Yeast Viability

[TerritoryBrew]

Just went looking through my freezer where I keep all the hops and came across some Nottingham Yeast with the use by date of November 2008. This is the vacuum sealed variety and available from one of our sponsors. My question is, would the yeast still be viable if it had been kept in the freezer for so long? And what, if any, off characteristics would this yeast exhibit if it were to fire up.

Cheers,

TB

 

[Dazza_devil]

I'd use it for yeast nutrients.

 

[Screwtop]

Just went looking through my freezer where I keep all the hops and came across some Nottingham Yeast with the use by date of November 2008. This is the vacuum sealed variety and available from one of our sponsors. My question is, would the yeast still be viable if it had been kept in the freezer for so long? And what, if any, off characteristics would this yeast exhibit if it were to fire up.

Cheers,

TB

You too

Have been using mine at 1.5 times the normal rate without problems. Not something I would recommend as I have no idea of how yours has been stored during this time, some freezers (frost free) defrost periodically. It just so happens I have part of a block that has been kept in the freezer in a ziplock bag and only removed for weighing out the required amount, been doing this for nearly three years. A double batch of Bitter has just finished at 1.009 from 1.037 an attenuation of 74% for a mash temp of 68C. A great yeast Notto

Cheers,

Screwy

 

[Nick JD]

A recently made a great Ale from a pack of S04 that was from march 2007 ... frozen the whole time.

Make a starter?

 

[RdeVjun]

Pretty impressive shelf life there Nick and Screwy, can't complain about that!

OP, the yeast should be fine but try rehydrating in plain water first to ensure viability. After just 30 minutes, no froth = no use. Then if you want to make up a starter, here's how I did rehydration and a starter with dried yeast, you can use thick- walled stubbies or other glass bottles if you like.

Hope this helps! :icon_cheers:

 

[TerritoryBrew]

I will just give it a go then. Make a starter and see if they awake. It is only a 'Best Before' after all.

Thanks.

 

[Ross]

Dried yeast's 2 year best before date is based on storage below 20c. If kept in the fridge you can pretty well double the best before time.
I'm not sure on freezer storage viabillity, but would guess it would be at least the same as the fridge.


cheers Ross

 

[MarkBastard]

Doesn't freezing yeast damage it though?

 

[Effect]

Doesn't freezing yeast damage it though?

if there is water there...the water expands and cuts through the yeast cells IIRC. Dried yeast, obviously, doesn't have this liquid.

 

[RdeVjun]

No worries, BBE dates are probably for room temperature storage, refrigerated and frozen would probably be different. (Beaten by Ross.)

TB, rehydration is an easy way to tell if dry yeast is viable, you can actually pitch it once rehydrated or proceed with a starter to multiply it up if need be. If you've got just a standard 20-odd litre batch of the usual strength, then once the yeast is rehydrated (i.e. frothed up, so it is certainly viable) then there's probably no need to be making a starter, just pitch the frothy water which contains the yeast and it should be happy days.
If there's any concerns that the number of active cells is lower than it should be then that's when it should be stepped up in a starter, similarly for larger batches or stronger wort they need it to be stepped up to increase the yeast population.
Also, rehydration should take only 30 minutes from pitching the dried yeast into the water, don't leave much longer or the yeast runs out of its glycogen reserve and snuffs it.

Yeah Mark, some folks advise against freezing dried yeast, but as we've seen, it doesn't seem to trouble it, I guess it is freeze- dried to begin with too? Also, freezing yeast in liquid form is certainly problematic (as Phillip relates) unless the solution is specially prepared (glycerine etc.).

BTW, in that album, the photos 7 & 8 aren't good examples of frothing up through the rehydration process, I shook it before taking those pics which was a bit silly on my behalf...

 

[TerritoryBrew]

Update...

Both yeast packages are working like little champions. Thanks for all the help.