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Does Moto need Aeration?

Sake
#1

I started Moto (Sokujo/Shubo) phase last Thursday.
After 2 days the yeast started working, and it has been bubbling quite nicely for the last two days.
During Moto I understand it is wise to stir every 12 hours or so. Instead I’ve been shaking the 15 gallon vessel every 12 hours or so for a minute.

I can’t help to compare to making beer, since this is my only reference for brewing with yeast.
In preparing a beer-starter I use a stirring-plate and Erlenmeyer-flask. Besides that I aereate by shaking the Erlenmeyer every time I increase the starterwort (SG=1040).

I find myself very uncomfortable with three things in making this sake-starter Moto:

  1. Not using a stirring-plate, 2) Low temperatures. (50F as to 68F), I haven’t got a clue what original gravity I’ve started out with (for beer I prepare a welknown 1040/10 Brix starter).

Anyway, I just wonder if you guys do extra aerating or something else of your moto to give the yeast more stimulus for growth. . .

Another thing that crosses my mind is the possibility of administration of a drop of olive-oil in order to get the yeast in optimal condition. Any thoughts on that?

Greetings from the Netherlands!

#2

The problem with constantly aerating a moto, if there is one, lies in the difference between a moto and a yeast starter intended for beer. When you make a stirred starter for a batch of beer, what do you do with the starter wort after the yeast have finished fermenting it and settled out? You don’t add the entire volume to the destination wort, do you? Of course not, you taste it to check for unusual off flavors and then discard it. Right?

Not so with a moto. The entire volume of the moto is used to build up the moromi (if any is reserved, it’s usually used to seed the next moto). I’m not saying that constant aeration would damage a moto or the resulting batch of sake, what I’m trying to point out is that we could use some more data here. What would happen if you constantly aerate a moto? Possibly you could generate some funky off flavors. Or you could just have a really vigorous fermentation resulting from the higher yeast population.

I guess what I mean to say is: try it and let us know how it turns out. 8)

#3

Hello Jan,

First of all nice to see a newish face around here :slight_smile:

In a moto you are trying to end up with:

  1. A large thriving yeast population
  2. A ferment with just one living organism (yeast)

In order to have just one living organism we use yeasts capability to produce ethanol. A lot of organisms cannot tolerate even relatively small concentrations of ethanol and will die off within the first days of moto.

Yeast has two predominant metabolic pathways, where the flow through these pathways is largely dependant on oxygen availability (woaw I am geeky).

And now in english:

If no oxygen is available, yeast will predominantly produce ethanol.
If oxygen is available, yeast will do a mix of

  1. breaking down sugars with no concomitant production of ethanol
  2. breaking down sugars with a concomitant production of ethanol

Process (1) makes more energy for the yeast, but also requires oxygen.
Process (2) makes less energy for the yeast and does not require oxygen.

Also worth of noting is that oxygen is required for making of lipids important for the cell membranes.

So you want to have oxygen for making a large population of yeast that has healthy cell membranes, but you also want to have periods of no oxygen in order to make ethanol in order to kill off all contaminating organisms from the air, water and wherever they came from.

Therefore, the current process of only having some aeration makes good sense.

I hope this weren’t too confusing.

#4

Thanks Claes, your post has helped me understand things a little better, and so did the answer I got from Taylor. At the moment I’m inbetween first and second addition. For the recipe I sort of combine the instructions from your website (compliments for they are really transparent) and Taylor’s. Sofar I’ve not let temperatures rise above 10C (50F) and fermentation really takes off. I add the koji some 12 hours before the rice-addition and shook the fermenter like crazy to get some more oxigen in at the start of hatsuzu. These last things I picked up from Taylor’s recipe.

There is one thing besides the fermentationproces that really interests me, and that has to do with the filtering of the final product. I would really like to produce cristalclear sake. I suppose I should be satisfied with a reasonable tasting yellowish sake for a first time sake, but I like to stretch things a little. I read on the forum some members have experimented with using 1 micron filters besides bentonite.

But I suppose I should start another topic on this, which I will soon.

cheers,
J.J.

#5

hmmm, then again, I just might not.
Just read the thread: “filtering (decoloring) sake” and it sort of answers most questions.

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