Diacetyl prevention

[rustygates]

Just cracked my first homebrew yesterday and whatdaya know its a diacetyl bomb.. It is an APA so it kind of sticks out like a sore thumb.

I understand that warm fermentation can often lead to the buttery/butterscotch flavor but I'm pretty confident I kept the temp in check (68-70F). Also, I may have under pitched as well seeing as the lag time was over 2 days.

Questions:
-Could a slight fluctuation in temp. (68-70F) over the 2-3 weeks in the fermenter create this diacetyl off flavor?

-Looking back, I may have pitched at a high temp (78-80F). Could this produce a lot of diacetyl?

-Could it be from a long lag time due to under pitching?

-Can diacetyl be produced during bottle conditioning and will it fade over time?

 

[dmtaylor]

Strange things can happen. What yeast did you use? Was it an English yeast? Sometimes they throw some diacetyl. Could also possibly be due to contamination by wild yeast, unfortunately.

In any case, if you keep the bottles warm for another 2-3 weeks before chilling down, this can often help the residual yeast to eat the diacetyl, which serves as a food source for the yeast after they've eaten all the sugars available (like the priming sugar). If you cool down the bottles, they won't be as willing to eat the diacetyl. Think of it like a diacetyl rest inside the bottles, only it doesn't happen as fast and in my experience usually takes close to 3 weeks.

Coincidentally... I got some diacetyl in a marzen that I just bottled yesterday. This is of course far more common with lager yeasts (I used WLP830). I debated over whether to bulk age it in the fermenter or just to bottle it anyway and condition in the bottles, and decided on the latter option. So I won't pop any bottles for at least 2 weeks, maybe 3, in the hopes that it's gone or almost gone by then. It's worked for me in the past so I have high hopes.

 

[rustygates]

Huh, didn't realize a contamination could cause diacetyl. I figured it would be sour if contaminated but I guess that would make sense considering I frantically tried to cool a 5 gal full boil in the bathtub. Took over an hour to get it down to 80F with tons of stirring and I ran out of ice... (I have since bought a chiller)

I used 1450 Denny's Favorite which imagine it's an American strain but don't really know.

Thanks for the tip on letting them sit at room temp. Will definitely give it a shot.

 

[dmtaylor]

Ahhh....... Denny's yeast is a lager yeast. There you go. The diacetyl should fade in 2-3 weeks. Boom.

 

[rustygates]

Really? The wyeast description for 1450 has a ton of ales listed in styles. I did notice however that the temp range for Denny's is 60-70 and I was sitting on the top end of that.

 

[dmtaylor]

Actually after second-guessing myself, I'm not exactly sure. I recall now that it used to be called "2450" by Wyeast which would mean it was a lager strain, but now they changed the name to "1450" which is more of a hybrid strain. Only a microbiologist can tell for sure. I might be a scientist but I'm not a microbiologist. Let's just hope you don't have contamination. I doubt the ferm temperature or the slow chilling had anything to do with the diacetyl.

 

[rustygates]

Cool , well thanks for your input! Definitely going to let it sit regardless

 

[jddevinn]

Did you measure the 68-70°F as the air temp or the beer temp? If the air temp the beer could have been in the 80+°F range.

 

[rustygates]

I had the thermometer right against the carboy so hard to say. It definitely wasn't reading the internal temp.

 

[brewcat]

Get a fermometer if you don't have one.

 

[microbusbrewery]

I've never heard of wild yeast producing high levels of diacetyl; pediococcus will and the remedy is to pitch brettanomyces along with it (if you're intentionally souring) as brett will clean up the diacetyl. I think the more likely cause is stressed yeast and/or moving off the yeast cake too soon. Did you taste it before bottling? If not, in the future I would. From the online version of How to Brew:

Diacetyl is most often described as a butter or butterscotch flavor. Smell an unpopped bag of butter flavor microwave popcorn for a good example. It is desired to a degree in many ales, but in some styles (mainly lagers) and circumstances it is unwanted and may even take on rancid overtones. Diacetyl can be the result of the normal fermentation process or the result of a bacterial infection. Diacetyl is produced early in the fermentation cycle by the yeast and is gradually reassimilated towards the end of the fermentation. A brew that experiences a long lag time due to weak yeast or insufficient aeration will produce a lot of diacetyl before the main fermentation begins. In this case there is often more diacetyl than the yeast can consume at the end of fermentation and it can dominate the flavor of the beer.

 

[jddevinn]

Did you just pitch one package? What was the OG? Probably did underpitch and then the temps went up while the yeast were multiplying. Keeping them warm may cause it to age out...

 

[rustygates]

I tasted before bottling and really didn't detect any but wasn't really looking for it. I pitched one package into an OG of 1.051. Lag time was a bit long at approx. 36 hrs and I pitched before the wort had lowered to fermentation temp. I'm hoping that I can avoid this in the future by doing a yeast starter and getting the wort to temp. before pitching.

 

[liquidcourage]

If you pitched at 78-80 it very well could have produced off flavors. How long was it at 80 before you got it down to 68?

 

[rustygates]

[QUOTE How long was it at 80 before you got it down to 68?[/QUOTE]


Maybe a 2-3 hours. I was just stoked to have my first beer in the fermenter so not exactly sure.

 

[liquidcourage]

Like someone said get a Fermometer and put it on the side of your fermenter. 2-3 hours proa ly isn't a big deal but in the future wait til you're at the temp you want before you pitch.

 

[rustygates]

Can diacetyl be produced during bottle conditioning since there is some yeast activity and growth in the process?

 

[dmtaylor]

Can diacetyl be produced during bottle conditioning since there is some yeast activity and growth in the process?

Yes, definitely, absolutely. Extra time (2-3 weeks) at room temperature is usually all that is needed for the yeast to eat the diacetyl.

 

[rustygates]

Thanks, really appreciate all your help.