Yeast Harvest

[graysalchemy]

Hi

On friday i harvested my yeast from the FV and placed in a sterilised jar added cooled boiled water and left it in the fridge at work over the week end. It has frozen solid!!! .

I take it the yeast will be dead? or is it worth trying to revive them?

Cheers

AG

 

[Tony]

They'll probably be fine, just thaw them in the 'fridge slowly, or if you're ready to use them, make up a starter! :

 

[graysalchemy]

Thanks for that. I am thawing them slowly and will continue to wash them. I may try out a little starter just to see that they are still alive.

:

 

[State of the mind]

Thanks for that. I am thawing them slowly and will continue to wash them. I may try out a little starter just to see that they are still alive.

:

You don't sound very optimistc. Yeast is not killed when it is frozen it is just dormant. Anticipate a longer lag phase than normal though, as the yeast has to come around. :grin:

 

SotM is right.
I've frozen my yeast cultures for many months, just alow about 36hrs for it to wake up.
I don't even bother making a starter!

 

[graysalchemy]

Thanks for that. I thought i read that when cells are frozen the cells walls rupture and you should use gycerol to prevent the cell damage. Mind you i remember my mum freezing yeast for bread making.

Thanks for that

:

 

[Aleman]

Technically you could end up with dead yeast as ice crystals form inteh yeast cells and they do rupture . . .if the solution froze very slowly I suspect that the ice crystals would also have formed slowly and therefore you may get a reasonable (albeit very low < 25%) survival rate.

To 'do it properly' you would use a 50% water/Glycerol mix at 2C . . . add yeast stir wait for 30 minutes, stir again . . . and then freeze very quickly using a really cold source . . Liquid N2 is good. You want the stuff to freeze before the glycerol separates from the water. . . . and ideally you use very small sample sizes around 2ml. . . . which of course takes a long time to grow up to a decent pitching rate

 

[State of the mind]

http://www.homebrewtalk.com/wiki/index. ... zing_yeast

This should answer most questions. :whistle:

 

[graysalchemy]

Thanks once again. I'm just going to carry on separating and washing it and if it works it works no big deal if it doesn't.

Cheers once again