Racking onto yeast cake.

[Ashebrewro]

I have been reading about reusing yeast, washing yeast and the like. I am going to brew an APA monday OG 1.049 using US-05. I am thinking about reusing some of the yeast for a IPA OG 1.064. I know using the whole yeast cake would cause an explosive fermentation. My question is how much of the cake to reuse? I would prefer to not take the time to wash the yeast and rack the APA to secondary for dry hopping and have the IPA ready to pour on the portion of the yeast cake. Any advice is appreciated.

Cheers!

 

[flars]

I have read about 1/2 the yeast cake would be used for the 1.064 OG beer you are planning. Can't verify this is correct. I have never used the yeast cake before without some rinsing.

 

[AerationStation]

Personally I would pour out all the cake in to different mason jars. Most mason jars have some sort of measurement on them, usually in mL.

Go to a yeast calculator (jz is my favorite, check out mrmalty.com) and plug in your numbers for the next beer. The default setting on mrmalty is good for the usual compaction of yeast cake. Then all you need to do is estimate volume.

The benefit of doing it this way is you'll be closer to the desired pitch rate and will also get a chance to clean and sanitize the fermentor

 

[LLBeanJ]

+1 for MrMalty. Using default settings, it says you'll need about 118 ml of slurry for 5g @ 1.064, which is ~1/2 cup.

 

[Ashebrewro]

I was wondering about the mrmalty settings for just pouring the yeast cake and trub from the fermenter and using that. I wasn't sure how to adjust it without rinsing the yeast, so you are saying the defaults are set for unrinsed yeast slurry straight from a primary?

Thanks for the help.

 

[LLBeanJ]

Yeah, I'm pretty sure it's close enough. Whenever I repitch raw slurry, I just go with the default settings and call it good.

 

[mtnagel]

I was wondering about the mrmalty settings for just pouring the yeast cake and trub from the fermenter and using that. I wasn't sure how to adjust it without rinsing the yeast, so you are saying the defaults are set for unrinsed yeast slurry straight from a primary?

Thanks for the help.

This will give you an idea how how to set those sliders.

 

[masonsjax]

Washing is a bit of a misnomer in this situation. True yeast washing involves an acid wash. What some are doing with the boiled water is rinsing and is a waste of time IMO.

When I reuse a yeast cake, I dump out most of it leaving about a pint if it's pretty free of hops trub and going into an average gravity beer, up to about a quart if it's got lots of trub and/or will be eating a high gravity wort. You can save the unused yeast in a sanitized jar in the fridge (no rinsing needed) and use it within a month or so. If you won't use it that soon, make a starter first. If you store it long term, decant the spent wort and replace with fresh wort every 4-6 months or so.

 

[Aonghus]

I have pitched directly on top of the yeast cake before with no ill effects. Just consider it a giant starter.

If you want to control the fermentation, put the fermenter in the tub and fill it with several inches of cool water.
I did exactly that last beer I made.
I made a barley wine last weekend (using 3rd generation Pacman cake + 2 liter starter). It took off right away and when the temp strip read 68 I went ahead and filled the tub (as described above). I was able to hold the temp at 64 after that. Barley wine started at 1.098 and five days later was at 1.022 (with a lot of c02 in suspension).

 

[Calder]

Mr. Malty is lousy for slurry. Don't waste your time.

Regardless of the size of the pitch, the yeast will reproduce to about 6X the recommended pitching quantity during the first 24 hours. Obviously some have died by the time the beer is racked or bottled.

I generally assume at the end of the brew, the amount of viable yeast is 4X the recommended pitching amount. Therefore, for a beer of similar gravity, and volume, you would pitch about a quarter of the cake.

Mr. malty would have you believe 90% of the viable yeast in slurry is gone after a month ........ which is obviously wrong; this is why I don't recommend Mr. Malty for slurry. .... Why is slurry OK after 4 weeks in the fermenter at room temperature, but not after 4 weeks (in the same beer) in the fridge.