Frozen Yeast Starters

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wee stu

wee stu's brury - hand made beers, award winning l
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...... or, the Mr Bean of homebrew does it again!

I'm new to these liquid yeasts, but I've used a couple and reserved some from the pre fermented starters in coke buddies for later use - stored in one of the fridges at 4c (ala the Grumpy's manual).

Anyway last Saturday I knew I was in for some good grace catch up time with Mrs wee stu, and had to spend hours of backbreaking toil in the garden to make up for a couple of brewday weekends.

Gardening is thirsty work, so I started by grabbing a carton of fluid repleneshment from a local source. (Safari Lager from Tanzania - chuggable stuff, excellent for fluid replenishment, and much the same price as West End or VB - at 5.5% ABV you need to drink a bit more for fluid replenishment, because you dehydrate quicker - but them's the breaks).

Only trouble with the local source is that the tinnies are warm. So I wacked them in the nearest available fridge, ramped it up to the coldest setting and got to work in the garden. End of gardening, I downed a few coldies, and felt a warm inner glow. Always nice to please the better half and indulge your passion for exotic beers at the same time.

Three days later, the garden looks a darn sight better, the Safaris are lip puckering cold ...... and the two coke bottle buddies of 1056 American and 1272 Scottish yeast starters, lurking at the back of this particular fridge, are frozen solid.

Serious question time. Are my yeasties going to be all right?

I've dropped the fridge back to the 4c setting, and my inclination is to let the yeasties settle back down in there. If they seem happy with that, I'll then use them in a fairly expendable brew (if such a thing exists). But I won't do this if you guys know better.

What happens to yeasties when they freeze?
I've "Heard" that freezing yeast causes the cell walls to burst,killing the poor little buggers. Then again I've also heard that people have found starters in the back of fridges in all sorts of condition and have been "Fine".

My advise would be to grab a couple of your favourite brew cans and booster bags. Make fresh starter wort and see if you can get them to take off again. Then pitch them into the can/bag mixtures.
gotta agree with linz wee stu.ramp them up and see what happens.kinda like my earlier post on whats a good yeast and a bad yeast after some long time storage.
im none the wiser on taste so i guess for your question if you have activity and they taste/smell all right(this is my tricky bit that i dont understand)then go for it.

please post back how it went then we will all be wiser for it.

big d

ps the only bad thing about this is you may have to sacrifice 23 litres of brew to the netherland if its no good.a very time consuming way to find out. :(
How do yeast "ranchers" freeze theirs and keep them viable?

wee stu, make a quick 1 litre starter and pitch one in (slowly ramp its temp up to room temp). If it ferments out, ramp it up to 2 litres and 3 litres and put on a brew if it smells OK.

My guess is the cold snap won;t have killed them all off. You should have enough viable cells to get a starter going. However, I've never frozen a starter myself.
"Ranchers" usually take a few strands of the yeast and put it into a glycol/glycerene base in a petrie dish/t-tube............I Think!?!
You will have had yeast cells die, but there will still be a good proportion of viable yeast cells. As the others have said, make starters with the thawed starters you have.
I will make a starter with the Scottish when I get home tonight - I've got back up Scottish slurry in another fridge if this doesn't take in time for the weekend's brew.
To properly store frozen yeast you need to store them in a glycerol solution. Same with bacteria and other cell types. It's the ice crystals forming inside the cell that end up rupturing the cell wall. You should still have some lively ones left but who knows how many. Proper frozen yeast cells need to be treated like this:

Freezing Yeast Cells

Grow up cells in medium at 30oC
Mix with .8ml cells with .8ml of YES (yeast essential media) containing 30% glycerol (autoclaved) in a cyrotube, such that the final concentration of glycerol is 15%
Store cultures at 70oC. Cells will remain viable for several years.

The glycerol helps to minimise the amount of ice formation in the solution and also prevents the increase in concentration of the remaining liquid (occurs when the water freezes leaving behind a more concentrated solution for salts/sugars etc.)

Quick overview anyway, but generally that's the way it works. A fair bit of messing round for the average punter though.

Is there any problems with yeast mutation caused from the freezing?
Well, it took a while longer than I'd intended. But, the good news is that the frozen Scottish yeasties (or at least some of them) seem to have survived the trauma of suspended animation and are back in business.

Racked up to a 2 litre starter, the previously frozen yeasties are currently causing noticeable airlock activity in a Grumpy's all extract Belhaven clone. :rolleyes: Home at last!

Sorry GMK, but given the trauma they had endured, I pitched the lot, I still have some other (not previously frozen) Scottish yeast slurry I can split and save if you want some.

wee stu
i definately want some if you can split it.
I was slow to get the starter going, the starter was slow to take, I took my time about doing the brew and pitching the starter, and it was a while before the airlock got going.
But, now, those once frozen Scottish yeasties are throwing one of the best krausen I've seen yet.
Halleluyah and the lord be praised!

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