Rice · kōji · yeast
How sake is brewed: rice, kōji and parallel fermentation
Follow sake from polished rice through kōji making, a yeast starter and parallel fermentation. Learn why rice starch needs conversion before yeast can use it.
The short answer
Why is sake fermentation described as parallel?
Kōji enzymes make sugars available from rice starch while yeast ferments available sugars in the same main mash. Conversion and fermentation overlap instead of being completed as two entirely separate stages.
The transformation ledger
Follow what changes
-
Prepare rice
- Input
- Polished rice + water
- Change
- Washing, soaking and steaming prepare different rice portions.
- Result
- Prepared rice
-
Make kōji
- Input
- Steamed rice + kōji culture
- Change
- Enzymes capable of starch conversion develop.
- Result
- Kōji rice
-
Build starter
- Input
- Rice, kōji, water + yeast
- Change
- A healthy yeast population is established.
- Result
- Shubo
-
Ferment in parallel
- Input
- Rice + kōji + starter + water
- Change
- Starch conversion and fermentation proceed together.
- Result
- Sake mash
Words that carry meaning
Three terms to keep straight
- Kōji
- Cultured rice that supplies enzymes used in starch conversion.
- Shubo
- The yeast starter prepared before the main mash.
- Polishing ratio
- The percentage of the original rice grain remaining after milling.
Learn from evidence
Use these observation prompts
Separate conversion from fermentation
Kōji enzymes make sugar available; yeast then ferments available sugar.
Do not rank by one number
A lower polishing ratio describes more milling, not a universal guarantee of quality.
Scope and safety
This is a conceptual production map. It does not replace training, sanitation controls or a producer’s documented process.
Sources and further study
BrewMyBeer wrote the process map and observation prompts from the references below. They are educational summaries, not claims of hands-on production or tasting.