Diacetyl rest below optimal yeast temp?

Hey guys,
I've got an ale going at about 66* and have hit my FG but the yeast is still working away. I've dropped the temp down to about 62* to slow the yeast up. The question is, will the yeast still clean up the diacetyl if operating under its optimal range?

Generally speaking cooling while fermenting is a bad idea. Should hold steady or slightly raise temp at end of fermentation for cleanest profile. Normal practice would be to raise temp a bit at the end to help in cleanup. Lowering temp may result in them not cleaning house as they normally would. What beer/yeast are you fermenting?

I'm with you on that, but in this case I'm trying to hit a specific gravity. If I continue to let it ferment, especially raise the temp, I'm going to overshoot.

dalime said:

I'm with you on that, but in this case I'm trying to hit a specific gravity. If I continue to let it ferment, especially raise the temp, I'm going to overshoot.

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Yes, but what are you going to do then? Keep it cool and then keg it and keep it under 40 degrees at all times so it doesn't start fermenting again?

I'd look at why your beer will go too low in the FG, but not try to stop it. I'd just let it go this time and adjust the recipe for a specific FG next time.

Are you an all grain or extract brewer. Some specifics on your process will help for the future but you need to let those yeastie beasties quit naturally or your likely to not like the result.

makomachine said:

Are you an all grain or extract brewer. Some specifics on your process will help for the future but you need to let those yeastie beasties quit naturally or your likely to not like the result.

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All grain. And I usually just let them do what they want, but in this case I'm trying to refine a recipe and was wondering if this was possible. Judging by the replies, the answer is no.

You should let it go and do exactly as you had stated, "refine" the recipe to hit your desired gravity. It's not a good idea to halt the yeast mid fermentation.

Does the beer even have any diacetyl? Using an ale yeast at 66 makes me kinda doubt that it's gonna be an issue. And even if you want to a d rest for an ale, it just consists of letting the fermentation go longer. So, I'd bet you don't have any diacetyl to worry about, and if you do, leaving it at 62 for a week or so will take care of it.

Denny said:

Does the beer even have any diacetyl?

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Mildly, but I was more curious as to whether you would get any cleanup out of the yeast while trying to stall it a bit. I just switched over to White Labs so I'm unfamiliar with the habits of their yeast. My second revision of this brew finished out way too low despite all my handy Beersmith calculations.

dalime said:

Mildly, but I was more curious as to whether you would get any cleanup out of the yeast while trying to stall it a bit. I just switched over to White Labs so I'm unfamiliar with the habits of their yeast. My second revision of this brew finished out way too low despite all my handy Beersmith calculations.

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For that problem, unless there was something way off with the ingredients in your recipe, you should focus on your mash temperature profile. Running too low a mash temp will definitely push the resulting brew towards the thin side. Might want to check the accuracy of whatever thermometer you use for monitoring your mash, because if it's reading 4-5 degrees high that could swing everything towards the dry side...

Cheers!