Yeast Harvest And Culture - Help Req

[PostModern]

I'm brewing an ale atm (as per my "Panic Stations" thread in "Is My Beer Ruined?") and want to harvest some of the yeast from the trub for a later batch of Pale Ale. I'll be putting a wit-like brew down on top of the trub as well.

Anyway, my questions specifically are:

1. How can I keep some of the yeast alive in my fridge for future pitching?
2. If I want to remove most of the trub, as it contains heaps of cascade hop reside, is it possible without disturbing the yeast cake or reducing the yeast population too far?

 

[Doc]

PM,

If you want to save some of your yeast cake, this is the way I've done it in the past.
When you are bottling/kegging your beer make sure you leave some dregs in the bottom of your fermenter (normally I have a little bit left over anyway). I then swirl it all around to mix some of the trub in with the liquid, then bottle that in a long neck and store in the fridge.
When I want to use it I get it out of the fridge for a few hours to let it warm up then pitch into the new brew.

As for getting the hops and stuff out you probably need spoon out what you can see and acid wash the rest.

From White Labs FAQ
What is acid washing for yeast?

Acid washing is done to cleanse the yeast slurry before repitching into the next batch of wort. Acid washing consists of adding food grade sulfuric or phosphoric acid to the yeast until the pH level reaches 2.5. At this level of pH most bacteria are killed. Acid washing does not kill wild yeast cells which could still contaminate your wort.

Cheers,
Doc

 

[PostModern]

Ah OK. I'm racking the beer, so I'll be leaving most of the slurry behind. So I just bottle some of it and wash it before pitching. Sweet.

Thanks again Doc.

 

[Doc]

No worries.
Here is an in-depth article and method on yeast washing that I had forgotten about.

Cheers,
Doc

 

[PostModern]

I had a go at this last night. The recipe had 125g of hops in it, so there was no way of getting anything thru the tap one the beer was racked off. I ended up putting a sterile brewingspoonful of the trub into a sanitised glass and covering it in warm water. It stratified by morning, but the yeast layer looks pretty thin. I may have to put it into a mini-wort to get a bigger population out of it. I couldn't belive how much hop reside is left. 125g looked like a handful until now! Anyway, I was thinking I might be more successful harvesting cleaner yeast out of the dregs of the secondary fermenter after I rack to my bottling bucket.