maintaining a culture of yeast

[Jeltz]

is it worthwhile buying a decent ale yeast then preparing a starter and keeping a culture?

Are there pitfalls to watch out for and how long can a culture be kept?

 

[orlando]

Yes it is. In fact you can keep stepping up till you have enough for 2 brews then keep back 1/2 for when your FV becomes available. Alternatively you could pitch the whole lot and then top crop the yeast after a day or two. The key here is to keep a watchful eyen on the brew. You don't want the very first lot of yeast head as this contains stuff like hop resins. Scrape the very toplayer of that off and then wait until the krausen has rebuilt. It is this yeast that is at its peak of viability and vigour. Hopefully it goes without saying that scrupulous sanitation bordering on sterility is what you need for all this and a copy of Yeast by White & Zainasheff would be very handy too.

As for viability, if you store it at around 2-3c in the fridge and use within a month you will lose about 1/2 the yeast cells but can bring it back into better health by making another starter with it.

 

[Kev888]

This is something I'd like to hear about too!

From what I can discover, you can ferment/collect and ferment/collect etc etc, and the yeast will renew themselves each time (though in time will evolve to your own strain, which may be good or bad). In theory that process can go on infinately but the chances of an infection are cumulitive too, so it has more risk of loss/disater attached.

Or you can split the vial by growing and splitting into bottles/batches, or (ideally) by spreading directly across autoclaved slants or agar plates; they will last a while but they won't stay viable for ever.

Some people have tried freezing liquid yeast, which can split the cells and destroy them, but a small proportion survive and (being frozen) do so for a longer period, though to use them you have to be selective at almost a cell-level, and grow from a 'teeny' starter upwards.

I've also wondered about taking just small portions at once from a fresh vial for each brew (with a 'very' sterile lupe or something) and growing them up more. On the basis that whilst the remaining yeast will gradually decrease in viability, white-labs/wyeast etc have a 'very' high level of sanitation so it could be better than me trying to start from such lower viability than trying to propogate it in my kitchen. But I've not found much info on the pros and conns of that.

Cheers
kev

 

[Jeltz]

Actually what I was thinking was using a sachet to make a starter the split the starter down to 3 and use a third to make another starter while putting another third in the fridge.

Then use them it create additional starters and split them etc..

I hadn't even considered recovering cultures from fermentations.

 

[Kev888]

If I'm understanding correctly, thats a little like splitting a vial (making say a demijhon-full and splitting it into smaller bottles - one to use and some to save), and it works.

But dried yest is 'considerably' more economical than liquid yeast, to the point where the financial benefits of buying less and growing/splitting it is pretty debatable, especially if you then consider the added risk of infection. Dried or liquid malt used in starters is pretty costly (relatively speaking); if you brew from grain, you can collect very late runnings (otherwise unusable for your main brew) and render them down to something suitable for the low gravity wort of a starter, but its still a lot of effort/mess.

Personally, I think the only time i'd try to extend dried yeast would be to evolve it; for example US-05 seems to be a lot more vigorous as harvested/re-used slurry than from fresh/dried.

Cheers
kev

 

[pittsy]

you don't want to bother with dried yeast for starters really , use liquid and get 8 pints of water and 500g of light dried malt , boil ,cool etc pitch yeast , (1040 og) ferment for a week , mix well , split into 330ml/500ml plastic bottles , store in fridge till needed to make 1 starter (1l of water and around 100g, ferment for around 3 days) , you will have 10/12 yeast bottles and when you get downto your last 2 , start all again with step 1 to make 10/12 more bottles . you can do this at least 5 times so for 1 liquid yeast vials you can make around 50 plus vials , p.s liquid yeast gives far better results