C9 - Preparing Koji - working Flashcards
what happen to the koji mould if the temperature is cold and dry?
it will stop growing
how tsuki-haze influence the style of the sake?
- it’s ideal for the slow, controlled, cold fermentation for making ginjo style
- low level of lipid restricted the fungal growth
- low level of vitamins and proteins give a more light texture and delicate style of ginjo aromas
- it’s low acidity and low in umami
why barley can breakdown the starch without the aid of koji?
because malted barley (or rice with germ) can use germination to activate the grain’s own starch-to-sugar enzymes.
How koji-making machine do the “re-breaking up” process?
- it uses the rotating roller to breakup the rice
- temperature and humidity a automatically preset
how so-haze koji perform during fermentation?
- it is fast in starch to sugar conversion
- usually use in a warmer and faster fermentation
- it adds intense flavours, full body, high acidity and high umami to the sake produce.
What does middle work do (naka-shigoto)?
- flattening the shape of the mound
- drawing patterns on the surface
- in order to increase the surface area of the mound
- which help dispersing heat and evaporate water
why tsuki-haze is difficult to make?
it needs a great deal of skill to create
what are the main acid types of sake?
- succinic acid
- malic acid
- lactic acid
what is box koji (hako-koji)
- ~15 - 40kg medium size box
- often with an divider for separating the rice to half in the box
- labour intensive
- suitable for style in between futsu-shu and daiginjo
how the koji mould breakdown the starch in a rice grain?
- the koji mould sending it’s feeding tube (hyphae) into the rice grain
- the feeding tube has enzymes hided by other components
- the enzyme then breakdown the starch into glucose
- the glucose are absorbed by the feeding tube
what is the ideal condition of the rice grain for growing tsuki-haze koji?
- less moist, so the mould is harder to grow on the surface
- a firmer exterior, so the mould’s feeding tube is difficult to penetrate
what is “Bringing in (hikikomi)?
- hour 0: it’s the starting point of making koji
- steamed rice are cooled down to 32-35C
- then the cooled rice is transferred to the koji room
why it needs a special koji room to grow the koji mould?
the koji-room (koji-muro) is temperature and humidity controlled.
how the koji-making machine do the middle work?
- use rotating rollers to redistribute the rice and draw patterns
What is the aim of middle work (naka-shigoto)?
- reduce the rice temperature from 36C to 33C, then rise to 38C
- disperse heat
- drying the rice
Why do you not stop the mould growth by heating it?
Because heating will cause off-flavours and de-activate enzymes and vitamins created by the mould.
How many varieties of koji mould?
3:
- yellow
- black
- white
how machines spread the spores and let it grow?
- spores are sprayed to the rice when transferring from the steamer to the koji-making machine
- rice are laid out in a large drum with temperature and humidity control
- a rotating roller moves the rice
- the machines creates a warm and humid environment to encourage mould growth
what is koji?
Koji is a culture of filamentous fungi grown on cereal grains.
When does the Middle Work (naka-shigoto) start?
- hour: 30 - 33
describe the characteristics of so-haze koji:
- the koji mould covers the entire rice grain surface
- sending many feeding tubes deep into the rice core
- it has high levels of enzymes, amino acid, vitamin, sugar and peptide.
What is the percentage of koji in most of the sake today?
around 20%
What is bed koji (toko-koji)?
- rice is kept complete the koji-making process on the bed (toko)
- the koji batch volume is around 100-300kg
- not possible for the highest precision control
- suitable for futsu-shu, junmai, honjozo.
- possibly for some ginjo but not daiginjo
what is the alternative of making koji the traditional way today?
using half or fully automated koji-making machines
what is the aim of “Final work”?
- focus shifted from dispersing heat to reduce the moisture
- drying out the grain’s outside, encourage the koji mould to grow to the core of the grain
- temperature of the rice is remain 38C, need to beware not to exceed 43C, otherwise the koji mould will under stress
why yellow koji is the mostly used in making sake?
because it has the lowest level of citric acid.
Acidity has been regarded as undesirable by sake drinkers for a long time.
how are the colours of the koji varieties come from?
the appearance of the koji inoculated rice grains
what was the limit of the koji-making machines in the beginning
it can only produce large scale but low quality koji
How’s the texture and aromas of Honjozo made with tsuki-haze?
it has a lean texture, and restrained aromas
what are the 3 options the brewer can choose to manage the moisture and temperature during Mounding (Mori)
using 3 different size of container for the koji:
- bed koji (toko-koji)
- box koji (hako-koji)
- tray koji (futa-koji)
How’s the koji mould growth activity after mounding, means during middle work?
at its most vigorous
what are the difference of cooling the rice in traditional way vs by machine in the brining-in stage?
- traditionally the steamed rice are spread on mat right outside the koji room
- machine uses cooling conveyor to cool down the rice and send to the koji-making machine directly
what is “sending out (de-koji)”?
- chilling the rice to ambient temperature to stop the mould growth
what is the main purpose of koji
to provide enzymes that break down the starches into fermentable sugars.
how the brewer spread the spores when making hand-made koji?
- the rice are spread on a large bed-like table (toko)
- koji spores are applied using hand shakers
- koji spores are spread in appropriate amount and evenly
What is the risk of mounding if the temperature is keeping too high?
it will kill the mould
what is the ideal environment for koji mould to grow?
- warm temperature
- high level of water in the rice grain
traditionally which material is used to cover the koji room?
Japanese cypress wood (hinoki)
what are the 7 stages of making koji after the rice is steamed?
- Bringing in (hikikomi)
- Spreading the spores (tanekiri) and initial mould growth
- re-breaking up (kirikaeshi)
- mounding (mori)
- bed koji (toko-koji)
- box koji (hako-koji)
- tray koji (futa-koji)
- middle work (naka-shigoto)
- final work (shimai-shigoto)
- sending out (de-koji)
what does Mounding (Mori) need to do?
- hour: 20 - 23
- temperature of the rice raise from 33C to 35C
- rice is unwrapped, spread out
- then move to a less humid part of the koji room
- the aim is to manage the level and distribution (pattern) of the mould growth
what are the two extreme styles of koji? what they call?
so-haze
tsuki-haze
When to start the “sending out” (de-koji)?
hour 44 - 48
what is the Japanese of “koji room”?
koji-muro
what is needs to create the tsuki-haze koji?
- the moisture level of the grain is controlled to low level
- the amount of koji mould spores are limited
- the koji room is relatively warmer and drier
What is Mounding (Mori)?
to manage the koji mould growth pattern to achieve the desired koji style e.g. tsuki-haze or so-haze
where the brewers get the koji mould from?
purchased from a small number of suppliers
What happened in case the koji mould died during mounding?
died koji creates undesirable aromas and flavours like sweat, which taints the sake.
why making koji the traditional way is very labour intensive?
- temperature and humidity need to be checked every 2 hours
- the rice needed to be worked by hand
what other components are provided by the koji mould while penetrating the rice grain?
- amino acid
- peptilde
- vitamin
- lipid and protein
- other subtle aroma and flavour molecules
describe what does “Re-breaking up (kirikaeshi)” do:
- hour 10 - 12:
- the temperature of the rice mound is raised to 33C
- the mound is broken up by hand, to help the mould grow evenly and dropping the temperature to 31C
- brewers work on the rice carefully and thoroughly to check and remediate any clumps and hot spots
- the rice than wrapped up again, temperature is raised back to 33C, humidity is also raised.
- the mould will keep growing for another 8-12 hours
Which tools the brewers use to draw pattern on the mounds of bed, tray and box koji during middle work?
- by hands: for the box and tray koji
- by using a “wooden plough” for the bed koji
what is tray koji (futa-koji)?
- ~1.5 - 2.5kg small size box
- this allow the most precise control of temperature and water content in the rice
- very labour intensive
- for the best daiginjo sakes
how is the temperature differ at the top and bottom of the containers with the koji rice?
- it’s warmer at the top
- cooler at the bottom
how the brewers adjust the mould growth rate in the containers to the same level?
- they check and re-arrange the containers in every few hours
How the rice are cooled down during “sending out” (de-koji) in the hand-making way?
- the vessels (tray, box, bed) are transferred to a separate part of the koji room, that’s at a cool ambient temperature.
- often use fans to blow cool air from below to speed up the cooling.
What does the brewer need to pay attention to during mounding (Mori)?
- the distribution of moisture and temperature of individual rice grain rather than the mass.
what is the objective of some brewers trying to use black or white koji?
- with the higher level of citric acid, to achieve a structure and balance similar to wine
where are the main acids in the sake come from?
the fermentation starter and the yeast
Will chilling the rice kill the koji mould?
no, it just de-activate it.
What do “spreading the spores (tanekiri) and initial mould growth” do?
- hour: 1-3 - after ‘bringing-in’, the initial mould growth till hour: 10-12 (~9 hours)
- temperature of the rice rise from 20-32C till 33-35C
- the aim is to inoculate koji spores to the rice grain and encourage mould growth.
what is the effect of tsuki-haze during fermentation?
- it has limited amount of enzymes
- the enzymes are released slowly
- the rice are broken up slowly
what is ‘nuri-haze’?
uneven koji mould growth due to the moisture level of the rice grain is too high.
what are the forms (formats) of the koji mould purchased?
- powdered
- granulated
why futsu-shu and premium sake both can use the so-haze koji?
futsu-shu:
- it boosts the flavour intensity
- compensate for the dilution caused by adding jozo alcohol
Premium sake:
- it adds intense flavour, full body, high umami and high acidity to the final sake
how the other components provided by koji mould affect the style and quality of the sake?
- amino acid and peptide are yeast nutrients and give umami flavour. slightly in acidity.
- vitamin are also yeast nutrients
- subtle aromas and flavours e.g. chestnut
In using koji-making machine, how the level and pattern of mould growth are determined?
- by adjusting the temperature, humidity or the machine
- using rollers to move the rice around
what’s the difference in the powdered koji mould and granulated koji mould
- powdered are koji mould spores
- granulated are rice with koji mould spores growing on it
How koji-making machine do the “final work”?
- keep using the rotating roller to reshape the rice, increase the surface area, encourage evaporation
describe the initial koji mould growth when making hand-make koji
- after inoculation, the rice are formed into a mound on the bed and covered by blanket to keep it warm and humid
- koji mould spores start germinating and grow
- the mould will generate heat when grow, temperature is being monitored and adjust if needed.
- the mound of rice will be left like this for 8-12 hours
what’s the other name of koji mould?
Asperguilus oryzae
how half-mechanised handling the koji rice containers work?
- the re-arrangement is moved by machine rather by hand
describe the appearance of tsuki-haze?
- the koji mould grows in a tiny spot pattern over the rice grain
- inside the rice grain, only part of the center has the feeding tube penetrated
Which material is now widely used to cover a modern koji room?
stainless steel
after the rice are transferred (or not) to the containers, how long the mould continue to grow?
another 7 - 10 hours
How to classify koji styles?
according to the level and pattern of the koji mould growth
which koji variety is the mostly used?
yellow koji
what are the changes happening in the koji-making machines today?
- more artisan brewers are willing to adapt the machines
- the quality keeps improving by collecting and compiling database
can sake be made entirely using koji?
yes, but just a few
why brewers making ginjo sake prefer to use granulated koji?
- it has fewer spores
- the spores can cover the rice surface lightly and evenly
- that’s required for making the tsuki-haze koji
By law, what’s the minimum percentage of koji need to use in fermentation?
15%
why most brewers use the powdered koji mould?
- since it has no rice grain
- it is suitable to inoculate continuously with a constant density
when to start the Final Work (shimai-shigoto)?
hour: 36 - 38
What is the disadvantage of using koji-making machine?
it’s not possible to have very precise control like hand made.
How the rice are cooled down during “sending out” (de-koji) using koji-making machine?
the temperature inside the drum is automatically reduced.
What are the 3 enzymes koji produces?
Alpha amylase
glucoamylase
glucosidase
