Forgot to D-rest my Schwarzbier

[Skyphoxx]

Noticed the bung in my shwarzbier was kinda sitting ontop of the carboy in the hole. Not snugly seated. I noticed this when cleaning one of my kegs. It had been 10 days and I didn't want to chance any more air getting in (if any had), so I racked it off the cake into a clean keg.

It hit me this morning that I didn't allow for a d-rest before raking off of the cake and into the keg which was purged of o2 and filled with co2.

What should I do? Forget the d-rest? Take the keg out of the keezer for a day or two then bleed off/refill the co2 every once in a while? Will the yeast in suspension blowoff the diecetyl if any exists? Luckilly it didn't look infected, nor did it smell off. Just wondering what I should do now without ruining a batch even further.

I used SafLager S-23 with a 1 liter starter.

 

[Yooper]

If you don't taste diacetyl or have an issue with the mouthfeel reminiscent of diacetyl (oily and slick), then it's fine!

 

[hunter_le five]

Yup, if it tastes fine, then it's fine.

D-rests are not at all mandatory. They are only truly necessary if any diacetyl actually formed during fermentation. Many brewers just do them as a matter of course as a precaution, not because they really need to.

 

[Skyphoxx]

Pulled a sample. Slicker than water for sure. Not much butter, but a hint.

 

[LandoLincoln]

We need to rename this "diacetyl purge."

"Diacetyl rest" makes no sense at all.

 

[Yooper]

Pulled a sample. Slicker than water for sure. Not much butter, but a hint.

You can try putting it at room temperature, but generally you need active yeast to clean up the diacetyl.

 

[Skyphoxx]

Ill just pretend then. Cant hurt right? Set keezer to 65 and will purge the keg and repressurize a few times a day until monday.

 

[biertourist]

It's not quite as simple as "if you don't taste diacetyl, you're good". Although you probably ARE good.

The problem is that the diacetyl precursor alpha-acetolactate can still be in your beer and you can't taste it, you transfer to keg and introduce oxygen and then that acetolactate converts into diacetyl and you get a new diacetyl spike in your beer that you CAN then taste and then you're probably without most of your yeast and at low temps where the yeast isn't going to be very quick about converting the daicetyl to acetoin downstream.


The best test is the "diacetyl force test" -take a sample of your beer and warm it up to room temperature or higher (I use a hot water bath aka my kitchen sink and get it up to 122F so the reaction is faster and then throw the sample in the freezer for a minute so I don't have to sample hot beer- the high temp will form diacetyl quickly) and splash it around a bit to introduce some oxygen; the oxygen plus the warmer temp will convert acetolactate to diacetyl so that you can taste it. NOW if you don't taste any diacetyl, you know you're good. The point is that a diacetyl taste test isn't valid unless you first warm the beer up for several minutes in the presence of oxygen (you need to convert the pre-cursors to diacetyl to ensure that you're past the point of diacetyl becoming an issue later.)


If you get diacetyl from the force test ("fail" the diacetyl force test), the fastest way to get rid of it is to take some of your yeast and make a starter / "krausen bier" and pitch this yeast at high krausen back to the main yeast. You can even use a speise calculator to determine how much to add to carbonate the beer nauturally. Pitching fresh yeast at high krausen to the beer at d-rest temps will get rid of diacetyl as quickly as possible. -The traditional German process involves adding 10% krausen beer, but you don't need to actually add that much for diacetyl reduction; we're not commercial breweries; we can just wait a bit longer.

Commercial breweries test their beers during fermentation for diacetyl and it's other "cousin", 2,3 Pentadione -together they're called vicinal diketones (VDK), for the presence of VDKs and simply leave the beer on the yeast / do a D-rest until the VDK levels drop below the thresholds that their quality assurance processes dictate. For homebrewers the equipment to do a VDK test is cost prohibitive so we can just do a diacetyl force test as a "poor man's" version.

minor geeky detail: 2,3 Pentadione generally isn't a concern as most yeast strains produce far less 2,3 Pentadione than 2,3 Butanedione (Diacetyl) AND the taste threshold for diacetyl is 10x higher; it just so happens that the equipment and process for testing for diacetyl actually measures both VDK chemicals as they are very similar.


Adam

 

[biertourist]

Bonus: PDF from Chris White (White Labs) on the diacetyl timeline: http://www.whitelabs.com/files/Diacetyl_Time_Line.pdf


He calls out that RedHook ESB typically has above the taste threshold of diacetyl as a part of it's flavor profile, which is pretty much a dead giveaway that they're using the Fuller's strain which is also famous for leaving diacetyl behind and obviously the only actual historical example of a British ESB. (Yes the BJCP created an entire "beer style" based upon a single beer from a single brewery; someone should tell them that a single beer does not a style make; even if it's an incredibly awesome beer.)


Adam

 

[Yooper]

One other thing to mention (and Adam's scientific explanation is awesome!) is that some people simply don't have the gene to taste diacetyl.

So even if you do the force test, you may want to have your wife or a friend taste as well. There are even some (very good!) BJCP judges that don't have the gene to taste diacetyl, and have to rely on another judge for that point at times.

So, my flippant 'if you don't taste it, it's fine' wasn't meant to be that flippant- but it's true that it's YOUR beer. If it tastes fine to you, then it is fine. If you don't detect diacetyl, and the beer is enjoyable, then the beer is still fine. I hope that makes sense!

 

[PGEduardo]

This happened to me on my first (and so far only) lager. I brewed a Dos XX Special Lager clone and skipped the D-rest before lagering for a month. Butter was overpowering so I just pulled it from the keezer and let it sit for a week or two at room temp and then chilled/carb'd. I didn't add any yeast and had already racked it into a keg from a secondary.

Worked great!

 

[Skyphoxx]

Did you bleed the keg at all during the process PGEduadro?

 

[VladOfTrub]

When diacetyl is noticed during primary fermentation, a diacetyl rest will work. If diacetyl forms during secondary fermentation or during the time it is in the keg, a diacetyl rest will only temporarily remove it. Diacetyl will form later on, even if the beer is krausened. Everything hinges on whether the diacetyl was formed in the primary or afterward.

When a diacetyl rest is performed, lager yeast is warmed to ale temps. The yeast cranks up, rapidly burning up fuel and nutrients, which will be needed later on to support yeast throughout the lagering phase. If the lager is going from the boiler to the belly in six or eight weeks, performing a diacetyl rest, whether it is needed or not, probably won't cause any issues. However, if a Maerzen or any type of lager that requires a lengthy lagering phase is brewed, and it is going to be aged out as it should be. The beer would need to have speise added and have to be krausened, as well.

It is better to improve the primary brewing process if diacetyl becomes a reocurring problem. At the least, follow the counsel on doing a diacetyl test, before beginning a diacetyl rest. The rest is only used in order to save a failed lager.

 

[PGEduardo]

Did you bleed the keg at all during the process PGEduadro?

I normally carb to 12 psi so I think I just let it hiss a tiny bit when I pulled it out so that any expansion wouldn't cause a leak. You certainly want to keep a good amount of clean CO2 in there. Depending on the volume of headspace, your corny keg can probably handle the pressure...