yeast cake re-use

[pharaohpierre]

I'm brewing an IPA now and I plan on brewing the exact same IPA again next week. I plan on brewing on the same day that I rack off primary. I also plan on keeping the yeast cake on the bottom of the fermenter and then racking the new wort on top of that.

My question is that the yeast cake gets to be like 1 inch thick, so is that too much yeast in fermenting the new beer? Also, if I keep the yeast in there and pour the new wort on top will that end up doubling the size of the yeast cake to like 2 inches? Any experiences and thoughts?

 

[boydster]

You only need about 1/4 of the yeast cake. You want the yeast cells to divide so there will be some young, healthy daughter cells to ferment the beer. Right now, you have exactly the right number of cells to do the job, so they won't divide much, but those cells are getting old and scarred and may not produce the best results - the chance for poor fermentation would grow with each brew if you pitched on the entire cake multiple times. Getting rid of 3/4 of the yeast cake will allow the colony to grow and give you plenty of healthy new cells.

 

[sfgoat]

Many will tell you that pitching directly on top of the yeast cake will result in massive overpitching. They are probably right. But I do it all the time and get great results. You would probably be fine just scooping a cup of the yeast cake and pitching that. But like I said I am lazy and just like to dump my new wort directly on the cake. This will produce more yeast but not the way you are thinking. The existing yeast will take care of that wort so fast that reproduction will be minimal.

 

[eastoak]

the minimal reproduction spoken of above is the problem, you want the yeast to reproduce. i've pitched on an entire cake and it does make a beer but not as good a beer as one with a correct yeast pitch.

 

[mbbransc]

Aren't most of the yeast characteristics created during propagation? So if they yeast aren't multiplying, you aren't getting any 'flavor' from them? I guess that'd be OK for a Cal Ale yeast (something with minimal flavor anyway).

I plan on brewing a small 3.5gallon batch of pale ale (1.050) and then racking an imperial stout on the yeast cake. Going from 1.050 to 1.090+ should motivate the yeast enough to propagate, wouldn't you think?

 

[boydster]

Yeast flavor characteristics and healthy, young daughter cells that will survive longer than their old, scarred parent cells are created during that phase. Going from 1.050 to 1.090, assuming same volume, I would probably use a little less than 1/2 the yeast cake.

 

[mbbransc]

What's the best way to remove yeast without infection? Sanitized measuring cup?

 

[BeerLoverHere]

Dump half to 2/3 of your yeast cake out. Put new wort on top. Should be good to go!

 

[EarlyAmateurZymurgist]

Now, that's a good example of the KISS principle! :rockin:

 

[BigFloyd]

Dump or scoop 70-75% of the existing cake out. Either way will work fine.

When you rack the first beer off, it's a good idea to leave a thin layer of protective beer atop the yeast cake.

 

[pharaohpierre]

Since I'm using a carboy, I can't really scoop anything out. So I guess I should leave a thin layer of beer on top of the yeast cake and shake the hell out of it so the cake becomes fluid enough to empty out. Then empty about 1/2 - 3/4 of the yeast and leave the rest in. Then rack the new wort on top of that. That sound like a good plan?

 

[mbbransc]

This sounds like an opportunity for a great experiment.

How about removing 1/4 yeast cake to another fermenter and splitting your batch between the two fermenters and see how they taste differently based strictly on yeast starter size.

I think this would be interesting because 1/4 yeast cake should be more than enough for a batch of beer and the 3/4 should be well over-pitched. I believe I'm correct in that most commercial breweries over-pitch. It would be interesting to see what the differences would be on a homebrewer level, if any.

I don't have a mash tun large enough to conduct the experiment.

 

[eastoak]

I believe I'm correct in that most commercial breweries over-pitch.

i have not heard that but i wonder why that would be the case. the commercial brewers that i know try to get their yeast pitch right for the gravity of the beer they are fermenting.

 

[mbbransc]

I've always heard they over-pitch; maybe I'm making that up.

I assumed it was because time=money for them. The sooner they can empty a fermentation tank, the sooner they can refill it.

 

[pharaohpierre]

interesting idea mbbransc. Looks like I'll be needing to get a second fermentor (although I guess I could use my secondary)