Kōji

Question 1

List the components that are produced by kōji mould

Answer 1

Sugar, amino acids, peptides, vitamins, lipids (including fatty acids), subtle chestnut aromas and flavins

Question 2

How is sugar created and why is it needed?

Answer 2

It is created by the action of amylase enzymes on starch. It is needed as a source of energy for the yeast. No sugar means no fermentation

Question 3

How are the amino acids and peptides produced and why are they needed?

Answer 3

They are produced by the action of protease on proteins They are an important yeast nutrient, and they contribute towards the umami in a sake

Question 4

Name the three main amylases that are produced by kōji mould

Answer 4

Alpha-amylase, glucoamylase and alpha-glucosidase

Question 5

What are the difference between yellow, black and white kōji mould?

Answer 5

Yellow kōji mould are most commonly used in sake production, while black and white kōji mould produce high levels of citric acid and are not widely used in sake production.

Question 6

Name the two styles of kōji?

Answer 6

Sō-haze and tsuki-haze

Question 7

Sō-haze kōji has high levels of…

Answer 7

Enzymes, vitamins, sugars, amino acids, fatty acid, and peptides

Question 8

Why is sō-haze kōji used for faster and warmer fermentations?

Answer 8

A faster, warmer fermentation means that the yeast are more active. they therefore need more nutrients to sustain this higher level of activity. Higher levels of enzymes that are widely distributed throughout the kōji and therefore more easily accessible, as well as the higher levels of yeast nutrients secreted by the kōji mould, provide the required levels of nutrients

Question 9

Is the mould growth evenly distributed throughout the rice grains classified as tsuki-haze?

Answer 9

No, the mould growth is patchy and there are whole sections of the grains where there is no mould growth

Question 10

For the production of tsuki-haze kōji, do you need high or low levels of proteases?

Answer 10

Low ( due to minimising the amount of time the rice is in the temperature range where the production is at its highest)

Question 11

For the production of tsuki-haze kōji, do you need high or low levels of amylases (especially glucoamylase)

Answer 11

High (special strains of kōji mould are used so that these levels can be achieved despite the low levels of overall mould growth)

Question 12

For tsuki-haze, why are low levels of proteases required?

Answer 12

Low levels of proteases mean that fewer amino acids and peptides are produced which results in low umami in the final sake. If the levels of proteases are too high then this will result in umami levels that are also too high.

Question 13

For tsuki-haze, why are high levels of amylases required?

Answer 13

The brewer has to limit the mould growth to limit the production of fatty acids. Therefore, in order to ensure the yeast have access to enough sugars that limited amount of mould that is present needs to produce high levels of amylases.

Question 14

What are the seven stages of Kōji production in order?

Answer 14

1. Bringing in
2. Spreading the spores and initial mould growth
3. Re-breaking up
4. Mounding
5. Middle work
6. Final work
7. Sending out and drying

Question 15

When does bringing in happen?

Answer 15

Hour 0

Question 16

What temperature is rice cooled to during bringing in?

Answer 16

32-35

Question 17

What happens to the rice once it has been cooled during the bringing in stage?

Answer 17

It is spread out on a large shallow bed in the kōji room