Yeast Explores the Brewery

(9) Moromi (the Main Mash)

Yeast “Today it’s finally my turn! The kimoto yeast was finished a week ago, so I’ve had enough rest. I'm full of spirit and trembling with excitement!”
Koji “Take it easy now.”
Yeast “Who are you?”
Koji “I am Koji. Together with you, Yeast, I’ll do the fermentation today. Nice to meet you!”
Yeast “Let’s go for it!”
Koji “Don’t get too excited. Kimoto yeast like you has an oversupply of energy. If you are now so enthusiastic, it will be like racing a sports car through a narrow ally. Let’s keep cool.”
Yeast (puffing) “OK, I understand. Hmm, cool.”
Koji “That’s the right attitude. Look, the brewers have set up scores of wooden racks in the long, broad hall. On the racks they have spread out the steamed rice.”
Yeast “Why are they doing that?”
Koji “They are using the cold winter air to cool the steamed rice, so that it gets hard and will be more difficult to dissolve.”
- - On the first day, the first stage mashing (hatsuzoe) takes place in a small fermentation tank. Koji, water and steamed rice are added to the yeast. - -
Yeast “Why don’t they use a larger tank?”
Koji “If a small amount is put in a very large tank, it tends to cool down too soon. An ‘approach run’ has to be made for two days in a small tank.”
Yeast “I see, on the third day the mash is transferred to the large brewing tank for the phase called naka-jikomi.”
Koji “Yes, the volume is increased until about half of the large tank.”
- - After several days - -
Yeast “Today is the fourth day. The tank has been filled completely in the phase called tome-jikomi. It feels terribly tight!”
Koji “In the beginning, the moromi is very stiff because the steamed rice sucks up the water. That can’t be helped.”
Yeast “The brewers have speedily started stirring the mash with a large paddle.”
Koji “It’s important that they mix the stiff fluid well, without tiring.”
- - Several days later - -
Yeast “Hey, look. Foam of smooth bubbles has appeared on the surface. Next the angular ‘rock foam’ has appeared, too.”
Koji “Yes, indeed! Now high foam is steadily coming up.”
Yeast “It’s getting warm, so I feel great. The yeast is quickly multiplying.”
Koji “Keep your feelings in check! The crucial time is approaching!”
Yeast “Why is the moromi suddenly cooling down? The foam is also sinking.”
Koji “From now on every day the moromi will get cooler and the alcohol content will rise. The yeast will have difficulty breathing. This is the crucial time. While not very numerous, kimoto yeast like you is very strong. Don’t loose heart because of this low temperature!”
Yeast “The koji (I mean you), which does its best to provide me with nutrition, is also inside the tank. There’s no reason to feel down, let’s keep trying hard!”
Koji “Great, Yeast, you’re showing an astounding fermentation power! At such a low temperature that normal yeast would have died, you’re still continuing with the fermentation! Very impressive!”
Yeast “An elegant ginjo aroma is rising up from the moromi! The taste is also getting deeper and deeper.”
Koji “If the yeast dies, the bacterial cells dissolve in the moromi and damage the taste. You have to keep fermenting till the end...”
- - The master brewer comes and checks the taste - -
Brew master “The taste is delicious. Let’s start pressing!”
Yeast and Koji together “We made it!”