Getting a dense yeast cake by long primary/conditioning fermentaion

[HighVoltageMan!]

After the sugar, or most of it, is used up, they'll start consuming some of the esters, alcohol precursors and other compounds that cause off flavors. That "clean-up" phase is extremely important in making beer that really is clean-tasting and doesn't have any off-flavors.

JA you absolutely correct that the yeast will clean up themselves and time is very important in the reduction of compounds produced during the fermentation. However, esters are not one of those compounds that are cleaned up. They are mostly the fruity flavors and beer and I, for the most part, hate them. I wish I could clean those up, but once they are in beer, that's it. Longer ageing will reduce their potency, but they never seem to go away. Lagers (especially fermented with Carlsberg yeasts) have the biggest problem with this. They have to be prevented by creating an environment that the yeast will produce very little or no esters at all during fermentation.

There are two main things that are cleaned up by the yeast, acetaldehyde (green apples) and the big gorilla in the room, diacetyl (butter). The common mistake is to pull the beer off the yeast to soon. The yeast should be allowed to remain in contact with the beer to allow the final formation of diacetyl so the yeast can metabolize it and to finish fermenting. Flavors are still being "finalized" by the yeast, even after final gravity is hit.

I didn't mean to be a dick, I just wanted to point that out so others could avoid the confusion that I had.

 

[Ozarks Mountain Brewery]

There are two main things that are cleaned up by the yeast, acetaldehyde (green apples) and the big gorilla in the room, diacetyl (butter). The common mistake is to pull the beer off the yeast to soon. The yeast should be allowed to remain in contact with the beer to allow the final formation of diacetyl so the yeast can metabolize it and to finish fermenting. Flavors are still being "finalized" by the yeast, even after final gravity is hit.

I started raising my fermentation vessel slowly to 75ish for 3 days right at the end , that helped a bunch on off flavors

 

[Nosybear]

good recipe of the yeast cake. Can you tell me that how much time fermentation process takes place?

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Primary fermentation is about a week but may vary depending on yeast strain, temperature, original oxygenation. You should always verify that the fermentation is complete using a hydrometer or refractometer - you aren't looking for the absolute specific gravity with the refractometer in this case, just to see if the gravity is still changing. Secondary is not technically fermentation: You are waiting for the beer to clarify. Again, this is highly dependent on the yeast strain you're using. Some drop out in a couple of days, some never drop out. The other thing happening in secondary is the yeast are to some degree cleaning up some of their fermentation by-products. Time makes better beer so don't rush this part.

 

[J A]

There are two main things that are cleaned up by the yeast, acetaldehyde (green apples) and the big gorilla in the room, diacetyl (butter). The common mistake is to pull the beer off the yeast to soon. The yeast should be allowed to remain in contact with the beer to allow the final formation of diacetyl so the yeast can metabolize it and to finish fermenting. Flavors are still being "finalized" by the yeast, even after final gravity is hit.

Agreed...as I mentioned originally "some" of the esters are cleaned up. Aside from acetaldehyde, I've had very distinct fruit flavors from ale yeasts diminish or disappear within a few days during the clean-up phase. Even the ones that remain seem to diminish over time, especially fruity notes from lager yeast. When I use a secondary (most often because I need my primary for another batch) I pull a bit of yeast with the wort so I can maintain contact with a reasonable mass of yeast.

 

[Beer_Pirate]

Agreed...as I mentioned originally "some" of the esters are cleaned up. Aside from acetaldehyde, I've had very distinct fruit flavors from ale yeasts diminish or disappear within a few days during the clean-up phase. Even the ones that remain seem to diminish over time, especially fruity notes from lager yeast. When I use a secondary (most often because I need my primary for another batch) I pull a bit of yeast with the wort so I can maintain contact with a reasonable mass of yeast.

May seem like semantics at this point, but those compounds are an aldehyde and a diketone, respectively. Either way, I've had my fair share of experiences with both of those and esters. I fermented a batch of strong ale with S-04 at a high temperature and it smelled like bananas even after months