Learning Objective 1 - Fermentation - Post-Fermentation Flashcards
What is shubo or moto and what is the brewers aim to create this?
A fermentation starter
Goal to create enough lactic acid to inhibit other microbes eg bacteria or other yeast and allow brewer’s yeast to thrive. Then used in main fermentation
How is shubo created
- small tank 6-10% size of main
- Rice,Koji & Water (Koji 30%)
- 14-28 days to develop
- Must maintain temp and acidity
What is the ideal temp to create shubo?
10°C Keeps bad microbes from growing
What are criteria for a shubo room
- Cool Temps 10°C
- Hygienic - keep clean
- Isolated from Brewery
- Well ventilated
Why is temperature control so important in shubo?
Need to maintain a balance between the kōji enzymes creating glucose and the yeast using that as food to multiply. Eg do not want the yeast to run out of food.
What are methods of temperature control?
Daki - bucket for hot of cold water
Cooling pipes,
Ice on outside - held by jackets
Ice replacing water
Foot warmers
Heat lamps
What is the acidity issue with shubo?
-Steamed rice, water and koji do not have enough acidity.
-kōji takes time to create sugars
-bacteria multiplies faster than yeast
SOLUTION - add lactic acid
What are the ways to add lactic acid to shubo?
Kimoto - bacteria creates lactic
Yamahahi - bacteria creates lactic
Sokujō-moto - brewer adds lactic
What is Sokujō-moto?
“Quick Fermentation”
Started 1900s when they started adding lactic acid
How to make Sokujō-moto?
- Soak kōji for hours
- Then add get lactic acid (<1%), yeast and steamed rice
- Keep temps 18-25°C good for kōji and yeast
- start pumping over liquid as rice is still hard
- Day 2 cool to 10°C
- Day 3-7 let temps zig-zag by 2-3°C = increases kōji saccharification and yeast multiplying
- then let shubo increase to 23C until day 13
- Day 14 cool to 7°C with 11-12% ABV
How to increases kōji saccharification and yeast multiplying during shubo production?
Let the shubo increase in temps 2-3°C then fall 1-2°C
Warming increases yeast
Cooling increases saccharification
What is the final ABV of shubo Day 14
11-12% ABV
Why do Sokujō-moto
- Quicker 14 days v 28
- Better precision control
- Shorter time and avoids need for a bacteria to create lactic acid
- Flavor profile is purer, less acidic and has complexity
What are other forms of Sokujō-moto?
Middle Temperature = dont cool, cuts time to 7 days
High-Temp (Kō-on tōka) = used in Hiroshima or warmer climates
What Sokujō-moto method would you use if you want a lighter and cleaner sake?
Middle Temperature
Describe Middle Temperature Sokujō-moto?
Simplified version of Sokujō-moto
Start at 20-25°C and never cool
No use for a Daki
7 days total
Lighter and cleaner sake
Why use High Temp Sokujō-moto?
Kō-on tõka
-Day 1 - 55-60°C add koji and steamed rice - Sterilize and speed up sugar conversion
-Hours 8 drop to 40°C and add lactic acids
- Add yeast when temps are 25-30°C
-Temps lowered until Day 7 (18°C)
Very efficient, very pure, clean sake
What is the challenge with Kō-on tōka?
High Temp Saccharification
Need to bring the higher temps of the shubo down rapidly to 25-30°C in order to avoid external microbial contamination
What style does Kō-on tōka create?
High Temp Saccharification
Very pure and clean sake
Advantages of Sokujō-moto?
Quick
Precise
Less risk of spoilage
Consistency
Cleaner flavors less umami
What are the challenges to Kimoto and Yamahai?
Increased risk of spoilage when acid is being produced
What are advantages of Kimoto and Yamahai
-Builds stronger yeast population
-Extra flavor & richness
-Higher avidity
-Can create O2 flavors caramel/nuts
What is the brewers aim for shubo?
- Safe enviro for yeast growth
- Healthy yeast population
What is kimoto and yamahai?
Pounding rice
Kimoto is the ancient (1600s NADA) fermentation starter
Yamahai is newer early 1900s
Use lactic bacteria to create the lactic acid for main fermentation
Yama-oroshi
Process. of pounding steamed rice, koji and water (Kimoto)
Kimoto Process
- keep temps low 6-7°C to keep right type of bacteria
- Say 2 use pole to pound rice, H2O, Koji in tubs to paste
- this breaks up rice, increases enzyme contact
- Day 3/4 temps lower 5-6°C for nitrate-reducing bacteria then lactic bacteria to grow
- Day 4/5 start using Daki to increase 2°C and then drop 1°C at night - lactic starts dominating nitrate bacteria
- Day 14, nitrous acid lower and lactic sufficient intro yeast
- Temps rise to 23° and by day 24 cool to 7°C over 4 days
What is difference with Yamahai to Kimoto?
- Start with warmer water 8-9°C soaking kōji 1st
- higher water ratio to attract lactic acid bacteria
- Pump over the mixture on the steamed rice
- Use pole to mix which accelerates rice dissolving
What is difference in outcome from Yamahai and Kimoto?
Same reliability
Less work
What is the challenge for Kimoto/Yamahai?
Potential for increased spoilage
Nitrate reducing bacteria creates the nitrous acid which allows lactic acid bacteria to then thrive.
Too much nitrous acid wont let yeast grow and too little acid over all increases spoilage potential
What are the advantages of Kimoto/Yamahai
- Build strong yeast population
- Extra flavor and richness
- Higher acidity
- Can be combined with O2 flavors eg caramel and nuts
- Yeast can have higher ABV tolerance
Akita Style kimoto
Mr. Kodama 1990s
Uses electric mixer instead of poles for Yamahai
More rapid, less O2, cleaner shubo, lower contamination risk
Other methods for Kimoto/Yamahai?
- Akita - using an electric mixer
- Adding lactic bacteria cultures (not acid itself)
- Plastic Bags “Yama-oroshi”
Yama-Oroshi
Mr. Sato of Akita
Uses plastic bags for rice and koji to create nitrous acid first using hard water which is good for that type of bacteria.
Bags are massaged until appropriate nitrous acid formed.
What is Bodai-moto?
Shorykuji Temple - only in Nara
Uses “sour water”
Miu-moto
How is Bodai-moto (Mizu-moto) made
- steamed & uncooked rice soaked in room-temp water
- Lactic bacteria acid on rice produces acid
- uncooked rice removed and steamed
- Steamed rice & kōji mixed with acid water & yeast for 7-10 days
What is style of Bodai-moto?
- Lactic, cheese, sour milk, yogurt
- Impact can be managed
- Thus sake can be range of styles
What is the aim of the brewer during fermentation?
- avoid a stuck fermentation
- achieve the correct balance between starch conversion (kōji) and alcohol conversion (yeast)
- Achieve desired aromas and texture
What is the main stages of moromi in Japanese?
- Hatsu-zoe - Day 1 - 1st Addition 1/6 added 12-15°C
- Odori - Day 2 no addition
- Naka-zoe - Middle Addition - 1/3 added
- Tome-zoe - Final Addition - 1/32added 6-10°C (add ice)
Standard Ratio for main fermentation
80 Rice
20 kōji
130 H20
Why add rice, kōji and water in stages?
let kōji build up enough glucose for yeast to thrive
Do not want to dilute the yeast population and risk microbes
What is sandan jikomi?
3-stages of additions in moromi
What is liquefaction?
-Make powdered rice
-Steam it
-Mechanically mix with enzymes to break down rice for fermentation
an accelerated and complete enzymatic digestion of rice
-Cost effective for cheap sake
Why use liquefaction (powdered rice)?
Faster production
Avoid Shubo
Less kōji
Higher yields
Cost effective
Cheap
What happens between enzymes and yeast when temps rise?
When temps rise, yeast consumption rises faster than enzymatic digestion meaning the yeast could potentially run out of food or you have less protease hence less umami and a thin sake
What happens between enzymes and yeast when temps drop?
The quantity of enzymes must be lower since the yeast will not be as robust and if too much glucose is formed, it could result in too sweet or a stuck fermentation or extreme cases high levels of volatile acids (bad smells)
Ginjō yeasts?
7 not for aromas but restrained styles
#9 - isoamyl alcohol (banana)
Other yeasts - caproic acid, caproyl
What fermentation temps for a rich junmai and a daijinjō?
Junmai = 16-18°C
Daiginjō = 10-12°C
Why are temperatures lowered at the end of fermentation for all sake styles?
- Stop yeast activity
- End alcohol production
- all to avoid dead yeast which create off aromas
What happens if the brewer stops fermentation too early?
Pyruvic acid is created as part of the conversion process of glucose to alcohol process.
If fermentation stops too early, it can lead to leaving Pyruvic acid in the sake creating sour taste or it is broken down into acetaldehyde (wood taste)