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Dormant Yeast or Epic Failure

Newb question here. I have been homebrewing for several years and stumbled upon Bob Taylor’s Website and decided to try making sake. I doubled his recipe (total of 20 lb rice) and followed everything else to the letter. My rice and koji were sourced from FH Steinbarts who gets their sake supplies from a local sake brewery. My yeast was 2 packs of Wyeast Sake Yeast.

Here is the problem. Everything seemed to be going well until the final addition of rice (10lb). After I added the rice I held the temp at 70* overnight and fermentation was VERY active by the morning. I then transferred it to a temperature controlled freezer (50*) for 3 weeks. I removed the vessel tonight and it hardly appears that any rice has broken down. There is approximately a 3-4 layer of clear fluid (in a 12 gallon fermentation barrel) and the rest of the fermenter is full of rice that appears not to be breaking down. I tried to get a hydrometer reading but there isn’t enough fluid to float the hydrometer.

Did the yeast go dormant or was the last addition of koji bad or did I just screw up.

I tried the search function, but I was having a hard time finding a similar topic.

Thanks in advance for any help or advice.

You really need to do one of two things, Bob:

1 - Take a hydrometer reading.

2 - Taste your sake.

If the specific gravity is significantly above 1.000, or the flavor is very sweet, then you know you’ve got a problem with your yeast. If the flavor is not noticeably sweet and the SG is at or below 1.000, but you can’t detect much alcohol, then you’ve probably got a problem with your koji.

Most likely, however, everything is fine. You’re going to have a noticeable amount of what looks like rice in your moromi at the end of 20 days of fermentation. That’s why the joso step is necessary: to separate your liquid nigorizake from the solid lees.

Oh my…mea culpa and pass the humble pie. I managed to get a specific gravity of 0.9900 at 67* and the taste of the sake was alcoholic, but not sweet. I was shocked at how much sake I was able to squeeze out of the solids. I ended up with about 7 gallons of sake.

Thanks so much for the advice Bob and putting up with the basic questions.

One final question; would dropping the temperature down to 34* (lagering temperature) for the next 2 weeks be of any use to help clarification before using bentonite? This is still the homebrewer in me trying to assimilate sake technique.

Thanks again!

If your temperature controller is anything like mine, you probably have a 2º differential. That makes 34º a little low. I usually drop mine down to 36º for a couple weeks to halt fermentation and coax the yeast into settling out before racking, adding bentonite, and proceeding with the first pasteurization step.

Pardon my ignorance, but this is referring to 36C, correct?

Sorry, no. Being American, Drbobcat and I are both referring to temperature in degrees Fahrenheit. For you, that would be more like 2ºC.

Oh haha I live in Arkansas :expressionless: I use an STC-1000 based controller and it only displays in C.

36F is freaking cold! How does this aid in settling? It would seem (to inexperienced eyes) that a higher density fluid would actually hinder settling. Forgive the ignorance; I am just finishing the Hatsuzoe stage of my first brew.

Well, you’ve put your finger on exactly why the subject is and should be open for debate. Personally, I cold crash my sake for three reasons:


  • [b]Yeast metabolism[/b] - I want to stop my sake fermentation at a target specific gravity. Shutting down the yeast with cold is a lot easier for me than having to go back and ameliorate the sake with rice, sugar, or koji. [/*]
  • [b]Enzymatic activity[/b] - I want slow down or halt the activity of protease enzymes in the moromi. Protease creates amino acids by breaking down proteins, and amino acids contribute to a darker color and harsh flavor in the finished sake. [/*]
  • [b]Flocculation[/b] - Sake yeast isn't known for being very flocculant, but I was to encourage any suspended and active yeast to settle out as much as possible. Shock the yeast into dormancy with cold and let gravity do the rest.[/*]
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