Basics of Sake Production Flashcards
Understanding Sake: Explaining Style & Quality Chapters 1 & 2
What is sake?
An alcoholic beverage made from polished (white) rice with water and kōji, fermented with yeast.
What is the typical alcoholic strength of sake in comparison to distilled spirits?
Sake: 15-17% abv
Spirits: 40%+ abv
Aside from fermentable sugar, which components are present in grapes (and thus wine) but not in rice (and thus sake)?
Grapes -
- High acidity
- Distinct aromas and flavours that are present in the final wine
- Colour pigments
- Tannin
Rice -
- Low levels of acidity
- Little flavour
- No colour pigments
- No tannin
In beer production, how is starch converted to sugar?
Whole unpolished grains (usually barley) are encouraged to germinate. The grains produce enzymes that convert starch to fermentable sugar. Grains are heated to stop the conversion process.
> Malting
Malt can be toasted, dried with smoke, or charred, which adds extra flavours
In sake production, how is starch converted to sugar?
Polished grains of rice are used. They cannot be encouraged to germinate as the part that would grow into a plant is removed during the polishing process.
Kōji mould is grown on steamed rice, producing enzymes that convert starch to sugar.
Kōji has very little flavour other than a delicate sweetness.
Can sake be flavoured with other ingredients?
If sake is flavoured with other ingredients it can no longer legally be called sake.
When is rice planted, grown and harvested?
Planted in spring
Grown in summer
Harvested in autumn
How is rice grown?
Either in flooded rice paddies or sometimes farmed in dry fields (latter is common in USA)
What are the two main subspecies of rice?
Indica - long grain
Japonica - short grain
What are the two types of Japonica rice?
Sticky/glutinous
Non-sticky/non-glutinous
Which type of rice is used for sake production?
Non-sticky Japonica (short grain)
What is table rice?
High yielding and easy to farm non-sticky Japonica rice. Grown as table rice for eating, but also suitable for sake production.
What are the typical characteristics of sake rice? List the positives and negatives.
Negatives -
- Harder to farm
- Lower yields
Positives -
- Less protein than table rice
- Most of the starch granules are in a pure core at the centre of the grain
- Larger grained, so less likely to crack when polished
Why is the rice polished?
To remove protein, lipids, vitamins and minerals present in the outer part of the rice grain.
Any protein, lipids, vitamins and minerals that remain will impact the style and category of the sake.
What is present in the outer part of the rice grain before polishing?
Protein
Lipids
Vitamins
Minerals
Any protein, lipids, vitamins and minerals that remain after polishing will impact the style and category of the sake.
What is the polishing ratio?
The amount of rice that remains after polishing
What happens after polishing?
The rice grains are cleaned to remove any remaining rice powder. The rice is washed in small containers, large vats or a continuous rice polishing machine, depending on the size of brewery and style of sake.
The powder is made up of the outer layers of the grain and if it were used, would make the resulting sake less pure, more acidic and rough-textured
Describe the style of sake made from highly polished rice.
Pure Fruitier flavours Lighter body Lower acidity Lower umami
> this is not necessarily of higher quality, just a different style, although prices tend to be higher.
Describe the style of sake made from coarsely polished rice.
More savoury Less fruity More body More acidity More umami
> this is not necessarily of lesser quality, just a different style, although prices tend to be lower.
Put these actions that occur at the start of sake production into order:
Soaking
Washing
Steaming
Polishing
Polishing (to remove proteins, lipids, vitamins and minerals)
Washing (to remove excess power and impurities)
Soaking (to alter the amount and distribution of water in the grain)
Steaming (used rather than boiling so that the outside of the grain remains firm)
How long is the sake rice soaked for, prior to steaming?
This depends on the style of sake.
For the purest and most delicate sake, a stopwatch is used and the rice is soaked in small batches for a few minutes.
For other styles, there is less need to be so precise and soaking is done in large vats for a few hours.
How is the rice steamed after soaking?
Steamed in batches of approximately 1 tonne for 1 hour.
Large brewers have rice steamers that run continuously and are larger and faster.
How long are pure and delicate sake styles soaked for?
In small batches for just a few minutes (timed using a stopwatch)
How long are more robust styles of sake soaked for?
In large vats for a few hours
Why is the rice soaked and steamed before fermentation?
- Raises moisture levels within the grain to produce the best kōji
- Heat changes the structure of the starch so that kōji enzymes can break it down
- Disinfection of the rice, undesirable microbes are killed.
Soaking and steaming raises the moisture levels in the rice. Why is this important?
Soaking ensures that the rice absorbs enough moisture to be soft and moist on the inside.
Steaming rather than boiling ensures that the outside of the rice grain remains firm
These methods ensure that there is even distribution of moisture for producing the best kōji, and makes sure that the rice breaks up in the ferment at the correct rate.
Soaking and steaming changes the starch in the rice. How does this occur and why is this important?
The heat of steaming changes the structure of the starch.
This allows the kōji enzymes to break the starch down into fermentable sugars. Without heat, the kōji enzymes cannot break down the starch.
Soaking and steaming disinfects the rice. Why is this important?
The heat of steaming kills microbes that may cause contamination of the ferment.
What is starch?
A large molecule made up of lots of sugar molecules all linked together in a chain
What is an enzyme?
A type of protein that helps chemical reactions to take place without being used up in those chemical reactions. This means that only small amounts of enzyme are required to convert a lot of starch to sugar.
What is kōji-kin?
A mould (Aspergillus oryzae) that grows on the outside of rice, creating starch-converting enzymes
What percentage of the rice used for sake brewing is converted into kōji?
One fifth to one quarter
What are the ideal conditions for kōji mould to grow?
High humidity
33-38°C
What is the kōji room?
The area of the brewery where kōji mould is grown. The temperature and humidity can be controlled to speed or slow the growth of the mould.
What are the four steps of kōji mould production?
Cooling
Inoculation
Initial mould growth
Controlling and stopping mould growth
What occurs during the Cooling step of kōji mould production?
The portion of steamed rice that will become kōji is cooled to the right temperature.
What occurs during the Inoculation step of kōji mould production?
Cooled steamed rice is transferred to the kōji room and spread thinly on a table. Kōji mould spores are sprinkled on it
What occurs during the Initial Mould Growth step of kōji mould production?
The warm and humid conditions in the kōji room encourages the spores to grow into mould and spread across the grains of rice. The rice is thoroughly mixed to ensure growth is even.
What occurs during the final step of kōji mould production?
Controlling and stopping mould growth -
The rice is sometimes transferred to racks and moved to a cooler and less humid part of the kōji room. The temperature of the room must be controlled so that the correct amount of mould is grown on each grain. Mould growth is stopped by moving the rice to the driest and coolest part of the room.
How long does the kōji process take?
About two days
How is kōji mould growth stopped?
The rice is moved to the coolest and driest part of the room
Why is kōji mould growth strictly controlled?
The amount of kōji on the grain impacts the style of sake produced.
High levels of kōji mould on the grain means that large amounts of enzymes are produced. The starch is rapidly transferred to sugar. Fermentation is faster. The sake has more acidity, flavour and umami.
Low levels of kōji mould on the grain means that lower amounts of enzymes are produced. The starch is slowly transferred to sugar. Fermentation is slower. The sake is lighter in flavour, with less acidity and umami. This style of kōji is used for the purest, most delicate ginjō.
What percentage of the final sake product is water?
Over 80%
What type of water can be used for sake?
Any clean, low-iron water.
The level of minerals in the water impacts fermentation and thus sake style.
Why are special yeast strains required for sake fermentations?
- The yeast must keep working even when the alcohol level is high (up to 20% abv)
- The yeast must be able to work in cold conditions (ginjō sake may be fermented as low as 6°C)
- The yeast must be able to work at low sugar/nutrient levels (ginjō sake has very low sugar levels)
- Selected yeast strains may be chosen for desirable properties such as reliability or production of aromas.
What are the four key steps of sake production?
The fermentation starter
The main fermentation
Jōzō alcohol and filtration
Finishing
Why is the initial mixing of steamed rice, kōji, water and yeast together a risky stage of production?
The kōji enzymes start to convert starch to sugar, but it takes time for the yeast population to build up. Other undesirable microbes (yeasts, moulds, bacteria) could settle in the liquid, consuming sugars and spoiling the sake.
What method is used to prevent initial spoilage of the steamed rice, kōji, water and yeast?
The creation of the fermentation starter
What is the fermentation starter?
A small portion of steamed rice, kōji, water and yeast is put into a small tank. Lactic acid may be added to allow acid-tolerant sake yeast to dominate. The starter is left for two weeks to ensure that there is a healthy population of the desired yeast.
How long does the sokujo fermentation starter take to make?
Approximately 2 weeks
Why might lactic acid be added to the fermentation starter?
To allow acid-tolerant sake yeast to dominate, rather than undesirable microbes
What happens on Day 1 of the main fermentation?
One sixth of the total steamed rice, water and kōji are mixed together (including the fermentation starter)
What happens on Day 2 of the main fermentation?
Nothing is added.
The yeast multiply and spread through the mixture
What happens on Day 3 of the main fermentation?
Two sixths of the total steamed rice, water and kōji are added, and the yeast continues to multiply
What happens on Day 4 of the main fermentation?
The remaining three sixth of the steamed rice, water and kōji are added, and the yeast continues to multiply.
The saccharification and alcoholic fermentation will now happen at the same time.
What happens if there are too many kōji enzymes in the fermentation?
The starch will break down into sugar at too fast a rate and the yeast cannot consume it all. The resulting sake will be too sweet.
What happens if there are too few kōji enzymes in the fermentation?
The yeast will run out of sugar and die.
How long does the main fermentation take?
Three to five weeks, depending on the temperature.
What happens when the fermentation reaches the right balance of alcohol and sugar?
The brewer intervenes to stop the fermentation.
The liquid is chilled to stop the yeast from fermenting
True or false:
Nearly all sakes have some unfermented sugar.
True
What is the level of natural alcohol after the fermentation?
17-20% abv.
It can be lower.
At what temperature is sake fermented?
Quite cool
6°C to 18°C
How does a warmer fermentation temperature affect the style of sake?
Note body and flavours.
At the higher temperatures, the yeast works more quickly. The sakes are fuller bodied, with rice/cereal and spicy/earthy flavours.
(Most sake is fermented at 6°C to 18°C)
How does a cooler fermentation temperature affect the style of sake?
Note body and flavours.
At the lower temperatures, the yeast works more slowly. The sakes are lighter bodied, with floral/fruity flavours
(Most sake is fermented at 6°C to 18°C)
Why do ginjō styles have distinct green apple and banana aromas?
A very long, very cold fermentation puts the yeast under stress. The yeast produce chemicals that have aromas of green apple and banana.
If a brewer chooses to add jōzō alcohol, when would he add it?
After fermentation is stopped, but before filtration
Why is sake filtered after fermentation?
To remove rice solids and (now inactive) yeast.
What is jōzō?
Pure alcohol distilled to 95% abv
Why might jōzō be added to a sake?
Flavours are more soluble in alcohol than water.
If jōzō is added before filtration, the flavours will remain in the sake rather than in the rice solids.
Why is sake rested in either bottle or tank before it is released?
Resting allows the flavours to become more balanced.
Name two things that can cause sake to develop faulty or unpleasant aromas.
- Microbial contamination (alcohol tolerant bacteria can feel on remaining sugars)
- Chemical reactions (kōji enzymes are not removed via filtration and can continue to convert leftover starch to sugar, causing unpleasant flavours)
Sake can develop faulty or unpleasant aromas. What process is used to avoid this?
Heat sterilisation
Kills microbes and destroys kōji enzymes
How is sake heat sterilised?
Either once or twice.
- in the tank
- in the bottle
What is the alcoholic strength of jōzō arukōru?
95% abv
True or false:
Jōzō must be sourced from within Japan
False
