Does yeast need to be 'washed' to be re used?

[Muskogeee]

Forgive me if this is a newbie question, but as the topic says, do you have to go through the process of washing the yeast in order to re use it? Could I just siphon out the carboy leaving the yeast cake at the bottom, and just refill with new wort and agitate it?

Only reason I ask is that I'm moving up to a 5 gallon system for my next adventure, but I still have ingredients for one more 1 gallon batch, minus the yeast. I have a 1 gallon batch still going that'll be ready to bottle in a couple days so if I could just cook up the wort and dump it into that carboy it'd be great.

 

[d3track]

Use maybe 1/4 to 1/3 of the yeast cake.

 

[JonM]

Yes, but it's over pitching.

You can dump some of the cake into a sanitized Mason jar or beer bottle and use the remaining yeast cake for your next batch. Not precise, but it works pretty well.

Know what you can do? Make a 1 gallon batch, ferment it out and use the 1 gallon batch's cake on your first five gallon batch! (That might be a modest overpitch, but not by much)

 

[mtnagel]

5 gallons on top of a 1 gallon batch will most likely be fine (depending on gravity of the new batch). I would not wash that as you will lose a lot a yeast in the washing process. I've purposely made a 1 gal batch of small beer to purposely reuse for the next 5 gal batch. You can use a website like http://www.yeastcalculator.com/ to see how much yeast you created in that 1 gal batch.

Now if the first batch was 5 gallons, that would most likely be a major over pitch onto the next batch.

 

[mtnagel]

EDIT: now maybe I was reading it wrong. Pitching the whole yeast cake from a 1 gal batch onto the next 1 gal batch would most likely be a big overpitch. (If that is in fact what you are doing).

 

[flars]

No, you don't need to rinse the yeast to reuse it, but you can't pitch the new wort on top of the yeast cake of the previous brew. It would be a massive over pitch. Swirl the yeast into solution with the left over beer. Pour into a sanitized jar.
Estimate 2 billion cells per ml,if there is visible hop debris, for pitching the needed amount into the next beer.
Good blog to read up on reusing yeast.
http://www.woodlandbrew.com/2013/01/yeast-washing-revisited.html

 

[latProd]

So....I've never done this, but yeast is expensive. Sounds interesting.
Does this mean if I brewed an IPA, for example, and just removed the yeast cake after fermentation into a sanitized sealed container, I could store this and use it on another brew ?
How would you even know how to calculate how much to use ?

 

[mtnagel]

Yes you can, with some caveats:

- Only reuse yeast from lower alcohol beers. I've seen 1.070 OG quoted as the upper limit.
- Reuse within 2 weeks (This was what they said in the Yeast book).
- Try to go lighter to darker (pale ale to stout, not the other way around).

As for how much, use Mr. Malty's "Repitching from slurry" tab - http://www.mrmalty.com/calc/calc.html

If you want to learn more about how much to reuse, read some of this thread - https://www.homebrewtalk.com/f163/why-not-pitch-your-yeast-cake-166221/