Maintaining A Healthy Yeast Bank Long Term

[fearwig]

I've never had a problem with very old pitches of estery strains as long as I build up an appropriate starter. I just did a WLP-550 from over a year ago and it's tasting great so far (in the fermenter anyway). I might be more inclined to fret over an American style strain that old, where stress flavors are something to fret over.

 

[yeehaaa]

What is your opinion of top cropping to collect yeast?

 

[Michael Kelly]

I have been reusing yeast for a couple of years. I use a simple bleach solution on jars, counter, general area I'm working in (galley kitchen). I have had no problem. Beer is great. I have also reused yeast many times. I will let the yeast stay in the primary for a few days under remaining beer, then, wash the yeast before storing in fridge. I also save bleach solution for reuse.

 

[PoppinCaps]

Top cropping is a great way to collect a selection of highly active yeast. Collecting from the bottom after fermentation essentially gets you the same result, but cropping ensures an active population.

 

[Baza]

could you combine methods 1 and 3 by adding glycerin to pitch-able quantity of slurry then you could skip making a starter? would the freeze/thaw be too slow? too much glycerin going in the beer?

 

[Baza]

is there a way to test yeast slurry for bacteria levels. Can you grow a sample of slurry to see what else aside from yeast is in it? or can you see bacteria through a microscope.

 

[yeehaaa]

Thanks! Great article, by the way.

 

[TrickyDick]

Awesome write up again!
Thanks for the earlier response, and detailed follow up regarding cell counts.
I typically brew ten gallon batches of various OG. Was curious about the aforementioned density you a finding in your starters, if it would benefit me to do a larger sized starter, 2L instead of the suggested 1L in this case for ten gallons of beer.
Also, regarding sterilizing the tubes you are using. Can these tolerate being sterilized in a pressure cooker? An Autoclave (I have access to one at work)?
Do they come with those cardboard holders when you purchase the tubes?
TD

 

[wstehling]

Thanks for this great article. I have received my test tubes, rack and pressure cooker to go the frozen route, however I have a question. When you sterilize your water/glycerin solution in the pressure cooker, is the solution in a mason jar with the lid sealed tight, as if you were canning preserves or jam? Can you enlighten me on this aspect?
Thanks!!

 

[ortibauy]

Pete thank you for your post, so far I've been using
slants for my small bank and wanted to try frozen stock
with a White Labs (WLP002) which is very flocculant.
In steps 2. and 3. the decanted yeast was very clumped
and it was impossible to divide the decanted yeast into
the tubes 5 ml each.
What can I do to 'unflocculate' this decanted yeast into
a more liquid mixture?
Thanks!

 

[danthebugman]

I just did some tubes this afternoon with Wyeast 1098 and it's very flocculant also. I left the stir bar in and, after decanting, I put it on the stir plate while I was getting everything else set up. Seemed to work pretty well, but was still a little clumpy.

 

[danthebugman]

Don't seal it tight. You want there to be enough wiggle in the lid to let pressure escape or else...boom. I bought some autoclavable media bottles with screw on caps a while back and love them. I use them for making wort agar media and more recently for glycerin solution. If you're using a Mason jar, I would probably just put some foil over the top when sterilizing in the pressure cooker. If you're making a big batch and aren't going to use it all, I would Starsan a lid and ring and then put that on after you're done using it.

 

[ortibauy]

Good idea, I'll try, thank you!

 

[Keith Hartley]

Hi
Great article. Doing my 1st batch today.
What pressure do you can the glycerin/ water mixture?

 

[Keith Hartley]

The test tubes say sterile but do you sanitize them with stars an each time?

 

[TrickyDick]

For danthebugman. Link for those media bottles please?
For OP, poppincaps. When you refer to a "fresh yeast culture" which we begin with, I am wondering how I might translate that into using wyeast/white labs liquid yeast or dry yeast sachets when brewing.
For liquid yeast, I would typically make a 2 L starter with two smack packs or two vials (sometimes three or more vials, step up starters, or larger volume starters depending on what I'm brewing). What might we do when making a starter to collect a bit of the culture for a subsequent 1 L starter in order to generate ten vials for storage?
With dry yeast I do not make a starter. I do rehydrate in 10x the weight (or mass actually) in sterile water of the yeast. Seems to be the best spot for harvesting the yeast for storage, or stealing a portion for making a starter to collect enough yeast for ten vials for storage. What do you recommend in this situation?
I assume that in both instances, that it is better to use the fresh from commercial producer cultures to follow your method, rather then collect yeast from a finished batch of beer and attempt the same.
Thanks!

 

[Keith Hartley]

Did anyone else get way more yeast than expected? Ended up making a 1200ml starter instead of 1000, yeast was on stir plate for 48 hrs. I got 30 tubes of yeast & probably dumped another 100 ml of yeast down the drain. I crashed & dumped off the stale beer twice before filling the tubes. Could of stored some yeast in jar for another brew.
Can these tubes be cleaned, sanitized & reused?

 

[Keith Hartley]

Do you reuse the isopropyl alcohol?

 

[Staylow]

Great article. I got my frozen bank underway a few weeks ago with four strains in the freezer as of now, with two more strains cold crashing.
Question - is there any reason why I shouldn't use my glycerin solution at a later date, after it's been pressure cooked, opened and used once? As long as the jar is closed back up when done, it should be fine, correct?

 

[PoppinCaps]

~15psi

 

[PoppinCaps]

Nope, they're single use as far as I'm concerned. Cheap enough. But you could reuse them using a caustic, acid, starsan treatment. If you put a different yeast strain in there, the extra effort would help against contamination. They can't be autoclaved.

 

[PoppinCaps]

Yeah, as long as the final glycerin concentration is around 12.5% it would work just fine to freeze as normal. However, you would also be storing any bacteria or wild yeast present in the slurry from brewing, so it may defeat the purpose of a frozen pure stock.

 

[PoppinCaps]

You can see bacteria through a scope, though you would usually need a good 40x objective. The cheapest way to test for viable bacteria is to do serial dilutions of the sample, and plate a low volume out on agar. Grow the plate for a few days and count bacteria/yeast colonies. There's no cheap kit that I know of that will tell you any better.

 

[PoppinCaps]

The tubes come with a holder typically, and none can be autoclaved that I've seen. You could get glass vials and autoclave those and reuse them.
Yeah, going up to 2L for a 10 gal batch makes good sense. As long as you're getting enough cell density.

 

[PoppinCaps]

As far as slurry volume, it should be noted that I have seen some strains take up almost twice the volume of another strain with the same compacted total number of cells, PacMan is a good example, they're pretty plump cells.
You can clean the tubes, and sanitize by chemical, but they're not autoclavable.

 

[PoppinCaps]

Yep

 

[PoppinCaps]

Yeah, that's what I do, just open it up for as little time as possible and seal when you're done.

 

[Keith Hartley]

Thanks for the responses.
Want to make sure I understand this.
Do you think the 30 tubes of yeast are going to be alright or too weak? I guess a starter will be the test. Do you usually just fill the ten tubes & dump the rest?
Thanks again

 

[ajr628]

Great article. Definitely helps me get my head wrapped around storing yeast properly. Gave the courage to take the the step deeper into frozen stocks.

 

[Baza]

I've just put first lot of yeast in the freezer. if the yeast was stored at -17 rather than - 20 C how much do you think this would reduce storage time. does freezing have a significant effect on viability. if you frozen 20 billion cells how many would you expect to survive defrosting after 6 months in the freezer? thanks