Freezing and re-using yeast

So given that I've spent a lot of time, effort and money into making a good yeast starter, what are my options once this baby has done all its work? How many generations of use are OK before the yeast is no longer viable for a style?

I'm seriously considering ditching my little fridge in the garage for a freezer, that way I could safely store all my hops and yeast in there to be used as and when. Basically the information I gather here will determine whether I go for it or not

I'm basing a LOT of the following on assumptions but I just wanted to put forward my train of thought in order for it to be clarified.

I've made a 5L starter, I'll pitch this into a lager and allow primary fermentation. Once finished, I want to save and store the yeast for the next batch. I'm assuming this 5L starter would be considered the first generation?

Assuming I split the slurry into 2 batches (is that OK, could I split it further after a 5 gallon primary ferment?) do I just put it into a sterilised freezable container and dump it in the freezer with a tiny amount of leftover wort? I read about glycerine (expensive stuff per litre) is this stuff necessary? Am I right in saying this would be second generation?

If I then use each batch and repeat the above process I will be left with 4 frozen batches to be used at a later date. Is this the 3rd gen?

My thinking is that I wouldn't take it past the 4th generation as after that level I would have had MORE than my moneys worth from the yeast and I wouldn't want to risk re-using time and time again.

With all of the above being correct this would give me 15 batches of lager from one vial of yeast, not half bad, and I would be over the moon. Splitting the slurry into 3 or 4 would clearly give me a lot more but I wasn't sure if this would be viable with the freezing process etc.

Any information would be great, thanks :)

there are other threads about re-using yeast, but here's my take on things.

when you finish the brew, the leftover stuff is mostly dead yeast, and some live yeast - this needs to be washed, and left to stand, etc to just end up with the live yeast - and then started again to provide a good yeast colony.

this can then be frozen - I think the gelatin is used to lower the freezing point of your solution so that you don't get ice crystals - these can rupture the cells of the yeast... something like that anyway.

I believe that this will be your second generation. I don't know how many generations you can have but I do know that after a while the yeast will have mutations which will eventually be detrimental to what you're after. At a guess, and this is just a guess - I'd say you're about right with 5 generations.


Edit to add links to previous threads

http://www.thehomebrewforum.co.uk/viewtopic.php?f=40&t=26367
http://www.thehomebrewforum.co.uk/viewtopic.php?f=31&t=32687
http://www.thehomebrewforum.co.uk/viewtopic.php?f=31&t=14899
http://www.thehomebrewforum.co.uk/viewtopic.php?f=21&t=17698

You need a mix of Glycerine and water

2 parts washed yeast 1 part glycerine and 1 part boiled and cooled water.

I make up into 50ml Centrifuge tubes which have been sterilised. Put them in a cold freezer. If your freezer is modern then it is likely to have a frost free cycle which actually raises the temp. If so you need to further protect the samples in an insulated box. I am going to get a small 5L cooler box and line it with more polystyrene insulation.

:thumb: :thumb:

graysalchemy said:

Put them in a cold freezer.

Click to expand...

:wha: :nah:

Ie the coldest part and the coldest setting.

I know GA, just saw the funny side out of context!

:thumb: :thumb:

I'm thinking of doing the above, storing my yeast samples in old white labs vials, but I'm not 100% on sanitising / sterilising them. Am I OK with using videne or do I need to go one stage further? Loads of people on the net seem to talk about pressure cooking test tubes etc, but I'm not sure the plastic tubes would stand up to that, let alone a prolonged boil.

All the stuff I've read says to be even more particular about cleanliness and sanitation than usual.

I used to work as a technician in a medical research lab and routinely autoclaved plastic consumables such as tubes and pipette tips, so I don't particularly see a problem with sterilising the tubes in a pressure cooker, but it will depend on the plastic from which they are made (any indication on them?). They don't need to be submerged in water - the steam will do the job, but if you leave the tops on, loosen them so the steam can enter them. A bit of autoclave steam indicator tape might be helpful to show you when they're sterile, and if you leave it in place until you need them, you'll always know which tubes have been steilised, and which ones haven't.

Dennis

hmmm... I might give it a shot and see what happens then. I was worried that they would melt/deform. I think they are made from PET.

Boil them in water for 10mins. Should do the job.

I use a baby bottle steam steriliser seems to do the job but obviously not as sterile as autoclaving them or pressure cooking. :thumb: