Diacetyl rest temperatures

[Phil Mud]

Hi Guys,

 

I just bottled an APA yesterday that, much to my dismay, had acquired a strong banana smell. I thought I'd bottle anyway, because you never know, but I think it's going to be undrinkable.

 

I fermented this brew with Wyeast 1272 (American Ale II) at 18C-19C for about 8 days - after this the FG was about 1.010 and I decided to let the temp come up to ambient temps for a D-rest. At this point the beer smelled and tasted great. I kept an eye on the temps and they got up as high as 26C - I didn't think this was a problem as the yeast had pretty much finished attenuating. Having said that I can't see how else the esters could have been produced in the last few days in the FV.

 

I had thought the start of attenuation was where these flavour precursors were usually formed - anyone else had this happen? What's the upper temp people allow for a D-Rest? I read somewhere the other day that D-rests should actually be at fermentation temps or lower for ales, and that it's just lagers that should come up. Thoughts?

[Kearnage]

I don't understand why you would do a D-rest for an ale, and why you would do a D-rest with any beer if you haven't noticed any diacetyl?

I sometimes bring my ales up from 18 to 20 odd possibly to make sure fermentation is done, but mainly for superstitious reasons.

 

I can't see any benefit from going as high as 26 deg after fermentation has finished.

[Phil Mud]

I don't understand why you would do a D-rest for an ale, and why you would do a D-rest with any beer if you haven't noticed any diacetyl?

 

I can't see any benefit from going as high as 26 deg after fermentation has finished.

 

woops, I might be misusing the term - I realise diacetyl is a specific flavour precursor, but thought that "D-rest" was often used as a bit of a catch all term to describe the yeast "cleaning up after themselves" - That's all I really meant and it seems from this forum and others like that's a pretty common thing to do with ales.

 

Is it correct that this usually involves upping the temperature to encourage the yeast to do this more aggressively? I didn't intend to bring it up to 26C, that was just the ambient temperature, however I wasn't too worried because I was under the impression that at that late stage of fermentation, off flavours were not a likely result - the LHBS guy who sold me the yeast certainly said this.

 

Kearnage, sounds like you keep the temps pretty low the whole way through - presumably your beer clears up well? My temp control is all about ice blocks, so it's high maintenance, but seems like it might be worth icing the whole way through.

 

[Kearnage]

OK, I see what you mean. Yes, a lot of brewers leave the beer for a few days to a week or so after FG is reached to let everything settle and the yeast to munch whatever else it can. This can be done at the ferment temp or raised a degree or two. I can see if you are using iceblocks that would be painful!

Even doing that my beer at bottling is never perfectly clear - that happens with secondary fermentation, storage, and refrigeration.

I grew up drinking Coopers Ale, so perfectly clear beer has always meant West End to me [sick]

 

If you have to work so hard for temp control, it might be best to not have such a long wait after FG is reached.