The story - Wine and sake are alcoholic beverages both made through the process of fermentation  

The raw material for sake is rice.

“Rice is a starch”→ “It saccharifies with the action of koji and converts to glucose liquid.”

    Glucose (gasoline) + yeast (engine) → generates alcohol. (fermentation)

    Parallel double fermentation (saccharification and fermentation occurs in parallel)


 The raw material for wine is grapes.

    Glucose (gasoline) + yeast (engine) → generates alcohol. (fermentation)

    Single fermentation (no need for saccharification)


<Point>

There is a basic principle that yeast consumes only glucose. By consuming glucose, it generates alcohol. It consumes nothing but glucose.

Humans are the same. We convert food into glucose in our bodies to generate energy.

 


 






The raw material for sake is rice, and that for wine is grapes.
Alcohol is generated by yeast consuming glucose.
If I clarify more, yeast consumes glucose only.
So in the case of wine, fermentation starts only by mixing wine juice and yeast together.

                           (The photo on the right is the rice)




But in case of sake, the raw material is rice, which means starch.
Yeast does not eat starch itself.
For the yeast to eat starch, the starch must be converted into glucose with the help of koji.

 Let me explain what “koji” is.
“Koji” is a mold that grows on steamed rice by sprinkling koji fungus on it.
The propagated fungus is a clot of enzymes, and these enzymes act to convert the starch into glucose.
  
                             (The photo on the right is Koji)
   

  Note: Starch means that of steamed rice. Enzymes work better by steaming rice. This is why rice used for making sake is steamed.
       In ancient times, food was always steamed before eaten. People started to boil rice only after leak-proof vessels were invented.

If what I have explained so far is clear to you, let me go back to the title, “Both sake and wine are brewed alcoholic beverages”.
I would like you to remember the idea of the car. Any excellent car wouldn’t run without gasoline. It wouldn’t reach its destination.
The same is true for fermented alcohol. Any excellent yeast (engine) wouldn’t get to a wonderful destination without glucose (gasoline).

A car stops when it runs out of gasoline. It won’t be able to get to a wonderful destination.

So wine brewers work hard to grow grapes to get to wonderful destinations.
In the case of sake, it is the koji that makes the gasoline.
So we work hard to make koji.

Whether it is possible to get to the final destination (the flavour that we imagine)
will depend on the performance of the koji that has been made.
(The quantity and quality of gasoline generated differs according to how the koji is made)




This is the mechanism of how fermented sake is made. I hope it is all clear to you.