Diacetyl Rest

[wsmith1625]

My Marzen finished fermenting at 1.013 and the sample had a butterscotch aftertaste which I attributed to diacetyl. I slowly raised the temperature from 50 to 62 and after a few days I still detected butterscotch. I raised it again to 68 and let it sit a few more days and I'm still getting butterscotch. How long does it typically take for the diacetyl to clear up? I thought a day or 2, but my samples tell me otherwise. I also detected some harsher flavors in this last sample. Is 68 too high a temp for a diacetyl rest with a lager yeast? I used WLP820 and it tasted very clean in the first 2 samples. Thanks.

 

[VikeMan]

I'd say a couple of days is usually sufficient, when needed. But if you're still tasting it, I would advise patience. And 68F is not too high for a D-Rest for lager yeasts.

One other thought... what was your grain bill? Sometimes caramel/crystal malts can come across as a little butterscotch-y.

 

[wsmith1625]

9# Munich Malt 8L
1# German Pilsner Malt
.25# Caramunich 1 35L

The first sample was slippery and buttery, definitely diacetyl. The second and 3rd sample were more of an aftertaste, but still a bit of butterscotch. Also, the 3rd sample seemed to have a lot of yeast, so that could have contributed to the new off flavor I detected. I'll let it ride at 68 a few more days and check again. I'm in no rush with this batch. I'm going to lager 3-4 weeks after I transfer to the keg.

 

[AZ Maverick]

The most common way to do a diacetyl rest is to start it before fermentation is complete (about 5 points or so before fermentation is finished).
That is how I do it anyway. I don't know what happens if you do a diacetyl rest after fermentation has finished.
Here is what one of my lager fermentation cycles looks like, including the diacetyl rest and final cold crash.
Note how I start the D-Rest before fermentation is complete.

 

[Dland]

I'd let it rest at D rest temp for a while, if in doubt. Good homebrew sometimes takes patience, lagers take even more.

What I do is check keg with pressure gauge. If pressure in keg is going up, even if very slowly, yeast is still likely cleaning up your brew. There is not much downside in keeping a brew in mid 60's F for a week or so to assure yeast has worked out all it can.

 

[wsmith1625]

The most common way to do a diacetyl rest is to start it before fermentation is complete (about 5 points or so before fermentation is finished).
That is how I do it anyway. I don't know what happens if you do a diacetyl rest after fermentation has finished.
Here is what one of my lager fermentation cycles looks like, including the diacetyl rest and final cold crash.
Note how I start the D-Rest before fermentation is complete.

View attachment 778843

Thanks and awesome graph. Is that from aTilt?

 

[AZ Maverick]

Thanks and awesome graph. Is that from aTilt?

Yes it is.
I have two tilt hydrometers and I absolutely love them!
I have calibrated them against my hydrometer and I find them very accurate.
They are especially handy for monitoring the SG when I'm making lagers.

 

[wsmith1625]

I've seen them go on sale and thought "one more thing to sanitize", but having that data looks amazing.

 

[schmurf]

Cleaning and sanitisation of a Tilt is a breeze, no problems there. The only issue I have with it is the difficulty to replace battery, especially on version 1. The rapt pill is better in that sense.