# What's the big deal with freezing yeast?



## TSMill (16/1/15)

Hey guys,

I notice there is currently a lot of interest in storing yeast by frezzing it in a water/glycerine mixture. Not wanting to shit on anyone's parade, but just wondering why this approach is preferred over storing yeast in the fridge under water only?

Flicking through my copy of "Yeast", p 188 suggests yeast can be stored under sterile water for years without refrigeration. Technically I guess my water is not sterile (I boil the shit out of it), but that is somewhat balanced out by the fact my samples remain refrigerated. Table 6.5 suggests a maximum shelf life of 3-5 years, with a reliable shelf life of 6 months (which I guess is largely driven by your individaul yeast washing and sanitation regime). I've had no issues with yeast, either washed or split fresh from a smack pack stored in this manner, and I've regularly fermented with samples brought out of dormancy that are in the region of 18 months to 2 years old. 

The section on freezing (p.199) to me suggests there are many more factors impacting the viability of the end product, including how quickly the sample cools, glycerine to water ratio, temperature of the freezer etc. In addition, it notes that you should not re-freeze after a thaw, which leaves your entire library vulnerable to an extended power outage. 

Anyways, not trying to start any arguments, just would like to hear some of the percieved benefits of freezing over water storage.


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## Yob (16/1/15)

I plan to embed mine in ice 'trays' so will be somewhat insulated against extended power outages. Mine being in a deep freezer are pretty safe regardless.

Fridge samples I've noticed start to change colour after a month or so indicating mortality and or mutation. 

Freezing slows the metabolism to essentially stopped so samples remain more true.

I've also got a copy of the yeast book (naturally) and have read up on t he other types of storage, mineral oil etc but freezing seemed to be the best long term option.


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## mxd (16/1/15)

I'm just starting to freeze as yob's doing it


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## TSMill (16/1/15)

Yes I have noticed some colour change, moreso in the earlier samples I stored which I think had too much yeast in the vial (although I'm not sure why that would cause an issue). Other samples show a slight darkening, but I've not noted any perceptable flavour shift in the yeast profile. Even if there were a small degree of mutation in the fridge, surely this is no more than the mutation which would occur over the course of a ferment, or building up a sample prior to storage?


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## DJ_L3ThAL (16/1/15)

Ah so more water above is better than maximum yeast in the vial!? I'll inspect my yeast bank for colour differences of similar aged yeasts when I get home! Subscribed!


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## Yob (16/1/15)

DJ_L3ThAL said:


> Ah so more water above is better than maximum yeast in the vial!? I'll inspect my yeast bank for colour differences of similar aged yeasts when I get home! Subscribed!


actually, I believe less is better, even better still is to have a layer of mineral oil on the top as this stops any air contamination.


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## TSMill (16/1/15)

Meaning less yeast as opposed to less water I assume.


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## Yob (16/1/15)

Erm.. No? Less water.

I also forgot to add as to why, I've got +100 frozen vials I think, about 25 strains, I couldn't do that with jars of slurry


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## TSMill (16/1/15)

I don't store jars I've got the small screw top vials, probably 5-10% yeast and the rest water. 

I figure a certain mortality rate is expected, having a high water to cell ratio limits the concentration of dead cell crap that the remaining healthy cells are exposed to.


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## Yob (16/1/15)

But it's compact yeah?


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## MartinOC (16/1/15)

Healthy debate, healthy yeast.....


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## TSMill (16/1/15)

Yes, that is compacted.


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## Yob (16/1/15)

well.. as far as I remember, yeast dies pretty much from the top down.. regardless of the amount of water above them. Its the oxygen getting to them and them trying to do something to adapt to the environment,

another point to consider is that while not 'put to sleep' yeast will use up it's glycogen and thehalose reserves, then that runs out... bye bye..

Its another factor that got me into freezing rather than other forms of storage.


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## Camo6 (16/1/15)

I'm just getting into this yeast freezing caper both for the fun of it and to have a reliable source of yeast close at hand.

I used to farm yeast in test tubes with sterile water and found some were quite usable up to a year and a half in the fridge. This was pushing the limits though and didn't always lead to a successful ferment. I found some samples started to develop a rubbery vegemite smell (from autolysis I expect) after about a year or so and this made me look into better practices. Keen to see the results from freezing.

Speaking of which, pushed the BB to it's limits last week with an ESB using a 1.5l starter of 6 month old Wy1469. Was busier than a stomal therapist, refreshing the blow off bottle repeatedly but now have a healthy sample of top cropped West Yorkshire for freezing and repitching. What a yeast!


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## Yob (16/1/15)

:icon_drool2:

I know who I'll be hittin up for a vial then :icon_drunk:


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## Yob (16/1/15)

I do sincerely say laughing.. I too have pulled some pretty manky looking jars out of the fridge and made great beer from the yeast.. Rinsing and pitching...

-_- .... oh them were the days when I had* time* to nerd right out :lol: 

but as you say Camo, its fun as well


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## Camo6 (16/1/15)

Too true Jesse. 
I've not been brewing much the last 6 months and have realised how important proper labeling of yeast is. Got jars of god knows what in the fridge but can't bring myself to chuck em.


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## Yob (17/1/15)

Yeah baby, second sign of being a yeast hoarder


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## TSMill (27/1/15)

OK, so having a trawl through the yeast freezing thread, various other threads on other websites, and another read through of the yeast book and this is where I have landed:

Based on the experience of this site, evidence for the viability of freezing yeast maxes out at around 12 months. That is not to say that survivability is not longer, however there is just not the evidence to demonstrate it yet. I suspect that once frozen, yeast survivability will be longer than for other storage methods, but this has to be balanced against any mortality rates which occur during the initial freeze and the thaw (mortality rates unknown). 

In comparison, there is evidence that yeast stored under water is good for ~ 18 months, however most are not comfortable using it beyond this, as there is evidence of a high mortality rate, namely darkening of the yeast and in some cases a smell indicating some autolysis has occurred. A proportion of autolysed yeast should not be a problem if the stepped up quantity is significantly larger than the stored volume, provided some yeast survives. 

There is a suggestion that any yeast that is not completely dormant will be subjected to mutation over time. This may be a factor if you are only ever using first generation yeast from the packet, split into smaller quantities, however I am convinced that a greater rate of mutation will occur for any process that involves either washing yeast, or propagation on a stir plate, so for my processes mutation seems a moot point. 

So all of this really leaves me still sitting on the fence as to which is a better approach. Given both fridge and freezer space are ample, next time I am storing yeast I will freeze a couple of tubes and refrigerate a couple and will do a comparative test of viability after say 2 years and 5 years in storage. Stay tuned for an update in 2017.


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## Yob (27/1/15)

+5 years is the number I've read. 

With +25 strains now banked.. I certainly hope this is correct.. 

In saying that, there is a fair variation in the glycerine content in those, ranging from %15 to %50..

Only time will tell


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## Yob (27/1/15)

Not directly aimed at anyone but..

Seems to me that experimentation is to be encouraged, 'we' the freezers out there, are willing to put out Beer on the line.. And be consistent and accountable with our results... And not give up on it with procedural based failure.. And if you are unwilling to experiment yourself.. Sit back and wait.. ReResults are always pending.

My oldest stock is +12 months so side x sides are pending


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## Camo6 (27/1/15)

Camo6 said:


> I'm just getting into this yeast freezing caper both for the fun of it and to have a reliable source of yeast close at hand.
> 
> I used to farm yeast in test tubes with sterile water and found some were quite usable up to a year and a half in the fridge. This was pushing the limits though and didn't always lead to a successful ferment. I found some samples started to develop a rubbery vegemite smell (from autolysis I expect) after about a year or so and this made me look into better practices. Keen to see the results from freezing.
> 
> ...


A bit OT, just thought I'd share the pics from the brewbucket after transferring to keg. The bucket did pretty well to handle the krausen. A couple of times the blow off stuck and yeast got past the seal but once relieved it was airtight again.


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## indica86 (27/1/15)

TSMill said:


> In comparison, there is evidence that yeast stored under water is good for ~ 18 months,


What about yeast stored under beer - having a pH that is where you want it + ethanol to aid the preservation of the yeast?


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## Yob (27/1/15)

Remember that alcohol is toxic to yeast.


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## indica86 (28/1/15)

Yes but is yeast not more tolerant to ethanol than other nasties?


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## Yob (28/1/15)

Than water? No.


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## stux (28/1/15)

After having my yeast library wiped out by a baby induced 18month brewing hiatus I willibg to give freezing a try 

(Basically most of my wyeast splits are now 24-36 months old, and mostly look like peanut butter with oily/yellow liquid on top. Not comfortable bothering with)


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## barneey (28/1/15)

TSMill said:


> So all of this really leaves me still sitting on the fence as to which is a better approach. Given both fridge and freezer space are ample, next time I am storing yeast I will freeze a couple of tubes and refrigerate a couple and will do a comparative test of viability after say 2 years and 5 years in storage. Stay tuned for an update in 2017.



Yeasty Balls (I'll let others explain) have (been proven) survived for 4 years in the UK. I'm just about to carry out my first year test.


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## TSMill (28/1/15)

I'm going to look through my storage tonight, I think I will have some 1056 or 3068 in the order of 3 years old that I will attempt to revive.


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## DJ_L3ThAL (28/1/15)

I just revived some WLP300 thats 12 months old, harvested the slurry/trub, didnt even rinse or add water was under the beer etc which it settled below due to my own laziness.

Made an awful mess when it spilled out over side after 24 hrs from pitching!!! Photo was at 16 hrs from pitching.


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## TSMill (31/1/15)

Yob said:


> Not directly aimed at anyone but..
> 
> Seems to me that experimentation is to be encouraged, 'we' the freezers out there, are willing to put out Beer on the line.. And be consistent and accountable with our results... And not give up on it with procedural based failure.. And if you are unwilling to experiment yourself.. Sit back and wait.. ReResults are always pending.
> 
> My oldest stock is +12 months so side x sides are pending


Yep agree 100%, and the same applies to testing the limits of yeast under water. Just been through the archives in the bottom of the fridge and I've come up with the following guinea pigs, that I will start experimenting with once my stirplate becomes free again. 

*2.5 years old:*
Harvested from La Sirene Saison

*3 years:*
1768-PC English Special Bitter
2782-PC Staroprague

*4 years:*
3068 Weihenstephan
1056 American Ale

*4.5 years:*
3522 Ardennes
2308 Munich Lager

If I had to guess from a visual, I'd say the staroprague is the least likely survivor, followed by the Ardennes. 

I did a bit more reading on yeast mutation, and as per the linked PDF below, it seems to infer that the rate of mutation is a function of the number of times the yeast is recultured (it assumes this needs to occur once every 6 months). For example, 10% of brewing yeasts (300 strains tested) showed change in flocculation rate after 10 years storage (20 recultures). 

Linky:

http://www.pivarstvo.info/forum/files/yeast_propagation_and_maintenance_607.pdf


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## TSMill (9/12/15)

Reviving an old thread (and an old yeast)...

I finally got around to making a starter with my la sirene yeast vial, which is now 3.5 years old. Pitched 3 days ago into 200ml of wort and now stepped up to ~1 litre.


https://drive.google.com/open?id=0B1FswRQjGOu3RUYwR1BHeTh4M1U


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## Yob (9/12/15)

Was that under glycerine?


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## TSMill (9/12/15)

Nope, under water in the refrigerator.


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## DJ_L3ThAL (9/12/15)

TSMill said:


> Reviving an old thread (and an old yeast)...
> 
> I finally got around to making a starter with my la sirene yeast vial, which is now 3.5 years old. Pitched 3 days ago into 200ml of wort and now stepped up to ~1 litre.
> 
> ...


Sweet, I've still got the one you gave me, it's colour is much lighter than others and the ratio of slurry to water is quite low (heaps more water) than other vials with more slurry, less water which have gone a darker colour. Some are 'younger' than this yeast.

Perhaps there is a correlation between the water/yeast ratio that offers a far better long term protection?


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## Yob (9/12/15)

TSMill said:


> Nope, under water in the refrigerator.


the trouble (possibly) with under water (not distilled) is the ingress of oxygen and the potential for mutation, while it is still an effective short tern solution, freezing slows the metabolism to essentially stopped (at -20'c) so thereby keeping the original characteristics truer for longer (in theory)

All that said, we all know that in practice we all seem to get results that suit us with a great variation in practices and procedures, ultimately, if the system we adopt works for us, that's all that's important.

Good to see a healthy looking result, all you need now is a temperature controlled stirplate for them


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## TSMill (9/12/15)

Yes, the proof in the pudding will definitely be in the drinking!


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## klangers (9/12/15)

You guys should start selling your services to act as a yeast library!


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## TSMill (9/12/15)

DJ_L3ThAL said:


> Perhaps there is a correlation between the water/yeast ratio that offers a far better long term protection?


I think the yeast book talks about storing a match head sized sample in a vial, I have always tended to go a high water to yeast ratio as I figure this dilutes the effect of dead/ruptured cells, and therefore reduces overall mortality.

That said, I think some yeasts also just store better than others.


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## Weizguy (9/12/15)

> Yes, the proof in the pudding will definitely be in the drinking!


You have my attention, with both pudding AND drinking.
Please continue...


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## Killer Brew (9/12/15)

Happy to hear the yeast is alive and well. I had been wondering about the 2 samples being kept in my fridge for the last few months and whether I needed to hurry up and use them, sounds like they will be fine. Also about to use a new Wyeast 1217 West Coast IPA which I will also crop as it isn't always available.


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