Diacetyl rest timing, is it ever (within reason) too late?

[whoaru99]

Say I miss typically suggested timing to start diacetyl rest and the beer goes to FG.

Is it too late to bother with diacetyl rest or is it still clearly beneficial, albeit not optimal?

 

[Gavin C]

Is it too late to bother with diacetyl rest ?

No

Is it ...still clearly beneficial?

Depending on the beer and your fermentation profile it may be beneficial.

Is it not optimal?

That depends on what your beer's requirements are. There are ways to minimize the need for a diacetyl rest. Prevention being the best form of cure.

Also a warm dacetyl rest is not required. Lager yeast will continue to metabolize unwanted fermentation byproducts even at cold lagering temperatures. The process is slower but will still occur given the right conditions (time and cold temperatures). Traditional lager fermentation profiles do not involve a warm dacetyl rest temperature.

TL,DR version. It's not too late, it may benefit your beer and is less than ideal ramping temperatures once FG is reached.

 

[BigFloyd]

It's best to do it when the beer is at 75% between OG and expected FG (while there still some yeast activity going on), but better late than never.

 

[whoaru99]

Therein lies part of the issue. I have an aversion to opening the fermenter for any reason not expressly necessary. So, I'm just sort of guessing when it's time to rest based on a noticeable slowdown of fermentation activity.

In this specific case it's a 1.071 Maibock I'm brewing. Pitched a good starter of WPL833 on Saturday afternoon and it took off within several hours. Now, the krausen is starting to fall and the airlock activity is quite slow (temp of fermenter has been 50F).

 

[BridgewaterBrewer]

I used to wait until the yeast were done before doing Diacetyl rest but I sometimes had issues with Diacetyl so I researched it and saw that some people start ramping the temp up once the activity is noticeably slower, say 75% done. It makes intuitive sense that the yeast might clean up Diacetyl precursors faster or better if you increase temp before they fall asleep but on the other hand maybe they'll make a cleaner beer if you let them finish eating the sugars before ramping up the temp. I haven't made enough lagers to be sure whether or not it has helped and I've never seen good data regarding which is the best approach. Having said that, lately I've been ramping temp up from 50 to 65 over a period of a few days, starting when beer is 75% of the the way to final gravity.