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)
What is Pyruvic Acid?
The anaerobic digestion of glucose and can be left in sake if the brewer cuts off fermentation early leaves sour taste
What are the average end fermentation temperatures, ABV and sugar levels for sake?
3-5°C
17-20% ABV
15-25 g/L residual sugar
For ginjō fermentation what are the tightly controlled temp ranges per day?
0.3-0.5°C
How do you make a rich, high-umami style?
Polish Ratio - 70%+ (more protein)
Kõji: sõ-haze koji (protein + nutrients = amino = umami)
Temp - high end 16-18°C (vigorous, high acid, lower aromas)
Time: 21-28 days
Good for futshiū-shu and junmai
How do you make a ginjõ?
Polish Ratio - <60% (no/low protein)
Kõji: Tsuki-haze (low protein = low nutrients = yeast struggle = light esters)
Temp - high end 8-12°C (struggle, low acid, esters aromas)
TIme: 30-35 days
Good for futshiū-shu and junmai
Ideal size of ginjõ production and output?
600-1500kg polished rice
800-1200L water
= 720-1800 sake
1kg of polished rice can make how much junmai ginjõ and junmai?
2.5L for junmai ginjō
2.6L for junmai
How much bigger production is Futsu-shu
20-30X
1kg of polished rice can make how much Futsu-shu?
5L with jōzō added
What does sake generally look like after fermentation and after filtration?
Post fermentation a white, opaque liquid full of rice
After filtration clear, pale-green color.
After charcoal clear, water-white
What is the brewer’s aim end of fermentation with jōzō and filtration?
1.Stop at desired ABV and residual sugar
2. max desirable components
3. reduce the coarse components as much as possible
4. Extract the amount of sake to match intended style
How can a brewer achieve its aim post fermentation, eg what tools?
- temp control
- add high-strength distilled alcohol to extract desired aromas
- Use filtration to match style
What do brewer’s check when stopping fermentation
- drop temps to 3-5°C to stop yeast
- Pyruvic Acid check to make sure most has been used during glycosis fermentation
What is pyruvic acid?
During glycosis fermentation glucose is broken into 2 pyruvic acid molecules which are then broken down into ethanol and CO2
What is permitted addition for premium sake before and after filtration?
Before = jōzō, water, rice and koji
After only water
What is permitted addition for futsu-shu sake before and after filtration?
Before = jōzō, water, rice and kōji
Plus sugar for sweetness
Acids for acidity
amino acids for umami
After only water
What is most jōzō from?
Brazil & S. America, made from molasses and other grains. Must be agricole
95%ABV+ reduced to 30-40% in Japan
What are impacts on style with jōzō
- increased expression of delicate aromas eg ginjōs
- Lighter palate (all things in original sake dilutet - acidity, umami, body, sugar)
- More kire finish
- Better STABILITY in sake
Does jōzō increase alcohol in sake and why?
No jōzō does not increase alcohol since it is offset by the addition of water
Overall what does jōzō add to the sake?
Lighter, leaner, purer and more elegant since other compounds are diluted (acid, sugar, body, umami, etc)
What is the alternative to using GNS for jōzō?
Sochu
What is an aruten sake?
jōzō addition
What is the 4th addition?
Technique to control balance using water, sugars and dextrins from steamed rice (eg adding kōji enzymes directly)
When is the 4th addition made
end of fermentation
But no legal limits on timing or additions of water, rice, kōji and yeast during fermentation
What is typically added during the 4th addition
- water, koji, dextrins steamed rice
Can add glutinous rice or sake-kasu.
What is the goal of the 4th addition?
Use kōji enzymes to convert starch into more sugars and leave dextrins (starch fragments)
What are considerations for the sake brewer during the 4th addition?
- how much sweeter to make the sake
- volume since there will be an increase when adding jōzō and water later.
What is sake-kasu?
Solid cake leftover from filtration
Undissolved rice and yeast with 8% ABV
Highly nutritious
Can be eaten, used in cooking, used to make sochu
What is Kasu-buai
mass of sake-kasu as % of mass of polished rice
eg 100kg rice, 25kg sake-kasu = 25% kasu-buai
When is Kasu-buai high?
Ginjōs
1. low temp, low kōji enzymes
2. gentle filtration when rice is brokenup more and less pressure on the presses
When is kasu-buai low?
Futsu-shu - when a lot of the rice is dissolved and the filtration is more powerful like Yubata which presses everything together
What does a 30% or lower kasu-buai indicate?
It is a futsu-shu since most of the rice mass was turned into sake. the filtration press squeezed out most of the sake.
What is the idea of filtration?
It is not pressing per se but rather the using a mesh to separate the liquid from the solid using some pressure or in somecase drip
What are the 3 methods for filtration?
- Yubata/Assakuki - accordion vertical press
- Fune-shibori - bags laid in a funa (box) horizontally presses
- Fukuro-zuri - drop press
Describe assakuki process?
- A Yubuta (brand) machine is a vertical press
- Porridge sake from fermentation pumped into vertical pockets
- Empty panels are filled with air to squeeze the sake porridge
- liquid is squeezed through the fabric and sake-kasu remains in bag
Why is a Yabuta the most widely used machine?
- Extract large volumes quickly
- takes a couple hours
- Strong metal frame allows to squeeze out more sake leaving compressed sake-kasu
- Can adjust pressure for more delicate sakes
- Minimal oxidation
- Industry standard from futsu-shu, honjōzō, and junmai - ginjō and daiginjō sometime made
Describe a fune-shibori?
- Long cloth bags filled with sake
- Bags laid horizontally on top of one another in a funa-rectangle box
- pressure applied from weight on top of the bags to squeeze out sake
- takes 2 days
What are the downsides to Fune-Shibori?
Takes 2 days
Labor intensive
Potential hygiene issues with each bag
Slower extraction = smaller scale
O2 exposure a problem
Used for ginjō, junmai ginjō,some daiginjō and junmain daiginjō
What is Fukuro-zuri?
Hanging bag drip filltration
Describe the Fukuro-zuri method?
- 5-10L bags are filled with sake porridge
- Hung and drip into 18L bottles (to-bin)
- are fractioned filtration and very precise
Challenge with the Fukuro-zuri?
- Small scale
- Labor intensive
- Time consuming takes days
- exposed to O2
Benefits of Fukuro-zuri?
- Very gentle
- Very precise
- Finer textures
- Used for top competitions
What are goals of modern sake filtration?
Brewers are seeking to reduce O2 exposure and using centrifuge, vaccum and stainless steel tanks
Define the 3 fractions during filtration?
- Arabashi - free run - livelier with dissolved CO2
- Naka-dori - Middle fraction - best quality, silky pure
2a To-Bin Gakoi - 19L from Fuku-zuri - Seme - Final Fraction - coarser since pressure is pushing in aminos, lipids, dextrins leading to more bitter, astringency taste
What happens after filtration?
Some sakes are bottled and sold
However, the bulk go through finishing process
What are the options to a brewer for finishing?
- Subtracting - sediment / fining
- Pasteurization (hire)
- Storage/Maturation
- Additions
What cannot be subtracted and what can be added after Filtration?
Alcohol = no
Water = yes (unless genshu)
What is sake haziness usually attributed to?
Small particles of yeast or rice, sometimes protein
What are subtraction techniques?
- Sedimentation (ori-biki) - yeast/rice settles top liquid pumped out
- Protein fining - use persimmon or gelatin to capture protein
- Activated charcoal or diatomaceous earth (roka) - slows aging, color and aroma development
- Micron filters - for water white
- Molecular sieve - captures enzymes and no need to pasteurize
For shinzuku-zake where does sedimentation take place?
In the to-bin (bottle)
What is the challenge with protein during filtration?
Too small for a filter
Get suspended in sake
Require fining agent like persimmon or gelatin to clump the protein together and settle
Why use charcoal?
To reduce color that is left over from kōji
Undesirable aromas, flavors and texture
How is charcoal powder used in fining?
ROKA - 1911
1. Charcoal powder is added to the tank and unwanteds are absorbed on the surface
2. Diatomaceous earth is added to avoid charcoal blocking the filters
3. paper or cloth filter is used to remove both
slows aging, color and aroma development
Why did charcoal fining become a big thing?
Started in 1911
But 1980s - Niigata style was big
Light, crisp, dry and water white
What is muroka and why is it now popular?
No use of charcoal
Brewers thought positive sake character being stripped out and too thin
What is su-roka?
Natural fined sake using only earth and not charcoal
Why use micron filters?
Small pores strip out most things
1. Produces crystal clear sake
2. improves stability by removing yeast and bacteria
PROBLEM - can get clogged easily and doesnt remove enzymes
What are options to stop micron filters from getting clogged?
- Use earth as a first filter
- use cross flow filter.
What is a molecular sieve?
Semi-permeable membrane which removes enzymes and no need for pasteurization
What additions are made?
Only water
Sake is usually 17-20% ABV so brewers add water to reduce by 1-2% ABV
If no water added = genshu
Why would a brewer blend?
- For consistency that cant achieve in a single batch
- New styles - eg polish ratios, koji types, age, press fractions, lees, storage methods etc
Why is pasteurization required (hire)?
Sake is not stable and can deteriorate
1. kōji and dextrins still in sake and can keep converting to sugar
2. Yeast can still ferment the remaining sugars
3. Low acidity so other microbes can get busy
4. No SO2 is allowed
What is not allowed as a preservative for sake?
SO2
What is hi-ochi-kin and why is it a problem?
A lactic acid bacteria
Can cause cloudiness, oxidize and create bad odors
Options to remove kōji enzymes in finishing?
Either a molecular filter (expensive)
or pasteurize
What temp and types of pasteurization?
60-65°C
1. Bulk in a tank - most efficient
2. Bottled then in hot water - labor
How does bulk pasteurization work?
Usually through a heat exchange with liquids flowing opposite directions
What is ja-kan?
Traditional bulk pasteurization
A coiled pipe with sake flows through hot water and into a tank
Takes 2 days to cool not good for ginjōs since loses subtle flavors being hot for so long
What are modern bulk pasteurization process?
Using heat exchange with hot and cold. Sake pass through hot water and then cooled immediately after pasteurization.
PROBLEM - careful not to contaminate on the cooling
What is bin-hire
Bottle pasteurization
How does traditional bin-hire work?
- Sake bottled 1st
- Immersed in 65°C water
- Then cooled immediate with cold shower 30°C
SINCE SAKE IS BOTTLED NO NEED FOR 2nd Pasteurization
Quick, gentle but labor intensve
Nama-zake or shinshu?
Unpasteurized (new sake)
Only seasonal
extremely sensitive to heat
Risk of hi-ochi bacteria
What 3 options are available to brewers who want to maximize “freshness” of nama-zake but with some pasteurization
- Nama-chozō - 1X pasteurized in bulk form after storage
- Nama-zume - 1X pasteurized in bulk form before storage in bulk
- “once-pasteurized” - 1X before storage in bottle
Why rest sake?
6-12 months since sake is still “rough”
Balances flavors and textures usually in tanks 10-20°C
ginjōs stored in bottles
Difference between koshu and jukusei-shu?
Koshu 2+ years aged
Jukusei-shu - used for any aged sake at low temps become silkier - ginjōs stored below freezing
