Ferment too high - Have I buggered it?

[losp]

I'm not going too well at the moment.

I put in the yeast last night (19:30) when i thought the thing was set to 12 (lager - wyeast 2308).
I realized at lunch time today that the temp probe was sitting right where the cold air comes out and the temp was playing up it was really about 18/19!! and had been sitting on this for 17 or so hours.

I fixed the thing now but how off is it likely to be? I'm going to put in a bloody fan tonight.

 

[mxd]

you may get a bit of D, check it, when it's down at the 80%-90% attenuated, if need be (I always do) put the temp back to 17-18 to let it finish off and clean up any D.

 

[losp]

you may get a bit of D, check it, when it's down at the 80%-90% attenuated, if need be (I always do) put the temp back to 17-18 to let it finish off and clean up any D.

Yeah I always do a D rest. i seem to get D sometimes even when the temp is bang on. If its just a bit of that ill be happy, but i am thinking i might have some funky yeast.

 

[cremmerson]

Ummmm... D? (Sorry, noob question).

 

[NewtownClown]

Diacetyl...

From John Palmer "How to Brew"

Diacetyl
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.

 

[losp]

Ummmm... D? (Sorry, noob question).

http://en.wikipedia.org/wiki/Diacetyl
Its a butterscotch-like flavor that is a byproduct of fermentation. In a Lager it stands out, whereas it might be OK in an Ale.

 

[Nick JD]

Another ketone that's similar to diacetyl that Manticle mentions occasionally is 2,3-pentanedione which has a "honey" flavour.

I am starting to think that where people taste a beer and describe it as diacetyly and "butterscotch" that the beer has both butter and honey. In a recent Pilsner, I get LOADS of honey, but no butter - whereas in the past I've had very buttery beers that have no sweetness assiciated with the butter that could be described as "werthers original" - more like the smell of a Hoyts Cinema foyer.

ED: since I've stopped using Czech yeasts to make German beers these ketones have both vanished. Mistreat a Czech yeast and it'll become a churning cow.