Koji:
the mold at the heart
Meet the organism that makes sake possible at all — a mold so central that brewers rank it first among everything they do. No koji, no sake.
The soul of the process
Rice starch can’t ferment on its own. Koji is the answer — and the craft. Click through:
The brewers’ maxim ichi-koji, ni-moto, san-tsukuri — "first koji, second the starter, third the mash" — isn’t poetry, it’s priorities. Koji does the job malt does in beer, but grown grain-by-grain by hand in a hot, humid room over two sleepless days. It’s the step most responsible for sake’s existence and much of its flavor, and it sits at the center of the craft’s 2024 UNESCO recognition (Session 20).
Fix the hierarchy
Memorize the maxim
"Koji, starter, mash." If you remember one thing about how sake is made, make it that koji comes first.
Link to parallel fermentation
Note that koji’s gradual starch→sugar conversion is what lets the next session’s simultaneous fermentation run long, cool, and strong.
Questions
Flashcards
Lock it in
From memory:
- What is koji, and what does it do?
- What job does koji do that malt does in beer?
- What does "ichi-koji, ni-moto, san-tsukuri" mean?
- How does koji enable parallel fermentation?
- How does koji-making affect flavor?
The starter &
fermentation
Sake’s defining trick, and the reason it stands apart from every other drink: two conversions running at once, in one tank, to the highest alcohol nature allows.
Two reactions, one tank
This is the mechanism that makes sake sake. Click through:
Notice that fermentation temperature is a primary flavor control: cold and slow coaxes the fruity/floral ginjo-ka of a daiginjo; warmer and faster builds a richer, more robust sake. Combined with the polishing ratio from Session 5, temperature is one of the two biggest style dials a brewer turns — and it explains why the fragrant grades are also the fussiest and priciest to make.
See the uniqueness
Explain it in one line
"Koji turns starch to sugar while yeast turns sugar to alcohol, at the same time." That sentence is sake’s signature — the most complex fermentation in the drinks world.
Connect to fragrance
If your sake is fragrant and clean, thank a cold, slow ferment; if rich and robust, a warmer one.
Questions
Flashcards
Lock it in
From memory:
- What is the moto/shubo?
- Explain multiple parallel fermentation.
- Roughly how strong can sake get before dilution, and why is that notable?
- What does cold, slow fermentation produce?
- Why is the mash built in three stages?
Pressing, pasteurization
& water
The finishing steps — and the practical payoff of the whole production block: knowing why most sake wants to be drunk fresh and cool, and what the words nama and genshu are telling you.
From mash to bottle
Fermentation done, a few decisions shape what reaches you. Click through:
Here is the block’s practical lesson: most sake is meant to be drunk fresh — usually within a year, stored cool and dark — and unpasteurized namazake must be refrigerated and drunk young. Age is generally not a virtue (the deliberate exception is koshu, Session 12). This mirrors olive oil’s clock: a great sake mishandled or left too long is no longer great.
Check freshness & terms
Find the date & terms
On your bottle, look for a bottling date and for "nama"/"namazake" (keep cold) or "genshu" (undiluted, stronger).
Store it right
Move sake to a cool, dark place; refrigerate anything nama. Plan to drink open bottles within a few weeks and unopened ones within the year.
Questions
Flashcards
Lock it in
From memory:
- What does pressing (joso) separate?
- What is namazake, and how must it be kept?
- What does genshu mean?
- Should most sake be aged or drunk fresh?
- Why is finished sake usually diluted?