Kōji Flashcards
List the components that are produced by kōji mould
Sugar, amino acids, peptides, vitamins, lipids (including fatty acids), subtle chestnut aromas and flavins
How is sugar created and why is it needed?
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
How are the amino acids and peptides produced and why are they needed?
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
Name the three main amylases that are produced by kōji mould
Alpha-amylase, glucoamylase and alpha-glucosidase
What are the difference between yellow, black and white kōji mould?
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.
Name the two styles of kōji?
Sō-haze and tsuki-haze
Sō-haze kōji has high levels of…
Enzymes, vitamins, sugars, amino acids, fatty acid, and peptides
Why is sō-haze kōji used for faster and warmer fermentations?
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
Is the mould growth evenly distributed throughout the rice grains classified as tsuki-haze?
No, the mould growth is patchy and there are whole sections of the grains where there is no mould growth
For the production of tsuki-haze kōji, do you need high or low levels of proteases?
Low ( due to minimising the amount of time the rice is in the temperature range where the production is at its highest)
For the production of tsuki-haze kōji, do you need high or low levels of amylases (especially glucoamylase)
High (special strains of kōji mould are used so that these levels can be achieved despite the low levels of overall mould growth)
For tsuki-haze, why are low levels of proteases required?
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.
For tsuki-haze, why are high levels of amylases required?
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.
What are the seven stages of Kōji production in order?
- Bringing in
- Spreading the spores and initial mould growth
- Re-breaking up
- Mounding
- Middle work
- Final work
- Sending out and drying
When does bringing in happen?
Hour 0
What temperature is rice cooled to during bringing in?
32-35
What happens to the rice once it has been cooled during the bringing in stage?
It is spread out on a large shallow bed in the kōji room
When does Speading the spores and initial mould growth happen?
Hours 1-3 until hours 10-12
What happens to the temperature during spreading the spores and initial mould growth?
It slowly rises back to around 33-35°C (92-95°F)
What is the aim of the stage of spreading the spores and initial mould growth?
To spread the correct amount of spores for the style of kōji being made and to encourage mould germination and growth
What happens to the rice grains once they have been inoculated?
They are formed into a large pile and wrapped in blankets to retain warmth and moisture
When does re-breaking up happen
Hours 10-12
What happens to the temperature during spreading re-breaking up?
The temperature of the rice has risen to about 33°C (92°F) and is reduced to about 31°C (88°F); it then rises back up after a few hours to about 33°C (92°F)
What is the aim of re-breaking up?
To ensure that the mould grows evenly throughout the mass of grains and to eliminate any hot spots