At what point during fermentation is diacetyl most noticeable?

[kiwipen]

At what point during fermentation is diacetyl most noticeable? Does it show up in the beginning, the middle or just in the end?

 

[lumpher]

Depends: lager or ale? In lagers, it's there throughout the fermentation, but worst at the end. That's why the diacetyl rest is there, is to warm it up to around 68 so the yeast can reabsorb the diacetyl. Ales ferment at a temp where the yeast can reabsorb it throughout the process.

 

[odie]

good to know. I don't do many lagers so never knew.

 

[dmtaylor]

Diacetyl doesn't always make an appearance. If it does, it's in the middle and end of fermentation, and/or after the beer is bottled or kegged. Not to worry... it usually ages out in 3-4 weeks. At least it does with lager yeasts. I can't speak to the English yeasts where it is technically "allowed".

 

[Erik the Anglophile]

A tiny bit of diacetyl can be welcomed in English styles, not czech pilsner levels of it though.
Some yeasts can also start producing it again after priming, that's why I gave up wlp005, it tasted fine at bottling, than after the short refermentation after bottling it was a diacetyl bomb.