Do yeast really clean up after themselves?

[JONNYROTTEN]

Whats your take on the subject.
The general consensus is to leave the beer on yeast a few extra days to clean up...Then it has been stated that when the yeast is done its done and that's it. The reason the flavors/off flavors seem to come together/fade is time and sitting on the yeast cake has nothing to do with it and racking directly after FG will make no difference. Two totally different opinions on the same subject.

 

[Decimotox]

My take is that I always give it an extra day or two than I think it needs. No harm in doing that...in fact, it helps the liver out a bit

I'm sure the yeast do clean up after themselves a little bit, and thanks to them, but for those who bottle right as FG is achieved, they may not even know what the yeast have already done or not done. It's all subjective and preference in the end. I like to give it that extra time so that if they truly do clean up or whatever, it can only help!

 

[oujens]

I do think the yeast play a part in the maturation process of beer, but I don't think you need to leave it in the primary for an extended period. My opinion is whether you leave the beer on the cake 2 weeks or 4 weeks you will end up with the same result. My experience has been it usually takes about 6 weeks for my beer to have an optimal flavor profile. I'm not talking about off-flavors disappearing, but the flavors start to blend better. If you keep the beer on the cake longer it will appear the time for your beer to reach the stage is shortened. In reality it took the same time to mature as it would if you pulled the beer off the cake at 2 weeks. I wouldn't rack immediately after I think fermentation has ended, but I don't see a need keep it on the cake for an extended period of time either. For an ale I usually rack at 10-14 days depending on schedule and have no issues. Gelatin keeps the beer clear.

 

[STMF]

From what I have read (not just what people are repeating without knowledge) is that yeast clean up while they are fermenting. So, when its done its done.
It will not hurt to leave it a day or two so if you are not 100% sure or i a hurry, you can do that.

 

[Brewski_59]

What time period are we talking about? When you say the yeast is done, is that when you see activity cease? That could be 4-5 days after pitching. I've recently added a Tilt hydrometer to my set up so now I have a means to see a trend. What I see is a rapid drop in gravity in 3-4 days. then the next 4-5 days a 1 point drop per day. After that it looks done. I do see some reduction of gravity but it slows to a point every 3 days.
I'm not saying this is as accurate as a real hydrometer but I do like it to monitor fermentation progress over time.
Now what happens after this point in time? From what I read the yeast will re absorb compounds expressed during the active phase. We use this to our advantage by doing a diacityl rest for lagers right?
I think you can test this yourself. just split a batch between two fermenters. crash one when it stops any visible activity. Crash the other a week later. see if you notice a difference.

 

[Toxxyc]

Opening up this subject again. There's an argument - do yeast "clean up" after fermentation, and is there any evidence for that? I know after fermentation I leave my yeast in the fermenter for a good week or so longer, just because my beers tend to taste better. I don't know how that compares to a beer that is bottled IMMEDIATELY after fermentation.

What I mean is this - if you make, for example, a nice and crisp lager. It ferments for 10 days, and after 10 days you hit FG, say 1.005. It's not going to go lower. So what difference will it make if you, for example:
1. Rack off the yeast cake and lager the beer at near freezing for say, 3 months, before bottling.
2. Rack off the yeast cake and let the beer sit in another vessel at fermentation temps for, say, 2 more weeks, before bottling.
3. Bottling straight out of the fermenter and letting the beer bottle condition.

What's the difference, and is there any studies or anything done on it? I got asked the question and shot the guy down for saying it's fine to transfer the second you hit FG, but I'm not the type to punt stuff without know why or how, so now I'm asking - is he correct?

 

[Vale71]

Opening up this subject again. There's an argument - do yeast "clean up" after fermentation, and is there any evidence for that?

There's about 150 years of scientific research on that. The only question is how much time have you got?

One misconception that needs to be cleared from the table though is that the yeast cake has nothing to do with cleaning up (i.e. maturation) as that yeast has gone dormant and can only die and contribute autolysis off-flavors. The yeast doing the cleaning up is the yeast that is still in suspension in the beer and will remain there for a very long time unless you're one of the few homebrewers who have gone as far as actually filtering their beer. Failing that if you think you can "remove" the beer from the yeast you're just deluding yourself.

 

[Toxxyc]

Yes, see, that's the kind of research I want. Because I know the yeast cake isn't just dormant. If it was, it wouldn't work to just pitch on the yeast cake. About 1/3rd of the yeast in there (last time I checked or heard) is still alive. So I want to know what the hell the story is here. If the yeast cake doesn't contribute anything, I'm just going to rack off the yeast cake ASAP, get the next brew on and then quick-condition the beers in no-chill cubes like I've been doing the past few brews.

 

[Vale71]

Yes, see, that's the kind of research I want. Because I know the yeast cake isn't just dormant. If it was, it wouldn't work to just pitch on the yeast cake.

Why wouldn't it work? Dormant does not equal dead (although more and more individual cells will die as time goes by). When you pitch on the yeast cake you provide fresh nourishment and oxygen that will allow it to become active again.
Yeast needs direct contact with the beer to perform any processing, be it primary fermentation or clean-up work. Why would one think that yeast sitting at the bottom of a vessel is responsible for processing beer it cannot come in contact with instead of yeast that is suspended throughout the liquid? In "green" beer (beer right after the end of fermentation) there are still millions of cells per milliliter of suspended yeast.

 

[jgmillr1]

as that yeast has gone dormant and can only die and contribute autolysis off-flavors

Is there such a thing as doing a 'sur-lie' beer? Autolysis creates such nice nutty flavors that can add complexity to some white wines. I wonder if some ale styles would also benefit from it.

 

[hottpeper13]

Why do you think AB Inbev uses beech wood strips in a lattice pile at the bottom of their tanks? Answer, it's to have more of the yeast in contact with the beer for conditioning and lagering.

 

[bwible]

Why do you think AB Inbev uses beech wood strips in a lattice pile at the bottom of their tanks? Answer, it's to have more of the yeast in contact with the beer for conditioning and lagering.

I thought it was for the “beechwood flavor.”

 

[Vale71]

I thought it was for the “beechwood flavor.”

Obviously. Without recirculation having yeast trapped in a fixed structure is hardly going to bring it in contact with the beer. That'd be like pulling the handbrake on your car to make it go faster...

 

[TheBluePhantom]

Then what is the point of the beechwood? If the beer can't get to the yeast, it can't get to the wood. And barrels would do little to nothing as well. Or we can accept there is some slow movement, this is not a fast process. (brownian motion perhaps?)

 

[Vale71]

Then what is the point of the beechwood? If the beer can't get to the yeast, it can't get to the wood. And barrels would do little to nothing as well. Or we can accept there is some slow movement, this is not a fast process. (brownian motion perhaps?)

Simple diffusion.

 

[hottpeper13]

It's called surface area. The more the faster.

 

[Nubiwan]

I thought it was for the “beechwood flavor.”

I love it. I'm surprised no one commented how awful their beer is, and how to avoid their practices as best we can. Yes, i know they sell a lot of beer. How many like Bud light please?