Diacetyl Rest for Ale's?

[jbsengineer]

I took a brewery tour this past weekend at Ithaca Brewing Company in Ithaca, New York. I naturally asked 100 questions and learned a couple techniques I had not heard of before. One of the more interesting things was that they ferment at 70 degrees (thought that was a little high) and that they do a diacetyl rest for all there Ale's. In my brewing knowledge I have never read anything about diacetyl rests for ales nor have I ever tasted diacetyl in my beer (I ferment at a strict 65).

Do you do diacetyl rests for your Ale's? If you do (or don't) what would that look like? Bring it up to 80 degrees after the primary phase?

Maybe they do the rests due to the 70 degree fermentation temperature?

Whatever they are doing makes some delicious beers!

 

[daksin]

British ale yeasts are notorious for throwing diacetyl, and many other oxygen-hungry strains will as well. I've found I don't need one as long as I ferment in the right temp range and give my high-flocculating yeasts plenty of oxygen.

Also, commercial fermentation under pressure in huge cylindro-conical fermenters is a very different beast than our little 5 gallon buckets, which with no pressure in the vessel thanks to the airlock, amounts to basically an open fermentation.

Pressure fermentation suppresses ester formation, and the warmer temperature may help counteract that, as well as shortening the turnaround time of the beers. The huge vertical pressure on the yeast also has some effects that may include excess diacetyl production. Even small amounts of diacetyl can lend a slickness to the mouthfeel of the beer, even if no butteriness is perceived, so they may do the diacetly rest to ensure the crispest mounthfeel for their beers.

Really, I have no idea why exactly they do it, as every fermentation setup and yeast strain is different, I just wanted to point out how very little their system has in common with what we're used to.

 

[jbsengineer]

That made perfect sense.

Guess some more research in these areas are needed!

Any idea what a diacetyl rest would look like for them?

 

[Yooper]

That made perfect sense.

Guess some more research in these areas are needed!

Any idea what a diacetyl rest would look like for them?

If you leave your beer in the fermenter for at least 3 days after the beer is finished, that's a diacetyl rest. That's part of the "clean up" process brewers are talking about and why most don't rack to a clearing vessel, or package the beer, until at least three days of the same FG reading. It ensures the beer is done, but the diacetyl rest happens for about 24 hours or so once FG is reached.

Often, I raise the temperature at the tail end of fermentation (about day 5) when using a yeast that tends to produce diacetyl, and to encourage lazy yeast strains to fully attenuate. I only raise about 3-5 degrees or so, but it's enough to encourage the yeast to keep going and to clean up the diacetyl.

 

[sweetcell]

i do a diacetyl rest for many of my ales, of a sort: as fermentation starts to slow down, i ramp up the temperature a few degrees. so if i'm fermenting at 68, i'll leave it there for 3-5 days until fermentation noticeably slows down (based on the churning visible through the carboy) then i'll ramp up over a few days until i get, say, 744 or 5 days later. this helps with both diacetyl and attenuation. i won't ramp up as much for thicker/sweeter beers like a stout.

 

[Hermit]

I also always raise the temp towards the end. Just think of it as a 'maturation' process. Lots of things happen and as far as I know, all good.

 

[daksin]

If my beer needs a diacetyl rest, I typically let it warm up to the (very warm) temperature of my room. I try to do this while there is at least some yeast activity going on (not yet at FG), otherwise the yeast get lazy. If you have really bad diacetyl in a finished beer, the only thing to do is to pitch a big starter at high krausen and let them work on the diacetyl as they finish the remaining sugars you pitched in.

 

[BigFloyd]

If you have the ability to do it, stepping an ale ferment (after the first week) from the low-mid 60's up to finish around 68*F is a good practice, especially for batches using a yeast strain known for producing diacetyl (like 1968 ESB for example).