Diacetyl Rest

[AbsoZed]

Hi, guys. I recently started fermenting a batch of St. Paul Porter using Wyeast 1187. With this particular yeast, they recommend a diacetyl rest of at least a week, I believe. I was planning on waiting until Saturday to bottle, but I'm not sure if I should. Active Primary has been done for about a week, my gravity has not changed from 1.021 in that time. What would you guys say is the best amount of time to wait for a diacetyl rest before bottling? Thanks!

 

[brewmeister13]

I don't have an answer as far as time goes, but instead I can offer a way to test whether or not you have the precursor for diacetyl. The precursor leads to diacetyl development once it oxidizes over time. To check for this prepare a hot water bath with water at about 150F and an ice bath. Take two samples in glass containers. Cover each with tin foil. Place one in the hot water bath and the other leave at room temp. After about 15 minutes remove the glass from the hot water bath and cool back down to room temperature in the ice bath. Now smell them. If the one that was heated an cooled now smells buttery you need a rest and more time on the yeast.

 

[BrewinBromanite]

Hi, guys. I recently started fermenting a batch of St. Paul Porter using Wyeast 1187. With this particular yeast, they recommend a diacetyl rest of at least a week, I believe. I was planning on waiting until Saturday to bottle, but I'm not sure if I should. Active Primary has been done for about a week, my gravity has not changed from 1.021 in that time. What would you guys say is the best amount of time to wait for a diacetyl rest before bottling? Thanks!

How long have you been fermenting? What temps have you maintained (beer temp - not ambient)?

If you've fermented initially in the low end, it probably wouldn't hurt to let it finish up for a few days at the higher end of the range, both to finish/clean up and to get that diacetyl rest. If you've fermented throughout at the higher end of the range, you may have already covered that.

 

[BigFloyd]

How long have you been fermenting? What temps have you maintained (beer temp - not ambient)?

If you've fermented initially in the low end, it probably wouldn't hurt to let it finish up for a few days at the higher end of the range, both to finish/clean up and to get that diacetyl rest. If you've fermented throughout at the higher end of the range, you may have already covered that.

+1. This is all very temperature-dependent.

The reason for the D-rest a few days at a higher temp is to allow the precursor (acetolactate I believe) of diacetyl an opportunity to convert to diacetyl that the yeast can then munch on it and turn it into some other compound (that I don't recall the name of) that you can't taste. When tasting a sample to try and detect acetolactate, you're not looking for the butter taste (unless you've heated it), but a sort of slick feeling in your mouth.

Some folks think that only lager yeasts present a diacetyl problem, but certain ale yeasts like 1187 (Ringwood) and 1968ESB are well-known for it.

 

[AbsoZed]

Thanks for the replies. I've been fermenting for 2.5 weeks at about 72-75 Farenheit. Might do that diacetyl test later as well.

 

[BrewinBromanite]

I don't have personal experience with this particular yeast, but if you've been at those temps for 2.5 week, a diacetyl rest probably isn't critical, as it may have already effectively occurred (please those with more experience chime in if I'm way off on this). But you're likely ok to bottle soon if your gravity is finished and stable. (I usually bottle at weeks 3 or 4, fwiw.)

 

[BigFloyd]

Thanks for the replies. I've been fermenting for 2.5 weeks at about 72-75 Farenheit. Might do that diacetyl test later as well.

At those temps, I'd be more concerned about off-flavors other than diacetyl.

If you had run it at 64-65*F to ferment, you'd want to bump it up to 70-73*F a few days for the d-rest. It sounds like you've already been there for a while.

 

[AbsoZed]

At those temps, I'd be more concerned about off-flavors other than diacetyl.

If you had run it at 64-65*F to ferment, you'd want to bump it up to 70-73*F a few days for the d-rest. It sounds like you've already been there for a while.

I'd be more concerned about off-flavor, but for some reason, I have a lot of faith in this brew, ha.

It shall be bottled soon, then. Thanks for the input, guys.