C2 - An Overview of Sake Production - completed Flashcards
What is the main raw material for making sake?
Steamed white rice
What is the function of water and kōji in making sake?
Rice is a solid with a starchy core that needs water and kōji to convert the solid starch into a sugary fermentable liquid.
What else is need to convert the sugars into alcohol?
yeast
Briefly describe the growing cycle of rice by season
- planted in spring
- grown in summer
- harvest in autumn
Rice is an ___ ___ crop
edible cereal
How long can rice be stored once it’s harvested?
a few months
What kind of land can the rice farmed?
- flooded rice-paddies in Japan
- dry fields, usually in the USA.
What are the two main subspecies of Asia rice?
1 - long grained (Indica)
2 - short grained (Japonica)
What are the two types of rice subdivided under Indica and Japonica?
1 - sticky (glutinous)
2 - non-sticky (non-glutinous)
Which type/spice of rice is only be used for brewing sake?
the non-sticky short grained rice.
List a few of the characteristics of the non-sticky short grained rice
- easy to farm
- high yield
- grown in Japan and elsewhere
- as table rice for eating
- also suitable for making sake
What are the challenges of growing sake-specific rice?
harder to farm and lower yields
Why the sake brewers like to use the sake-specific rice?
it’s easier to separate cleanly the starch from the proteins and other undesirable parts of the rice grain
Which 3 reasons make the sake-specific rice easier to separate the starch from the proteins of the rice grains?
- they contain less protein then table rice
- most of the starch granules lie in a well-defined almost pure starch core
- they are larger-grained, therefore less likely to crack when polished.
What is the first step to process the rice before being used in sake production?
polishing
What is the purpose of polishing the rice?
to remove the:
- proteins
- lipids
- vitamins and
- minerals
in the outter part of the rice grain.
Leaving just the starchy core
What is the polishing ratio referred to?
The amount of the remaining rice after polishing.
What is the difference between table rice and sake-specific rice in terms of polishing
table rice are less highly polished than rice used in sake brewing
Why the polishing ratio will affect the final style and category of the sake?
Polishing determined the amount of the rice is polished and the amount of proteins, lipids, viatmins and minerals that remain.
What is the second step after polishing?
- the rice grains need to be cleaned to remove any remaining fine rice powder
What is the purpose of cleaning and removing the fine rice powder?
- the powder is made up of tiny fragments of the bits of rice was trying to remove, they would make the sake less pure, more rough-textured and acidic.
How the fine rice powder is removed in the cleaning process?
by washing, either in:
- small container
- large vats
- or a continuous rice polishing machine
Characteristics of sake made from highly polished rice:
- have purer, fruitier flavours
- lighter in body
- lower acidity and umami
Characteristics of sake made from less highly polished (coarsely polished) rice:
- have more savory
- less fruity flavours
- more body
- more acidity
- more umami
- price tend to be lower
What are the 3rd and 4th steps after polishing?
- soaking and steaming rice
What is the purpose of soaking?
to alter the amount and distribution of water within the rice grain
What is the duration of soaking for the purest and most delicate sakes?
- a few minutes to be done precisely.
Traditionally, how many rice are steamed in batches
approximately one tonne, last about an hour
What are the 3 purposes of combining the soaking and steaming process?
1 - raising the moisture level within the grain
2 - changing the starch
3 - disinfection of the rice
Describe how soaking and steaming raise the moisture level within the grain
- soaking helps the rice absorbs enough water to be soft and moist inside.
- steaming (rather than boiling) means the outside of the rice remains firm.
What are the benefits of raising the moisture level with the grain?
- perfect the distribution of moisture for producing the best kōji
- make sure the rice breaks up during fermentation at the right speed
Describe how soaking and steaming change the starch
- The heat changes the structure of the starch, so that the kōji enzymes can break into fermentable sugars
- Without heat, the starch remains in a form that the kōji enzymes cannot break it apart.
What is the benefit of using steaming to disinfect the rice?
- steaming kills the undesirable microbes that may be on the rice which may contaminate the fermentation.
What is the next step after soaking and steaming?
making kōji
What is starch made up of?
starch is a large molecule made up of lots of sugar molecules all linked together.
Briefly, what is kōji?
- a mould which creates starch-converting enzymes. The mould is called kōji mould.
- The mouldy rice is called kōji
Why kōji is needed in making sake?
- kōji contain the chemical (enzyme) which can break up the starch into sugars, then the yeast can convert sugars to alcohol during fermentation.
Where can we find the enzymes to convert starch to sugar?
- in the natural world
- any living thing that can digest starch has these enzymes
- the outer part of cereal grains (rice, malt) also have these enzymes
Briefly, what is enzyme?
An enzyme is a kind of protein that trigger the chemical reactions to convert starch into sugar
do we need a large amount of enzyme to convert large amount of starch into sugar?
No, only a small amount of the right enzyme are needed to trigger the chemical reactions, since it won’t be used up during the chemical reaction.
Why beer can convert starch into sugar without kōji?
beer uses unpolished grains that can be malted to release the enzymes in the grains.
What is the ratio of kōji to rice used in sake brewing?
fifth to a quarter (1/4 to 1/5)
What is the ideal condition for kōji mould to grow?
- high humidity
- warm - temperature between 33C - 38C
When does the production of kōji start?
After the rice is taken out of the steamer
What are the four steps for making kōji?
1 - cooling
2 - inoculation
3 - initial mould growth
4 - controlling and stopping the mould growth
Describe what cooling does:
The steamed rice that will become kōji is cooled down to the right temperature.
Describe the inoculation process:
- the cooled steamed rice is transferred to the kōji room, spread out thinly over a table.
- kōji mould spores are sprinkled on the rice.
Describe the initial mould growth process:
- the warm and humid conditions in the kōji room encourage the spores to grow into mould
- the mould spreads and grows over all of the grains
- the rice is thoroughly mixed to ensure the growth of mould is even.
Describe “controlling and stopping the mould growth”:
- the rice with mould is transferred to racks in a cooler, less humid location in the kōji room
- the aim is to control the condition in order to slow down the mould growth to achieve the exact amount of mould grown on each grain
- Utlimately, the mould growth is stopped when the rice is moved to the coolest and driest part of the kōji room.
How long does the kōji production take?
about two days
Describe the appearance and taste of the finished kōji:
- it looks like policed rice with a crumbly texture
- it has slightly sweet chestnut flavour
Why precise control of kōji mould growth is important?
Because the brewer needs to use kōji with different amounts of mould to make different styles of sake.
What are the 2 major styles of kōji?
1 - kōji with high levels of kōji mould
2 - kōji with low levels of kōji mould
Why and how high levels of kōji mould affect the style of the final sake?
- the kōji mould covering the entire grain
- large amount of kōji mould means large amount of enzymes
- it can convert starch to sugar faster
- thus fermentation is faster
- the resulted sake tends to have more flavour intensity, more acidity and umami.
Why and how low levels of kōji mould affect the style of the final sake?
- only tiny amount of kōji mould dotting the outside of the grain
- only small amount of enzymes are created
- converting starch to sugar is slower
- fermentation is slower (take longer time)
- the resulted sake tends to be lighter in flavour, less acidity and umami
What level of control is needed to make kōji with low levels of kōji mould?
extreme precision control during all these aspects:
- rice polishing
- washing
- soaking and steaming
- the kōji room
typically which style of sake requires the use of kōji with low levels of kōji mould?
the purest, most delicate styles of ginjō
what is the proportion of water in a finished sake?
80%
what kind of water is preferred for sake making?
- clean
- low iron concentration
how the content of water affect the sake?
- mineral concentration of water affects the fermentation, thus the style of the sake.
What are the particular conditions in fermentation for sake yeast?
- yeast must keep working in high alcohol level over 20% abv
- yeast needs to work in low temperature, e.g. the fermentation temperature for ginjō can be as low as 6C
- ginjō fermentation have very low levels of sugar, means very limited food supply for the yeast
What is the solution to deal with these particular condition in fermentation?
certain particular yeast strains that can tolerate these situation have been identified, isolated and shared between brewers
What is the other reason those particular yeast strains are chosen besides they can tolerate the harsh fermentation conditions?
They have particular desirable properties i.e. being very reliable or can produce interesting aromas.
What is the contribution of yeast to the sake style? and why?
- yeast contribute greatly to the aroma in most sakes
- because the absence of distinct aromas and flavours from the rice, or the kōji or water.
What are the 5 steps of preparing the rice for fermentation?
1 - polishing
2 - washing
3 & 4 - soaking and steaming
5 - making kōji
What are the 4 ingredients for sake fermentation?
1 - steamed rice
2 - kōji
3 - water
4 - yeast
What are the 4 key steps of making sake?
1 - the fermentation starter
2 - the main fermentation
3 - jōzō alcohol and filtration
4 - finishing
Why there’s a risk of contamination during sake fermentation
While the kōji enzymes are turning rice starch into sugar, the healthy yeast needs time to build up its population, other undesirable microbes (yeast, mould, bacteria) could settle in the liquid, consume the sugars and spoil the flavour of the sake.
How brewer avoid the contamination to all the sake before the main fermentation?
The brewer takes a small portion of the ingredients (kōji, rice, water, yeast) and make a mini fermentation, usually in a separate small tank. This is the fermentation starter.
What is commonly added to the fermentation starter to prevent contamination? Why?
- increase the acidity of the water by adding lactic acid.
- because the sake yeast is bred to tolerate this acid better than any of the spoilage microbes.
The fermentation starter is left until what situation is achieved?
Until the yeast’s population is large enough to dominate the liquid, which prevents any other microbes from being active.
How long does the fermentation starter is left until the yeast population is big enough?
about 2 weeks
Is lactic acid the only way to complete the fermentation starter?
- No.
- Other traditional methods do not involve the addition of lactic acid, that take longer time to complete.
How brewer avoid contamination in the main fermentation, not dilluting the fermentation batch without adding additional acid?
they build the main fermentation by stages, maintaining a big enough yeast population to against contamination caused by other undesirable microbes.
How long does it take for the yeast to fully mulitiplied when building the main fermentation?
4 days.
Describe how the main fermentation builds in each of the 4 days.
Day 1 - 1/6 of the ingredients are mixed together, including the small portion of the fermentation starter
Day 2 - nothing is added. Allowing the yeast to mulitiply and spread through the whole mixture.
Day 3 - 2/6 of the mixed ingredients are added. yeast continue to multiply.
Day 4 - the remaining 3/6 of the mixed ingredients are added. yeast continue to multiply to fill the whole tank.
which 2 processes are happening at the same time during the main fermentation?
1 - the kōji is breaking down the starch to sugars
2 - the yeast is consuming the sugar and creates alcohol, CO2 and heat.
Why it’s important for the brewer to control the koji and yeast processes at their right speed during the main fermentation?
1 - if too much kōji enzymes, too much sugar will be produced, the yeast will not be able to consume all sugar, resulting sake will be too sweet.
2 - if too little kōji enzymes, too little sugar will be produced, the yeast will die before the fermentation completed because not having enough of food.
How the brewer to balance the amount of kōji enzymes, sugar and yeast to the just right amount for the main fermentation?
they need to managed the earlier stages correctly
How long does the whole main fermentation process take?
3 to 5 weeks, depends on the temperature.
the lower temperature, the longer it takes.
When the fermentation has reached the desired level of alcohol and sweetness, how the brewer stop the fermentation?
by chilling the liquid to a low temperature that the yeast stop working.
What is the typical alcohol level after the main fermentation?
typically 17% abv to 20% abv
Are all sake has unfermented sugar after the main fermentation?
Yes, nearly all sake has it.
What is the duration of soaking for styles other than the purest and most delicate?
- a few hours in a large tank for other styles that are not the purest and delicate.
Why polished rice cannot convert starch to sugar like beer malt?
the bits that could have grown into a plant have been removed, together with any starch-converting enzymes.
Why koji needed to be made in a special koji room?
The koji room’s temperature and humidity can be managed to help the koji mould to achieve the perfect level of mould-growth.
What is the overall temperature range for sake fermentation?
6C - 18C
How fermentation temperature affects the final style of sake?
By running the upper or lower end between 6C-18C will affect the final style.
How low temperature fermentation affect yeast activities and final style of the sake?
- yeast works more slowly and under stress in cold temperature
- resulting sakes are lighter-bodied, more floral/fruity flavours like: green apple, fresh banana
- usually referred to as ginjō.
How warmer fermentation temperature affect the yeast activity and final style?
- yeast works faster
- resulting sakes tend to be fuller-bodied, more rice/cereal and spicy/earthy flavours.
What does the fermentation looks like when it’s stopped?
- looks like an alcoholic porridge
- because the rice solid that remain
What is inside the alcoholic porridge when the fermentation is stopped?
a large population of inactive yeast
How is the fermentation stop?
by chilling to a sufficiently cold temperature.
What is needed to make a clear, stable sake from the alcoholic porridge?
by passing the liquid through a mesh that holds back the solid parts.
What is filtration?
passing the fermentated liquid through a mesh that holds back the solid parts, in order to get a clear, stable sake.
When does the brewers add distilled alcohol (jōzō)?
After fermentation but before filtration
Why the brewers add distilled alcohol (jōzō) before filtration?
because sake flavours dissolve more in alcohol than in water.
What is the purpose of adding jōzō?
The extra alcohol helps extract more flavours from the remaining rice solids into the sake.
What is the % abv range after adding water into the sake after fermentation?
15 - 17% abv.
What is the sake called if water is not added?
Junmai
Other than using mesh, what other method can be used for filtration?
putting the fermenting porridge into bags and hanging them up, let the clear liquid drip slowly, this method uses just gravity.
What is the disadvantages of using the bag hanging method for filtration?
it’s labour-intensive.
What colours is the filtered sake?
pale lemon-green or lemon colour.
How brewers remove the colour after filtration?
by using charcoal filtering.
What’s next after filtration?
Most sake is stored at the brewery (either in bottle or tank) for a few weeks or months.
Why the finished sake need to be stored in the brewery before release?
to allow the flavours to become more balanced before it’s released.
Which 2 things can cause a sake to develop faulty or unpleasant aromas after filtration, during storing.
1- microbial contanimation
2- chemical reactions
Why filtering cannot prevent microbial contamination?
- Because filtering is not always successful to remove all the yeast completely.
- some brewers do not use such sophisticated filters.
- therefore bacteria and microbes is possible to find their way into the sake
How microbes contaminate the sake if not filtered completed?
- some alcohol-toleratant bacteria can feed on the remaining sugars
- this will create faulty aromas
How chemical reactions contaminate the sake if not filtered completed?
the koji enzymes are not removed by filtration, which will continue to convert leftover starch to sugar that will create unpleasant flavours.
How brewers kill the microbes and destroy the koji enzymes?
by heating the sake to a high enough temperature for a long enough period.
Usaully, sake is heated how many times before release?
twice
When the sake is heated (pasteurized) before release?
1- before tank storage
2- just before bottling or once it’s bottled.
What is used to ensure no further risk of contamination in the sake after pasteurization?
using the seal on the bottle.
What is the other way to avoid the microbes and enzymes active?
by chilling the sake to a very low temperature.
What is the risk of chilling the sake to prevent microbes and enzymes being active?
once the temperature rises, the microbes and enzymes will become active again.
Why brewers still want to release unpasteurized (nama) sake?
because they have a unique lively and fresh character.
How Nama-zakes should be stored?
- Nama-zakes generally have a short shelf life.
- They must be kept refrigerated to avoid rapid spoilage to retain their fresh, lively character.
What is commonly added to the sake at the bottling stage? Why?
- small amount of water
- to adjust the sake to 15 - 17% abv.
After storage and bottling, what is next?
The sake is ready to be labelled and transported for sale.
how the rice ready to steam is loaded inside the steamer?
it’s loaded in layers.
Where and what condition are normally initial koji mould growth take place?
- in the warmest and most humid part of the koji room
- on large tables
Where and what condition is for controlling and stopping the koji mould growth?
in the cooler, less humid areas of the koji room.
What are the choices brewers need to consider after filtration? And what are the styles affected?
1- Amount of filtration: sei-shu or nigori
2- Charcoal filtering: clear sake or muroka
3- Pasteurization: normal or nama-zake
4- Dilution: normal sake or genshu
5- Extended storage: normal sake or koshu
What are the choices brewers have when making fermentation starter (shubo/moto)?
- shokujo-moto (adding lactic acid)
- kimoto or yamahai (adding lactic acid bacteria)
