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How to harvest yeast?

What is the best method to harvest yeast? While this may sound strange, once I rack my current brew out of the carboy, can I simply rack the new brew over the cake in the carboy from the previous brew or do I need to transfer the yeast to a cleaned and sanitized carboy first? This will be the first time i’ve attempted to reuse yeast. I’ve been worrying about this for about a week so I need a little nudge to get going on my next brew.

You can pitch directly on the cake but this, in most cases (depending on gravity of the wort) will be a huge over pitch. For most ales you only need around 1/4-1/3 of the yeast cake and most lagers 1/2 of the cake.

What’s the gravity of the brew you just racked and the gravity of the brew you plan to pitch on the cake?

I have extra fermenters, so I’ll usually plan my brew days such that I can transfer beer A to secondary while I’m brewing beer B. Beer B goes into a clean fermenter; I use a sanitized serving spoon to transfer yeast cake to the new fermenter. 3-4 spoons is about 1/3-1/2 of the cake.

I know I’m over-complicating, but I can’t bring myself to reusing a fermenter with all that dried krausen-gunk up the sides.

“What’s the gravity of the brew you just racked” - dry irish stout at 1.042

“The gravity of the brew you plan to pitch on the cake” - imperial stout at 1.086.

I think i’ll be ok with the pitch since it has such a high O.G. What are the consequences of an over pitch?

[quote=“JMcK”]I have extra fermenters, so I’ll usually plan my brew days such that I can transfer beer A to secondary while I’m brewing beer B. Beer B goes into a clean fermenter; I use a sanitized serving spoon to transfer yeast cake to the new fermenter. 3-4 spoons is about 1/3-1/2 of the cake.

I know I’m over-complicating, but I can’t bring myself to reusing a fermenter with all that dried krausen-gunk up the sides.[/quote]

Yeah, I’m in the same boat as you. I’ve never pitched onto a cake before for this very reason. Plus I brew a lot less often so I’ve never actually brewed on the same day that I’m transferring to secondary or bottling. In fact, I always brew the day AFTER I bottle a batch so I always have the yeast in the fridge for a day when i harvest/repitch.

For that imperial stout, use the entire yeast cake. It won’t be an overpitch.

If you do overpitch, the effect depends on the yeast you are using and the beer you are fermenting. The yeast won’t go through as much of a growth phase when you overpitch, which can sometimes lead to the same kinds of off flavors you get from underpitching. But in practice it’s pretty hard to overpitch in a homebrew setting.

[quote=“Misfit”]“What’s the gravity of the brew you just racked” - dry irish stout at 1.042

“The gravity of the brew you plan to pitch on the cake” - imperial stout at 1.086.

I think i’ll be ok with the pitch since it has such a high O.G. What are the consequences of an over pitch?[/quote]

In my experience very little other than a violent fermentation and the need for a blowoff. There will be less ester production as well. Some people claim there could be a risk of autolysis (excessive dead yeast cells). In my experience, I’ve never noticed any of these issues.

[quote=“rebuiltcellars”]For that imperial stout, use the entire yeast cake. It won’t be an overpitch.

If you do overpitch, the effect depends on the yeast you are using and the beer you are fermenting. The yeast won’t go through as much of a growth phase when you overpitch, which can sometimes lead to the same kinds of off flavors you get from underpitching. But in practice it’s pretty hard to overpitch in a homebrew setting.[/quote]

+1 deja vu

and for the record…again :wink: I ain’t afraid of no krauesen gunked carboy! Sanitary beer came out…more going back in!

I’m a little more concerned with contaminating the yeast during harvesting than I am with the sanitary gunk. Should be fun! Thanks everyone for the advice!

What I do when I’m harvesting yeast for later use is spray the inside and outside of the carboy neck with sanitizer and just pour it out. Of course I pour out of a plastic carboy so it’s much easier for me. I would suggest using extreme caution if you are lifting and pouring out of a glass carboy.

I finally got around to brewing my Imperial stout and bottled the dry irish stout during my boil. Pitched the imperial right on the cake in the gunked up carboy. Once I had the imperial racked to the the yeast cake, I shook the hell out of it for a few minutes. Hooked it up to a blowoff tube and will be watching for activity. On a side note, the dry irish tasted delicious even before conditioning. Can’t wait for that one.

Here is a pic of the cake racked the imperial stout to. Based on this photo, anything I should be concerned about.

Looks like a good clean yeast cake. Should work well for you.

I really appreciate everyone’s input on this. This is the first time i’ve reused a yeast so it’s been rewarding to see positive results. Right now my imperial stout’s fermentation has taken off and the blowoff is bubbling more than the Lawrence Welk show.

Thanks again!

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