Accidentally froze yeast

[kudos1uk]

I put two smack packs of Wyeast (Ringwood) in the back of the fridge a week ago, I used the first one yesterday and all was good, it activated and the FV is nice and lively today.

Last night I went back to the fridge to check the maximum recommended fermenting temperature on the unopened pack and realised I had Accidentally frozen the yeast where it was touching the back of the fridge, it was not completely frozen, maybe 50%, it could possible even have been the rupture pack that was frozen as there was a big area of ice.

It does have "Do not Freeze" printed on the pack.

The one I used was right next to the frozen one so must have been close to frozen, but obviously protected slightly from the direct cold.

Do you think it will still be viable or should I bin it?
I guess the simple answer is get a spare and if it does not activate, bin it and use the spare.
Just wondering if anyone has done the same and found the yest was OK?

 

[MyQul]

Freezing will definitely have killed off some or all of the yeast. If you want to test if any cells are still alive just put it in a starter.

 

[strange-steve]

It certainly won't have done it any good, but chuck it in a starter and you'll know if it's still viable. I suspect that if the whole thing wasn't frozen then there'll still be viable cells in there.

 

[kudos1uk]

Freezing will definitely have killed off some or all of the yeast. If you want to test if any cells are still alive just put it in a starter.

It certainly won't have done it any good, but chuck it in a starter and you'll know if it's still viable. I suspect that if the whole thing wasn't frozen then there'll still be viable cells in there.

Thanks guys, that's good advice, I didn't consider using a starter with a smack pack.

 

[strange-steve]

Thanks guys, that's good advice, I didn't consider using a starter with a smack pack.

Smack packs are not meant to replace a starter. A starter is used to increase cell count whereas the nutrient pack in a smack pack is only to get the yeast active.

 

[Chris17]

I've had a similar issue to this, except it was my starter that I accidentally partially froze. Hoping one of you guys might be able to give me a bit of advice?!

I made a starter last weekend with a pouch of Wyeast 1028 ready to brew an imperial stout today (plenty of cells needed!) I went to get the starter out the fridge after cold crashing this morning and the top 50% was a semi frozen slush. Luckily I have bought a couple of packets of Mangrove Jacks M42 as back up, because the starter itself took 3/4 days to actually start fermenting, so I was worried about the yeast in the first place!

Anyway my plan at the moment is to pitch the yeast from the semi-frozen starter and then if its struggling at all in a week or two I can just pitch the Mangrove Jacks dried yeast. Just wondered what the thoughts on this were? Would there be any downsides to pitching the dodgy starter yeast?

 

[Sadfield]

Freezing will definitely have killed off some or all of the yeast. If you want to test if any cells are still alive just put it in a starter.

Will it though? It would be interesting to see how hardy they are. Freezing isn't a massive drop from fridge temperature, yeast banks freeze yeasts to rediculously low temperatures and wild yeast survive frosts.

 

[The-Engineer-That-Brews]

Freezing isn't a massive drop from fridge temperature

It's not the temperature change that's the problem: it's the growth of ice crystals that damage the cell walls

 

[The-Engineer-That-Brews]

However, panic not: I use freezing to keep backup yeast cultures for sourdough; and I can say that while freezing definitely degrades the liveliness, yeast is pretty darn hard to kill, especially once it's in its 'survival' state (sporified). I would suggest, as others have said, making a starter culture with it as soon as possible after bringing it out of a frozen condition though

 

[Sadfield]

It's not the temperature change that's the problem: it's the growth of ice crystals that damage the cell walls

Sure that may be the mechanism of damage, I'm questioning how hardy yeast are to that, whether they have already adapted in preparation for that eventuality.

Yeast Adapt to Near-Freezing Temperatures by STRE/Msn2,4-Dependent Induction of Trehalose Synthesis and Certain Molecular Chaperones.

 

[The-Engineer-That-Brews]

You only need a few viable yeast cells to rebuild the population very fast once conditions improve - exponential growth is an amazing thing. Nonetheless the key is to reduce competition from other wee beasties during the early stages of that growth, which is why a sterile starter culture is probably a better idea than pitching straight into a brew.

 

[Joust]

I've always doubted how destructive it is.

I freeze pizza dough all the time and it's fine.

Even if I am comparing apples and oranges

 

[Brewnaldo]

Just accidentally froze a Wyeast Belgian High gravity. Ffs.

Having searched and found this thread I will lob it into a starter and see how that goes.

 

[Joust]

Just accidentally froze a Wyeast Belgian High gravity. Ffs.

Having searched and found this thread I will lob it into a starter and see how that goes.

Looking forward to your findings

 

[Brewnaldo]

Looking forward to your findings

I have taken it out the fridge and will activate it once it comes to room temp. I dont have a large enough vessel to do 2l starters so my plan is, put it in a 1 l starter, and if it takes off, let it ferment out, pour off and put it in another 1 l starter. And hopefully brew with it on Wednesday or Thursday. Updates to follow.

 

[Brewnaldo]

Ok, this yeast seems destined for me to kill it off, I have activated the smack pack, but found I only had 50g of DME. I topped it up to 100g with sugar and made the solution, but have since read this may now be a good idea.

I have ordered some LME for delivery tomorrow, so should I pitch it into this half and half mix, or wait till tomorrow and risk the yeast getting further ****** off at having nothing to eat for 24 hours?

 

[Brewnaldo]

@Joust

Further updates will follow but having thawed it out and activated the nutrient pack, the pouch was inflated like a balloon within a couple of hours, so the yeast is undoubtedly alive. I elected to pitch it into the half malt, half sugar wort. I will probably go for another starter after this one settles out but so far so good.

 

[Joust]

@Joust

Further updates will follow but having thawed it out and activated the nutrient pack, the pouch was inflated like a balloon within a couple of hours, so the yeast is undoubtedly alive. I elected to pitch it into the half malt, half sugar wort. I will probably go for another starter after this one settles out but so far so good.

Good stuff.

I knew you could freeze it.

Homebrewing seems full of myths and nonsense.

 

[Northern_Brewer]

I knew you could freeze it.

Homebrewing seems full of myths and nonsense.

You can freeze yeast - but it's no myth that you get significant losses in viability.

For instance Park et al 1997 tested wild-type yeast (CY4) which are probably tougher than brewery yeast and found that 2 hours of freezing caused early-exponential yeast to lose ~94% of viability and late-exponential yeast to lose 40% of viability. The typical commercial pack of yeast is more like the second than the first, but that's still a big loss - and the drop is proportional to the time spent frozen, after 6 hours the 40% drop goes to >75% loss of viability.

Freezing isn't a massive drop from fridge temperature, yeast banks freeze yeasts to rediculously low temperatures

As mentioned above, the introduction of ice crystals is the killer. If you're preparing cells for a yeast bank then a) you mix them with something like glycerol to protect them and b) you do the initial freeze by dropping them in liquid nitrogen to minimise the formation of ice crystals in the same way that Heston Blumenthal makes ice cream with liquid nitrogen to make it super-smooth, because it lacks ice crystals. Glycerol + liquid nitrogen is a long way from "just bung it in the freezer".

 

[Brewnaldo]

Good stuff.

I knew you could freeze it.

Homebrewing seems full of myths and nonsense.

The starter went off really well too, but I will definitely decant and do it agin with LME just to be sure as it will be going into a a Dubbel so reasonably high OG