Chapter 2: An Overview of Sake Production Flashcards
What are the ingredients of sake?
Steamed rice, Kōji, water and yeast
What are the two main subspecies groups of Asian rice?
long-grained (Indica) and short-grained (Japonica), which are further subdivided into sticky (glutinous) and non-sticky (non-glutinous).
What type of Asian rice does sake brewers use?
Non-sticky version of short-grained rice.
Can high-yielding, easy-to-grow table rice varieties be used for sake brewing?
Yes
Why are some harder to farm and lower yield special varieties developed for sake brewing?
They make it easier to separate cleanly the starch from the proteins and other undesirable parts of the rice grain:
- they contain less protein than table rice
- Most of the starch lies in a well-defined and almost pure starch core at the centre of the rice
- They are larger-grained, and therefore less likely to crack when polished
Name the processing steps before rice is used in sake production?
- Polishing
- Washing
- Soaking
- Steaming
What is the purpose of polishing rice?
Remove the proteins, lipids, vitamins and minerals that are concentrated in the outer part of the rice grain, leaving just the starchy core.
What is the polishing ratio?
The percentage of rice that remains after polishing
What process happens to the rice grain after polishing? and why?
The rice grain need to be cleaned to remove any remaining fine rice powder. If they remained, thy would make the sake less pure, and more rough-textured and acidic. The powder is removed by washing.
What does the rice polishing ratio (and the relative proportion of proteins, lipids, vitamins and minerals that remain) affect?
The style and the category of the final sake
What are characteristics of a sake made from rice with a low polishing ratio?
Tends to have purer, fruitier flavours and is lighter in body with lower acidity and umami. Sake made from the most highly polished rice can be used to make one of the ginjō styles of sake.
What are characteristics of a sake made from rice with a high polishing ratio?
Tends to have more cereal and less fruity flavours, with more body, more acidity and more umami.
What are the processes after rice is polished and washed?
Soaking and steaming
What are the purposes of soaking then steaming the rice?
- Raising the moisture level within the grain
- Changing the starch
- Disinfection of the rice
What is starch?
A large molecule made up of lots of sugar molecules all linked together in a chain
What are enzymes?
Enzymes are chemical that break up the rice starch into sugars before the sugars can be fermented by the yeast into alcohol. It is a kind of protein that helps chemical reactions to take place without being used up in those chemical reactions, therefore only small amounts of the right enzymes are needed to convert large amounts of starch into sugar
Where are enzymes in the nature world?
Any living thing that can digest starch has them. Starchy cereal grains also have enzymes to convert their space-efficient starchy store back into sugar before they can use that sugar to provide energy to grow into a plant.
Does sake use malted grains like beer to convert starch into sugar?
No. Sake is made from polished rice: the bits that could have grown into a plant have been removed, along with any starch-converting enzymes. Therefore, a mould that creates starch-converting enzymes is allowed to grow on some of the rice. This mould is called kōji mould and the mouldy rice is called kōji.
What is kōji?
Mouldy rice, where the kōji mould creates starch-converting enzymes.
What’s the proportion of rice in sake brewing is converted into kōji?
About 1/5 or a quarter
What are the ideal conditions for kōji mould?
High humidity and warm temperatures of between 33 degrees and 38 degrees.
What are the four main objectives in the process of making kōji?
- Cooling (Step 1): the portion of steamed rice that will become kōji is cooled to the right temperature.
- Inoculation (Step 2): the cooled steamed rice is transferred to the kōji room and spread out thinly over a table. Kōji mould spores are sprinkled on it.
- Initial mould growth (Steps 2-3): the warm and humid conditions in the kōji room encourage the spores to grow into the mould. The mould spreads and grows over all of the grains of steamed rice. The rice is thoroughly mixed to ensure that the growth of mould is even.
- Controlling and stopping the mould growth (Steps 4-7): The rice is then sometimes transferred to racks and moved to a cooler, less humid location in the kōji room. The aim of the brewer is to control the temperature in order to slow the mould growth so that exactly the right amount of mould can be grown on each grain. Ultimately the mould growth is stopped when the rice is finally moved out of the kōji room to a location that is cool and dry. Fans are sometimes used to help with the cooling process.
How long does the whole process of making kōji take?
about 2 days
Describe the finished kōji.
Looks like polished rice but has a crumbly texture, a delicate roasted chestnut aroma and is slightly sweet.
Describe the different styles of kōji.
- kōji with high levels of kōji mould enzymes — large amounts of kōji mould covering and penetrating the entire grain, means that large amounts of enzymes and nutrients are secreted. Therefore, starch is more rapidly converted into sugar in the fermentation tank. As a result, the fermentation is faster, and the sake tends to have more flavour intensity, with more acidity and umami.
- kōji with low levels of kōji mould enzymes — tiny amounts of kōji mould, dotting the outside of the grain, means that smaller amounts of enzymes are created. Also, because much of the growth occurs within in the grain (rather than on the surface), the enzymes are released more slowly into the fermentation. Consequently, there is a slower conversion of starch into sugar during the fermentation. The fermentation is therefore slower, and the sake tends to be lighter in flavour, with less acidity and umami.
This style of kōji requires extreme precision during the rice polishing, washing, soaking and steaming, as well as in the kōji room. Therefore typically used in order to produce the purest, most delicate styles of ginjō.
Why do sake brewers add water?
To make rice into a fermentable liquid
How much of the final sake is added water?
Over 80%
What types of water can be used for sake brewing?
As long as it is clean, and iron concentration is low, almost any water can be used.
Does water affect sake style?
Yes. Mineral concentration affects the fermentation and therefore the style of the sake.
What are the particular conditions of sake fermentations that require special yeast strains?
- they must keep working when the alcohol level is high (can be over 20% abv)
- often have to work in cold conditions (e.g., the fermentation temperatures for ginjō sakes can be as low as 6 degrees)
- limited supply of food (ginjō fermentations can have very low levels of sugar)
How does the industry identify certain yeast strains for sake fermentation
- can work at higher alcohol levels
- tolerate cold temperature
- tolerate low food supply
- desirable properties, such as being very reliable or producing interesting aromas
What do yeast contribute to the sake?
In the absence of distinct aromas and flavours from the rice, yeast contribute greatly to the aroma in most sakes. Some strains have very distinct characteristics and a chosen because of the particular aromas they provide.
What are the four key steps of sake production?
- the fermentation starter
- the main fermentation
- jōzō alcohol and filtration
- finishing
Why is it a risk stage after all the ingredients are mixed together?
Kōji enzymes start to turn the rice starch in to sugar, but it takes time for a healthy yeast population to build up. Other undesirable microbes (yeast moulds and bacteria) could settle in the liquid and begin to consume the sugars and spoil the flavours of the sake.
What is the fermentation starter?
To avoid contamination, the brewer takes a small portion of the ingredients and makes a mini fermentation, usually in a separate small tank.
What’s the common way to help ensure the fermentation starter does not become contaminated?
Increase the acidity of the water by adding lactic acid.
Why is lactic acid used to increase the acidity of the fermentation starter?
Sake fermentation yeast are much more tolerant of lactic acid than any of the other spoilage microbes. Therefore, the brewer can be confident that the only microbes that thrives and multiples is the yeast they have chosen
How long is the fermentation starter left for?
Until there is a population of the brewer’s selected yeast that is large enough to dominate and prevent any other microbes from being active. This takes about two weeks.
Are there methods other than the addition of lactic acid?
Yes. Sometimes other traditional methods that take longer to complete are also used.
The main fermentation is build in stages across how many days?
4 Days
Describe the 4 days/stages of building up the main fermentation.
Day 1 - about 1/6 of total steamed rice, water and kōji are mixed together, including the fermentation starter
Day 2 - nothing is added, to allow the yeast from fermentation starter to multiply and spread through the whole mixture
Day 3 - About 2/6 (1/3, twice of Day 1) of the total ingredient are added, yeast continue to multiply to occupy the liquid
Day 4 0 The remaining 3/6 (1/2, Day 1 + Day 3) of the total ingredients are added, and the now vigorous yeast population can multiply to fill the whole tank.
What is parallel fermentation?
Once the main fermentation has been built, two process happens at the same time: the kōji enzymes breaking down starch into sugar to make food for the yeast; and the yeast are consuming the sugar and creating alcohol, carbon dioxide and heat.
Why is it important that the brewer makes sure the two processes of parallel fermentation happen at the right speed?
If the quantity of kōji enzyme is too high, too much sugar is created too quickly, and the yeast are not able to consume all of the sugar, the resulting sake will become too sweet.
If there is too little, the yeast will run out of sugar and die.
How long does the main fermentation take?
About three to five weeks, depending on the temperature. The colder the temperature, the longer it takes.
How does the brewer stop the fermentation process once it reaches the desired level of alcohol and sweetness?
By chilling the liquid to such a low temperature that the yeast stop fermenting altogether
What is the level of alcohol after main fermentation?
Typically ranges from 17% abv to 20% abv, although it can be lower.
True or False. All sakes have some unfermented sugar.
False. NEARLY all sakes have some unfermented sugar.
What is the temperature for sake fermentation?
6 degrees to 18 degrees.
How does fermentation at different temperatures affect the final style of the sake?
Warmer fermentation temperatures - Yeast work more quickly, fuller bodied with more rice/cereal and spicy/earthy flavours.
Colder fermentation temperatures - Yeast work more slowly, lighter bodied with more floral/fruity flavours.
What sake styles are extremely cold, slow, long fermentations used for? What are the characteristics and why?
ginjō. In very cold conditions, with very little food to consume. The yeast are put under great stress, thus produce more higher levels of aromatic chemicals (esters). These have distinct aromas including green apple and fresh banana.
The process of making sake starts with brown rice. What is the first thing that happens to it?
Polishing
What is the key choice a brewer has to make during polishing?
The amount of polishing
Polishing removes the outer part of the grain. The amount that is removed is referred to as the polishing ratio.
100% polishing ratio = brown rice or unpolished rice.
70% polishing ratio = 70% of the rice grain remains.
60% polishing ratio = 60% of the rice grain remains. Rice used in the production of ginjō styles of sake must have a polishing ratio of 60% or less.
50% polishing ratio = 50% of the grain remains. Rice used in the production of daiginjō styles of sake must have a polishing ratio of 50% or less.
What is the next step after polishing?
Washing
What is the next step after washing?
Soaking
What is the next step after soaking?
Steaming
What happens to the steamed white rice?
It is cooled and then it is either added to a fermentation batch or it is used to make kōji.
Kōji is rice that has had mould grown on it. The mould is called kōji mould or in Japanese kōji-kin.
Once the rice enters the kōji room the brewer begins to make kōji, they have three principal objectives during this part of production. What are they?
Inoculation with kōji mould spores, initial mould growth and controlling and stopping the mould growth
What is the principal choice a brewer has to make when making kōji?
The brewer needs to decide on the level of kōji mould enzymes they want in their kōji.
Kōji with a high level of kōji mould enzymes is called sō-haze and it is used in the production of sakes that have a faster fermentation and higher levels of acidity and umami.
Kōji with a low level of kōji mould enzymes is called tsuki-haze and it is used in the production of sakes that have a slower fermentation, lower levels of acidity and umami and intense fruity (ginjō) aromas.
Aside from steamed white rice, kōji and water what is the other main ingredient of sake?
Yeast
What does the brewer make at the start of the fermentation process?
The fermentation starter, shubo, moto
What kind of acid can brewers add to the fermentation starter?
Lactic Acid
What labelling terms are used for sakes that are made without the addition of lactic acid?
Yamahai and Kimoto
True or False: Once the fermentation starter is ready, it is mixed with more water, steamed white rice and kōji in order to make up a full main fermentation batch. These ingredients are all added in one go.
False
What is added on each day and what proportion of the main fermentation batch’s final volume does each addition make up?
Day 1: 1/6 starter, kōji, steamed rice, water
Day 2: nothing
Day 3: 1/3 kōji, steamed rice, water. Total fill 1/2
Day 4: 1/2 kōji, steamed rice, water. Total fill full
What do some brewers add immediately after fermentation?
Jōzō alcohol
What does the term junmai mean?
Junmai indicates that jōzō alcohol has not been added. Junmai can also be used in conjunction with labelling terms that indicate polishing ratio. The two examples are junmai ginjō (polishing ratio of 60% or less) and junmai daiginjō (polishing ratio of 50% or less).
After fermentation what happens next?
Filtration
Can a brewer skip the filtration step?
No, all sakes must be filtered. A brewer can choose how much of the solid material left in the fermentation they want to remove. The vast majority are clear.
What labelling term indicates that a sake is cloudy?
Nigori
Are the majority of sake charcoal fined?
Yes
What is the labelling term that indicates that a sake has not been charcoal fined?
Muroka
What is the process that can happen to a sake either once or twice during its period of storage at the brewery?
Pasteurisation
What is the labelling term that indicates that a sake has not been pasteurised?
Nama
What do the vast majority of brewers add to their sakes prior to packaging?
Water
What is the labelling term that indicates that a sake has not been diluted with water?
Genshu
What is the labelling term that indicates a sake has been stored for an extended period at the brewery?
Koshu
