Let's Freeze Some Yeast

[Bribie G]

I recently started a Slanting thread as that's what I was intending to do, and got some great advice. However during the course of things, the alternative - freezing tubes of yeast - was presented so I had a good think about it and:

I have an old school freezer that needs de-icing every couple of months so the yeast tubes can be in deep freeze with no interruption as can happen with modern no frost cycling freezers. I acquired some kit and a bottle of glycerine (to prevent cell walls bursting which is the major no no in yeast freezing). I'll certainly revisit slanting if I get bad results down the track. Also please note I don't have a pressure cooker yet: relying on steaming only.
So here goes:

8 test tubes (30ml) to be prepared for freezing. I'm following the method provided by this site:

Into the stockpot:
8 test tubes and caps sitting in a Pyrex bowl,
a few assorted new syringes from the chemist sitting in a couple of Pyrex 250 ml teacups.

We are looking to get a cup containing 120ml of 70% water / 30% glycerine, and a cup of 120ml yeast slurry to fill 8 tubes.

Steam for an hour.

Arrange a work area away from any spores and yeast as might lurk in your brewery. Using a small graduated syringe, put 85 ml of boiled kettle water and 35 ml glycerine into one of the glass cups or your equivalent bit of kit, and microwave to a boil. The into each test tube, syringe 15 ml of solution, cap the tubes and cool rapidly.

Obtain a cup of slurry / yeast from a starter / topcrop from Yorkshire yeast etc etc.

Into each test tube, syringe 15 ml of yeasty solution. Cap, label and freeze.

Apparently if you fridge them for 24 hours and then freeze them you get better viability.


I look forward to the results. BTW the yeast is Wyeast 1968 London ESB. B)

 

[Rodolphe01]

Between all your experiments, do you get time to make beer that you will actually drink ??

I'll be watching this one with interest.

 

[RdeVjun]

Thanks Bribie for the great guide! B)

There are other uses for those gloves after all!

 

[rotten]

Thanks Bribieg.
Apart from actually just storing yeast cake or top cropping, that's the easiest and most uncomplicated explanation I have seen.
Cheers

 

[Cocko]

Legend.

:icon_cheers:

 

[Eater]

Immaculate
Look forward to seeing results

 

[Adam Howard]

What's involved once you thaw out the yeast to separate it from the glycerine Bribie?

 

[white.grant]

Hi Bribie

That's a good way of storing slurry for a longer period of time, though I don't think you should look to it as an alternative to slanting .

The whole idea behind slanting is that you are using a fresh sample of yeast straight from the package and growing colonies in a controlled way so that they will not mutate.

With a slant you can continue to re-culture and maintain the viability of your bank, but your slurry samples will have already mutated.

cheers

grant

 

[brettprevans]

Interesting bribie. I remember Spillsmostofit freezing yeast years ago, I wonder what his method/results.

Freezing would be a good option to prevent yeast going off, just depends on how it affects it's viability

 

[beerdrinkingbob]

Hey Bribie,

Just a quick question to make sure i have it right, you rapid cool the mix say in the freezer till it goes solid?? and then add the yeast slurry.


Thanks again, great work much appreciated :super:

 

[np1962]

Hey Bribie,

Just a quick question to make sure i have it right, you rapid cool the mix say in the freezer till it goes solid?? and then add the yeast slurry.


Thanks again, great work much appreciated :super:

bob,
The idea is that the yeast combines/is surrounded by the glycerine solution which never quite freezes solid thereby holding the yeast in very low temperature conditions without doing damage to the cell walls.
Nige

 

[schooey]

Hi Bribie

That's a good way of storing slurry for a longer period of time, though I don't think you should look to it as an alternative to slanting .

The whole idea behind slanting is that you are using a fresh sample of yeast straight from the package and growing colonies in a controlled way so that they will not mutate.

With a slant you can continue to re-culture and maintain the viability of your bank, but your slurry samples will have already mutated.

cheers

grant

Great way to split a fresh smack pack into five and keep for an extended period though...

 

[MeLoveBeer]

Great work Bribie. Any chance of documenting the usage half of the process? Does the whole lot get pitched into your starter after being defrosted? (I can't imagine that the glycerine can be decanted)

 

[Nevalicious]

Me love beer

Follow this link

Post 7??

Bribie, I just did this last night too. Although I just used a smack pack, divided up into 4 glass 20ml vials with approx 5ml of glycerine in each, poured the remaining into a 700ml starter, and had it on my stir plate all night. Went right off!! :beerbang: Much like Schooey suggests above...

This may be a little dumb, but I checked my frozen samples this morning. Yes I know that they have been in the freezer, but they are rock solid. I thought the glycerine would keep them somewhat not frozen?? Anywho, time will tell when I go to step up from one of the samples. It'll either work or it wont hey!?

When I use the starter in my next brew (this weekend) I might try my hand at top cropping. I have read Wyeast 1007 loves a good top cropping, and freeze some more.

Nothing like making your dollar go further.

Tyler

 

[BjornJ]

Great job documenting how to do it, thanks BribieG.

I store yeast in test tubes with sterile water over for months and years in the fridge, but this is probably a better way, eh.
And it doesn't look all that hard.

Hmm maybe something to try at some point.


If the vials freeze solid, did that mean the yeast is now dead and next time use more glycerin?

Bjorn

 

[white.grant]

Great way to split a fresh smack pack into five and keep for an extended period though...

Perhaps, I guess it all depends on how viable the yeast are once they thaw.

cheers

grant

 

[Bribie G]

I think the idea is that they do indeed freeze but the glycerine has stopped the cell walls from bursting, like freezing embryos etc. Should work ok with smackpacks - 125ml (if that's what is actually in a smack pack) should give 8 tubes as well, but would need a lot of culturing up afterwards compared to a whole smack pack. From what I've read the most popular method with a smack pack is to do a healthy starter to increase the yeast population, use the starter to do your tubes but have enough left over to pitch a brew in the normal manner. So with subsequent brews you are culturing up the same material that was in the original starter.

Starting up and stepping up would be similar to slants but hopefully a bit quicker as it's a bigger yeast sample. Glycerine is quite edible and I guess the small amount that ends up in a brew would be negligible, but I would probably run up a starter to the point where there was a fair amount of yeast on the bottom, and pour off the upper liquid layer and then keep stepping up the starter with fresh wort until ready to pitch, would get rid of most of the glycerine.

Edit: last year I was clearing out the freezer to defrost it and there was a Wyeast (forget which) - had been sitting there for two months at least. It cultured up ok, although somewhat slower than usual. I reckon with the glycerine treatment it should work fine.

 

[unrealeous]

Nice work BribieG - but I'd suggest one slight change to your process for next time. That is - fill your containers with 85mls of glycerine, do the lid up tight and then pressure cook them. Once they are cooled - when you go to put the yeast slurry in - you only want the lids off for as short a time as possible. I say this since I used to do quite a bit of mushroom cultivation on agar slants - and anything uncovered for more than the shortest time would often end up with a rouge bacteria - and I see in your photos all the vials sitting there with the lids off after sterilization.

Anyway - good effort - love the photos - keen to see how well it works.

 

[MeLoveBeer]

Me love beer

Follow this link

Post 7??

Cheers Nevalicious. Have been splitting wyeast packs for a bit (just storing test tubes in the fridge) and am very interested in this as a long term storage solution.

 

[argon]

Great stuff Bribie, good simple guide to help everyone out. I'l be giving this a go shortly to keep my PC slants, as soon as i can source some tubes.

Cheers
:icon_cheers: