Yeast harvesting / washing question

[lhooq]

I'm a bit confused about this - seem to find conflicting advice. I've finished fermentation of one batch, and then swilled out the fermenter and left the results to settle in a clean bottle (that's what's in the photo), presumably this is mainly trub and water. What of this should I keep, and how? I would happily make a new starter when I wanted to use the yeast again so don't need to have loads, but I do want to keep the right bit and ideally not all of this as it's about 3 liters in total and will take up loads of fridge space!

Thanks for any advice (the yeast was Wyeast 1469 West Yorkshire incidentally).

 

[xozzx]

I might (probably) be wrong but I think its the white layer in the middle, sitting ontop of the brown layer at the bottom.

I started recently using liquid yeasts but instead of washing the trub after fermentation I overbuild my starters and keep some yeast back for future brews. I have started making upto 4 vials of each yeast I use and keep these in the fridge so I have some backups if I mess anything up.

 

[the_quick]

how long can you keep yeast in the fridge?

 

[cushyno]

Yep, the white layer is the yeast. As the brown layer is on the bottom it must have settled first. That's the heavier trub. The trick is to allow the trub to settle first then pour the rest off the top into another sanitised container. Then you'll be left with just yeast (and maybe a little trub) suspended in the liquid. When the second container settles, pour off the liquid leaving just the white layer of yeast.

Depending on the yeast, if it is a highly flocculating yeast it may sink to the bottom before your trub or mixed with the trub so you can't really separate it out. This doesn't stop you from saving and reusing.

I have managed to save one separated yeast (which was originally a dried sachet) and another that was just mixed with trub (originally liquid smack pack). They've both worked fine after being refrigerated for a couple of months.

 

[Dutto]

Weirdly, I can't see the "thin white line" that should be sitting between the liquid on top and the dead yeast on the bottom!

The thing is, that "thin white line" is the stuff your are needing to save; as per this photograph.

The photograph shows the situation after only about 40 minutes of separation time. After 24 hours in a fridge, the yeast and trub have compacted down so that the liquid can be almost completely poured off; and in many cases the layer of live yeast can be "rolled up" with a sanitised spoon so that very little trub is picked up.

The live yeast is then placed in a smaller jar and stored in the fridge for up to two weeks (*) before using it for a "Yeast Starter".

(*) I think it's actually up to a month but I've never been that brave.

Enjoy!

 

[BeerCat]

how long can you keep yeast in the fridge?

Years

 

[Dutto]

Er ...

"In Yeast (White & Zainasheff), they have a table of the reliable and max shelf life of yeast storage techniques:

• Harvested slurry: 2 weeks / 6 weeks

People report success with fridge-stored slurry on much longer time frames. I think White & Zainasheff are being somewhat pedantic; the amount of mutation you'll see in a handful of months is probably both very real, but also not particularly noticable to a homebrewer's beer or palate, all things considered."

For me, two weeks are enough.

https://homebrew.stackexchange.com/questions/10572/how-long-does-harvested-yeast-keep

 

[Zephyr259]

Those pictures are some of the most helpful I've seen, folks are always on about "the white/paler layer" and I can never see it but can in this case. I'm also once for overbuilding starters, I'll keep 100 billion cells on hand and based on an online calculator they'll lose about 20% viability per month which leads to 25% after 6 months, at that stage a 500 ml starter bumps them back to 100 billion cells. That's assuming I've not used the yeast before the 6 month mark.

Now that I have a conical, I guess i should try harvesting my slurry since that's one of the biggest benefits of the conical.

 

[lhooq]

Thanks for the advice, very helpful. I think I will try Dutto's spoon technique. No disaster if this one doesn't work out.
And I've already overbuilt my starter for tomorrow's brew so will be much easier to store that one. Never thought of that before reading about it here.