Novice yeast harvesting thread

[MTW]

A couple of questions, just to satisfy my own mind doing this...

Regarding stir plates causing stress: does shaking the yeast so vigorously not impart stress on the yeast in your method YW? Perhaps it doesn't matter at that stage...(?)

As well as keeping yeast in suspension, does a stir plate not also drive off CO2 and therefore keep a better environment for the yeast?

[Wonkydonkey]

The only thing I can add to this is,

by stirring there is a continuous gas exchange. Which is adequate for what we want.
Where A closed vessel, albeit a very large one, and that most peeps do not have access to. Soon Builds up with C02 as its a closed and less 02 for the yeast
I guess you like shaking your very large vessel. And maybe just one day, it may slip the cluches of your digits. As things have done in the past with my digits.
Where as those that stir, will be still stirring.

Things maybe disigned for one application. But very often they lend themselves to other tasks and do very adequate job of it.

You can't convince me that shaking is better and is more easy than stirring.
Ps, I have better things to shake, than shaking a bottle

[YeastWhisperer]

A couple of questions, just to satisfy my own mind doing this...

Regarding stir plates causing stress: does shaking the yeast so vigorously not impart stress on the yeast in your method YW? Perhaps it doesn't matter at that stage...(?)

I suspect that shaking does place an initial stress on the cells. However, I have shaken starters pre and post-inoculation with no quantifiable difference in outcome. I believe that the difference between shaking and stirring is that the cells are only exposed to physical stress for a minute or two versus hours or days.

With that said, one of the things that I noticed after switching to using a stir plate from my method was that my starters smelled foul. My beers also exhibited the signs of yeast stress-related off-flavors. That's what I drove me to question the stir plate argument. Starter media from a healthy culture does not smell foul.

As well as keeping yeast in suspension, does a stir plate not also drive off CO2 and therefore keep a better environment for the yeast?

A starter is saturated with CO2 during active fermentation whether it is stirred or not. On the other hand, the amount of O2 that is in solution at the beginning of fermentation does have a significant impact on fermentation. That's where my method shines. It is the lowest cost, lowest tech method that I have found to make a healthy high-performance starter. One does not need to shake if one injects O2 into one's starter wort before or after pitching.

[MTW]

Thanks. I will find the Shaken not Stirred thread again. It sounds like you've tested this a lot, whatever the exact science.

[windrider]

I had my first attempt at harvesting some yeast from the primary last night (WLP001). I left some beer behind after I racked it to my bottling bucket, swirled this around and put it in to a demi jar. I let it settle out for an hour. After the initial hour I couldn’t really see 3 distinct layers, just the top beer layer and the bottom layer. I went ahead and carefully poured part of the demi jar in to 2 x 500ml jars and put it in the fridge overnight. This morning I checked the jars and I’m still not seeing a clear yeast layer from the trub layer?

What do we think do I have any yeast in this jar as it all looks mixed up with the trub:

[Wonkydonkey]

My reply to this is, and it may not be everyone's view.

It looks like you swirled and swirled all the stuff in the bottom. Then you got what you have it the DJ.

all I do is swirle the last bit of beer to mix up the very top of the yeast cake. Ie the beer looks slightly milky to a bit muddy. Depending how muddy it looks will depend on what you need to do next

It may be a bit late, ie you have chucked the contents of the dj away. But if you have not then follow on...

Give the DJ a good mix up. Then leave it for no more than 10 mins. All or almost all the dead yeast cells will settle out. Pour off the liquid into a sterile container. This is your viable yeast still insupenders. (in suspention) if you put this container into the fridge and give it time to all settle out, then you will see the layers. You want the whitest/cream layer which should be on top or very near. It may be a lot or just a bit.

When you want to use this yeast, depending on how long it's been siting around in the fridge, you may or may not want to use the now very clear beer on top of the yeast in you brew, as it can taste horrid over time. If you feel the need to remove the beer from the top, decant it very carfully. And I f you've already made up some fresh wort from some DME so it's the right sg (1.040) and had it in the fridge as well ( so it same temp as the yeast that was saved) then add this DME to the yeast . And as before, give it a shake and let it come to room temp, to which it should start to ferment. If there was a lot of grey/brown matter it may have settled out but the yeast you want are happy in the new DME mix/starter. insuspenders again
There's many variables in this... Ie if you saved mostly yeast and are reusing soon etc. but it should get you a bit closer to where you want tobe.

I'm sure someone else will add a bit more

Hope this helps.

Edit, I just reread your post, i got a bit mixed up with jars and dj's
But yes there is good yeast there you still need to get it to settle out and get rid of all the other stuff. So like I said give it a shake, leave it no more than 10mins .......etc,

[YeastWhisperer]

What do we think do I have any yeast in this jar as it all looks mixed up with the trub:

The presence of off-white chunks in your crop tells me that you did not swirl the FV vigorously enough to break up and resuspend the flocs. One needs to swirl with a purpose when cropping flocculent yeast strains. Additionally, it also looks like you cropped everything from your FV. The trick is to take only the topmost 350ml of the liquid fraction after swirling and waiting a few minutes for heaviest solids to settle. There's a technique to cropping, but anyone can learn it.

If I were you, I would cap and shake both demijohns (i.e., the sediment should be completely smooth and mixed like a thin milkshake or a smoothie), wait a few minutes for the heaviest matter to settle, and then carefully decant the topmost 200ml from each demijohn. That 400ml should settle into around 175ml of thick slurry containing roughly 40% yeast solids. Two hundred milliliters of thick yeast slurry that contains 40% yeast solids will contain approximately 210 billion yeast cells, most of which should be viable. It does not matter if the cells and break settle into well-defined layers. In order for that to occur, one usually has to crop mostly the most (yeast layer on the bottom) or least (yeast layer on the top) flocculent yeast cells, neither of which are desirable. What matters is the consistency of the crop, which should contain no chunks. Chunks in a crop are a sign that the crop was not fully resuspended before decanting.

Two hundred and ten billion yeast cells is more than enough yeast to pitch 23L of wort. It gives one a pitching rate of 210 / 23 = 9.13 billion cells per liter. The maximum cell density for a liter of wort is approximately 200 billion cells, which means that the culture will have to double log(200 / 9.13) / log(2) = 4.45 times when pitched into a batch of wort. Remember, the yeast cell count grows exponentially at a rate of 2^n, where the symbol "^" denotes raised to the power of, and the variable n equals the elapsed time in minutes since the beginning of the exponential phase divided by the replication period (roughly 90 minutes); hence, it takes 90 x 4.45 / 60 = 6.7 hours for the culture to reach maximum cell density after the lag phase has been exited under ideal conditions, which means that the batch should show visible signs of fermentation in under 12 hours. The wort should go opaque with yeast cells in around 8 to 10 hours. Starting a batch below 18C degrees will lengthen the replication period slightly.