Freezing Yeast

[Andy Wandersee]

I'm just curious how long the yeast can be kept in the freezer before it is no longer viable. Thanks

 

[Firestix]

Can I use breast milk bags to store yeast? They are already sterile and rated to be frozen.

 

[Brewitt]

Sure. Breast mild bags should be great.

 

[David schaal]

Hi,
I have been reading and watching various methods for home freezing yeast. This looks great. I have a question.
The method and thread talks about sanitizing everything. Some times the word sterilize is used in the thread, but I get the idea that you are only sanitizing (e.g. you can't use Starsan to sterilize plastic components.
Other sites and videos have stressed that equipment should be sterilized (using a pressure cooker or autoclave if you are so lucky). Have you had any issues with infection with sanitizing versus sterilizing?
This method seems a whole lot easier than others I have seen.
Thanks!

 

[Bryan]

How did you come to the conclusion that 25ml of yeast slurry will have 40-50 Billion yeast cells? Shouldn't the density of cells in the slurry depend on how many cells were create in the starter? I usually build a 1.5L starter and with a fresh pack of 100 billion yeast cells, and with a SG of 1.036, the brewersfriend starter-calculator
(https://www.brewersfriend.com/yeast-pitch-rate-and-starter-calculator/) says that you can get up to 316 billion cells. I typically pour one liter of the starter with yeast in suspension into a 1L jar and crash for a few days prior to brew-day, and the other half-liter into a half-liter jar for future starters. If I did get the full potential of my starter, that .5L jar should contain 105 Billion yeast cells. I have measured the yeast cake in my .5L jar and it is exactly 25ml, so to me it seems odd that you say its half to sixty percent fewer cells than I reckoned. Is it that the missing cells are still in suspension at time of decanting? It seems unlikely that 50-60 billion yeast cells would refuse to settle out after a few days cold-crash.

 

[code3kid]

First of all, thank you very much for your time with this write up. I have only just recently found it. Quick question for anyone that has successfully used this method. What kind of viability have you found after thawing these yeast vials? In general, for example, if you were to purchase a pack of say White Labs liquid yeast form your local home-brew shop that was produced even just 1 month before you bought it, that 100 Billion cells is already down to approx 75 billion.
I'm sure that, even under the best of conditions, the little yeast cell walls are going through some tremendous stress in the freezing and thawing processes. I wouldn't be at all surprised by less than 50% viability after thawing, but who knows? Anyone's input on this is much appreciated.