Yeast Question

[Innes]

I have a vial of WLP028 which is about 3 months past is used by date. I'm not planning to brew anything with this yeast just yet, but I plan to in the next couple of months. I don't want to throw it away only to have to purchase a fresh vial when I need it.

My question is, can I put this yeast into a starter (1L or 2L?), let it ferment out, wash the yeast and distribute the yeast between a couple of clean and sanitised whitelab vials?

Is this basically the same as harvesting yeast from a fermenter?

 

[Wolfy]

Yes you could make a starter with it - there are likely only a small number of viable cells, so a stepped-starter might be advised (start with a small step before going to your 1-2L size) but there should be no need to wash the yeast after because there should be little trub in the starter (no break material or hops etc).
The decision is only if you make the starter now (when you might have slightly more viable cells than in a few months time) and then store the starter (which could introduce infections and/or cause issues while stored) or if you leave it in the vial and make a stepped-starter just before you're about to use it (I think this is the option that I'd go for if it was me).

 

[stux]

I would keep the vial in a cold fridge and do a multi-step starter later.

use http://www.yeastcalc.com to work out your steps

 

[Innes]

I would keep the vial in a cold fridge and do a multi-step starter later.

I have read some brewers keeping vials for several years before using them. How old does a vial have to be before its considered not viable even for a stepped starter (if it has been kept refrigerated since manufacture)?

 

[Wolfy]

I have read some brewers keeping vials for several years before using them. How old does a vial have to be before its considered not viable even for a stepped starter (if it has been kept refrigerated since manufacture)?

How long is a piece of string?

In theory you can build a starter from a handful of viable cells, but it depends on your procedures and sanitation. The vast majority of the yeast will already be dead - and not useful for anything but a stepped starter - but there is no way (without scientific techniques) that you can know how many cells are alive or how long you'll be able to store it for, it's either going to be guess work or hearsay.

 

[Nick JD]

Starving your yeast strengthens them. The sole yeast cell left in that morbid, turbid vial of vegemite is the archetypal superyeast. You have done the brewing world a favour by eliminating the bludgers of the yeast world.

Scottish yeast eugenics will result in a more German tasting beer.

 

[stux]

It only takes one viable yeast cell.

Two tricks:

1) hope that yeast cell is a non mutant
2) reduce chances of bacteria out competing the poor yeasty bite

So, start with a small step the less viable your yeast so you can get a healthy colony ASAP. I've so far used splits which are more than 12 months old with no issues.