Pitching on a yeast cake?

I'm planning on brewing a RIS in a few weeks and I'm going to bottle a batch of beer on the same day. So I'm planning on reusing a big chunk--if not all--of the yeast cake for the big beer. When people talk about "pitching on a yeast cake" do they literally just dump the wort on top of the old cake in the same fermenter, uncleaned, trub and all? This seems like a prime way to get an infection, but then again I could be wrong. Any tips on how much of the cake I should use and what method (the RIS will have an OG of around 1.090+)?

Thanks!

If there is no infection in the dirty vessel, why would you think adding clean wort to it would cause an infection? Yes we just rack the beer right on top of it.

I do similar style beers and end up dumping half the cake out before adding the other batch. But since you are going small to big, just use the whole cake. It'll take off like a rocket so watch your ferm. temps the first couple of days. Hopefully you are doing this in glass so that you can enjoy the fireworks once it gets going.

Like BendBrewer said, infection shouldn't be a worry.

However, I go the other direction from his method. I would put the wort in a clean carboy and then pitch an appropriate amount of the slurry so as to not over pitch. Mr. Malty has a good pitching rate calculator that you can set up for slurry to get an idea of how much you would want to pitch.

But then you have to wash a carboy.......

BendBrewer said:

But then you have to wash a carboy.......

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My fear of that scum up top and too much trub material creating off flavors over powers my laziness by the slightest little bit. My carboy collection keeps me going for a long time before having to clean a new one ...however, my garage starts to look like a bachelors sink after a few batches.

I would think that all that dead yeast and trub in the cake would create off flavors.

Why not rack the beer off the yeast. Then go back with the racking cane and suck up the top layers of yeast off the trub and put that into a beaker to settle. Then pour out the trub from the carboy, pour in your new wort and the yeast that you siphoned off the top of the trub?
Wouldnt that work to resue the yeast and get rid of most of the trub from the first beer?

I have pitched on yeast cake twice. Same fermenter, just dumped from the brewpot after chilling. Both beers came out fantastic. Definitely gotta watch the fermentation tho....both times were violent ferms that required blowoffs.

I'm switching over to yeast washing so that I get max value for my money.

Just this Saturday I pitched on the previous week's yeast cake. I just dumped my newly made wort into the dingy carboy. Today is tuesday and I just racked this beer to a clearing tank (carboy) for crash cooling. That's right. 72 hours later and my beer is ready for clearing/carbonation. I'm not sure if it was the yeast (wlp 028 Edinburg) but I didn't even need a blowoff. I tasted the beer today and it was fantastic. I think if your previous yeast cake is still fresh/young you should be ok as long as you get it off that yeast cake as soon as your newly made beer is ready.

I'm doing lagers that way. I just pour off all but about a cup or two of the yeast/trub and add fresh wort. I've done it as many as three times in a row without a problem. I could probably do it more but I always get worried after the third time and start over, cleaning my BB's and making a new starter. It hasn't caused a bad beer yet.

redalert said:

Just this Saturday I pitched on the previous week's yeast cake. I just dumped my newly made wort into the dingy carboy. Today is tuesday and I just racked this beer to a clearing tank (carboy) for crash cooling. That's right. 72 hours later and my beer is ready for clearing/carbonation. I'm not sure if it was the yeast (wlp 028 Edinburg) but I didn't even need a blowoff. I tasted the beer today and it was fantastic. I think if your previous yeast cake is still fresh/young you should be ok as long as you get it off that yeast cake as soon as your newly made beer is ready.

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Yeah, freshness is really the heart of the matter IMHO. After spending several hours brewing an all grain batch, you've also got to bottle or keg a previous batch at the same time. I usually do it while the wort is chilling to pitching temps...I don't think I could hack it if I wasn't kegging. 4+ hours of all grain, bottling and capping 50 beers, AND the final cleanup at the same time hurts my back just thinking about it.

I've been bottling while the boil is going. I then "wash" the yeast and pitch it into my new beer. If I could get away with skipping the "washing" part and just pour the cooled wort onto the cake, I may try it.

Newton said:

I would think that all that dead yeast and trub in the cake would create off flavors.

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When you buy "Yeast fuel", that is essentially corn sugar and dead yeast. Good yeast will "eat" the dead yeast during fermentation from my understanding. That is why at least I have seen a trend to leave the beer on the cake for 3-4 weeks to allow the yeast to clean themselves up. Just my opinion though.

I pitch directly onto whole used cakes quite frequently without issue or concern.

I have pitched straight into the "dirty" carboy several times and never had an infection. I also wash yeast and store in mason jars, but I've always felt that the additional steps are increasing my risk of infection. I have never experienced off flavors from reusing an entire yeast cake, so whenever possible I try to use this method. My one thing is that I won't do it for more than one reuse, because I have some sort of irrational fear of the huge amount of gunk after the second batch. So once I've done two beers on a cake I wash the yeast. I'm pretty sure that this is completely unnecessary, and one day I hope to get past my phobia so I only have to wash carboys every 3 brews instead of two, but for now I'll put up with since I just built a carboy washer.