Yeast starter culture

Sake is made using 2 microorganisms, koji (麹) and yeast (酵母). I described a little about koji in my last posts- the next step in brewing is to start a yeast culture (300-400 L) using koji-rice, water, rice, and of course, yeast. This is called the moto, and takes from 1-2 weeks to make depending on the grade sake being made. In our first batch of sake this year, we are making honjozo (本醸造) and will use a 1 week old moto. After mixing all the ingredients, the yeast start multiplying very quickly, so controlling the temperature is very important. After a couple of days, our moto was proceeding a little too quickly (consuming too much sugar) so we had to slow it down using a large aluminum container filled with ice.

Cooling down the yeast starter culture

The moto gives off a great smell, very fruity, with hints of bananas, and is very active.
In a few more days it is going to be ready, and we will use it to start the true fermentation for the first batch of sake, called soe shikomi (添仕込み), which requires the addition of more koji-rice, water, and regular rice.

Team photo

Today, we took the Tomono brewery group photo:

 

The Tomono brewing team

From right to left is Suda-san, Haruka-san (also a Tomono), Tomono-san (head brewer), me, and Iida-san.  We are a pretty young group of brewers compared to most  other sake breweries, with yours truly being the oldest member.

Tomorrow is a 6.30 am start, so it’s off to bed for me.

 

Making Koji- part 2

It is fitting to divide making koji into two parts, as the entire process takes about two days.
The first thing in the morning, 7.30am to be exact, we went to the muro to check on the sleeping koji mountain. Although the koji was not visible yet, the rice was giving off a distinct ‘koji-smell’ and the temperature had climbed up to about 36C. It was now time to break down the mound of koji, which had become somewhat hard due to the loss of water, into very small clumps and move it into cedar trays (koji-hako). This work must be done to quickly to avoid the temperature dropping too much, which results in unhappy and slow-growing koji. After moving the koji into the trays, they were again covered with blankets to retain the heat and moisture. As it is very important to monitor the temperature in case it needs to be adjusted, we inserted two remote thermometers into a couple of trays which send a single to the unit on the first floor of the kura. A very handy tool indeed, as it saves continually climbing the stairs to the muro to check the koji temp.

After another day of growth, this koji-rice will be ready, and we will use it to feed the 400 L yeast starter culture.  For those interested, here is a link to the blog of the sake brewery’s head brewer, and a picture of me in action: http://sawanohana.exblog.jp/.