuki-haze

Question 5

Describe 5 characteristics of So-haze style koji

Answer 5

1. Koji mould covers entire grain, sending many feeding tubes into the centre if the rice.
2. Encouraged by using rice grains with higher moisture content
3. High level of enzymes, vitamins, sugars, amino acids & peptides are produced
4. Faster starch to sugar conversion & to support a faster & warmer fermentation
5. Gives more body & flavour to the final sake

Question 6

Describe the 5 characteristics of Tsuki-haze style koji

Answer 6

1. Koji mould grows in a lightly spotted pattern over the rice grain
2. Grains with lesser moisture is required to prevent mould over growth
3. Grains are slightly firmer to make it harder for mould to penetrate.
4. Limited enzymes produced leading to lightly textured & delicate ginjo style
5. Slow controlled cold fermentation for ginjo-ka

Question 7

Name the 7 steps of koji making

Answer 7

BSR-MM-FS

1. Bringing in (Hikikomi) Hour 0.
2. Spreading the spores (Tanekiri) & initial mould growth: Hour 1-3.
3. Re-breaking up (Kirikaeshi): Hours 10-12.
4. Mounding (Mori): Hours 20-23.
5. Middle work (Naka-shigoto): Hours 30-33.
6. Final work (Shimai-shigoto): Hours 36-38.
7. Sending out (De-koji): Hours 44-48.

Question 8

Name the 3 methods of managing level & distribution of mould growth in handmade koji

Answer 8

1. Bed koji (Toko-koji). 100-300kg. Big batch with little precision. Futsu-shu, Honjozo, Junmai & some Ginjo.
2. Box koji (Hako-koji). 15-40kg. Can be used for wide range of sake. Too labour intensive for Futsu-shu & not accurate enough for Daiginjo.
3. Tray koji (Futa-koji). 1.5-2.5kg. Most precise control of temperature & water content. Labour intensive & optimal for the best Daiginjo.

Question 9

What are the 3 types of koji?

Answer 9

1. Yellow (Aspergillus oryzae)
2. Black
3. White

Yellow koji is the most common used for sake brewing. It produces lower levels of citric acid.

Question 10

Name the 2 formats of koji mould

Answer 10

1. Powdered: Mould spores. Able to inoculate continuously at a constant density. Suitable for So-haze.
2. Granulated: Rice grains that have already been inoculated with mould. Fewer spores hence able to achieve a light & even covering of spores. Suitable for Tsuki-haze

Question 11

Name 2 types of sake suitable for So-haze

Answer 11

1. Futsu-Shu. Boost flavour & compensate for dilution when Jozo alcohol is added
2. Premium sake with intense flavours, full body, high acidity & umami

Question 12

Name 2 types of sake suitable for Tsuki-haze

Answer 12

1. Ginjo/Daiginjo. Delicate & pure flavours with Ginjo-ka. Low acidity & umami.
2. Honjozo. With lean texture & restrained aromas

Question 13

Name 2 conditions for koji mould to grow & thrive

Answer 13

1. Warm temperature
2. High Level of water in rice grain

Question 14

How long does it take to make Koji?

Answer 14

About 44-48 hours

Question 15

Name the 3 steps of how koji mould grows.

Answer 15

1. Sending feeding tubes (hyphae) into rice grain.
2. These tubes secrete enzymes that break down starch into glucose.
3. Glucose is absorbed thru the hyphae to support further growth.