Yeast viability in 25ml of washed yeast after a year in the fridge

[Shane Phelan]

Joey and myself were making slants the other day for the capital brewers barrel and I bought in an old vial of trub with WLP007 yeast in it. I tried to wash it but it was still black from the imperial stout I last made with it and I had assume it was all dead.

We decided to streak a small sample of the yeast on a Petri dish for two reasons. The first was to see if the yeast was dead or not and the second was to see if anything else was in there! In summary streaking is the process of 'spreading out' a culture to see if there are any contanimants and to allow a single colony to be isolated. It looks like this when done:





As you can see from the picture the viability was quite low and only the first set of streaking grew with a couple of colonies with the second streaking. There were no other contaminants which I was surprised about given that I had used that yeast for 2 or 3 brews while washing it each time!

Really the point I am making here is that yeast will most certainly survive in your fridge for more than a year, you would need to start off with a tiny starter but all the same it would grow.

[Hop Bomb]

Thats good to know.

If I make a 250ml starter from a slanted yeast vial will that give me 100% viability as Ive just grown fresh yeast from that colony in the slant?

[delzep]

Is it any different really to harvesting yeast from a bottle conditioned beer thats of a similar age (and you don't know where that has been stored or transported)?

[RichC]

Hope you can read this. It's stepping up from a plate from Chris whites book

[Hop Bomb]

Thanks for that Lars. I must buy that book.

[Shane Phelan]

I also want to read that book before publishing the slanting guide.

[Hop Bomb]

You got any slants you'd like to trade Shiny? Ive three growing right now. White labs: Cal ale, Super San diego & Irish ale (all cloned from new viles)

[Dr Jacoby]

I also want to read that book before publishing the slanting guide.

I have a copy that I could lend you. I'll bring it in to work next week if that suits.

[JoeyD]

Just to clear it up.  Might not have explained it well to Shane.  Its not necessarily an indication of viability, more the concentration of the yeast in the vial.  The concentration would vary depending on how much water he used to wash it and a couple other factors.  Viability can only be measured using a dye like trypan which stains dead cells blue but cant stain live cells.  You then have to look at them under a microscope and count the percentage dead.

We just took a loop full (small drop)  and spread that on the plate.  Because we didnt know the concentration of the yeast we streaked the whole plate but it was a low concentration and only made it a bit of the way round.  The main idea of the streak is to obtain single colonies... which we did.

You will very rarely if ever have a 100% viable solution.  All the cells are at a mix in which they are at different stages of the life cycle.

[Shane Phelan]

I also want to read that book before publishing the slanting guide.

I have a copy that I could lend you. I'll bring it in to work next week if that suits.

Yeah that would be great! thanks!