Diacetyl in a low FG beer

[Helloworld]

My latest brew has diacetyl. I am puzzled by this because my finishing gravity was 1.012. I use two phase temperature control.

I used White Labs 01 and set the controls to 67 F. After a week I saw the low gravity and transferred to secondary for a cold crash. Should I leave the beer in primary longer? Do ales need a diacetyl rest?

 

[yeastylad]

I'm not an expert and have only been brewing about a year myself, and my diacetyl experiences are mostly literature based only, but I don't think there is any reason why you couldn't have diacetyl in a low FG beer. Doing a cold crash after only a week could be a contributing factor though. You want to leave your beer at fermentation temperature even after you've reached terminal gravity for a while to give the yeast a chance to clean up any diacetyl if it is present. You've essentially put the brakes on any yeast activity after just a week. Even after active fermentation is done and final gravity has been achieved, it may seem like everything is done and dusted, but the yeast is still working away to clean up after itself, diacetyl and all.

I would raise back up to 67 and do a diacetyl rest, and see where that gets you. It sounds like you may have cold crashed too soon maybe.

 

[Helloworld]

The subject brew is already in the keg and carbonated, so I'm unable to help it; however, now I know to let subsequent brews sit for a while longer. I might even try bumping the temp up a degree or two after reaching terminal gravity to encourage the yeast to clean up. I'll have to do some research on that for ale yeasts.

 

[Yooper]

The subject brew is already in the keg and carbonated, so I'm unable to help it; however, now I know to let subsequent brews sit for a while longer. I might even try bumping the temp up a degree or two after reaching terminal gravity to encourage the yeast to clean up. I'll have to do some research on that for ale yeasts.

That sounds perfect! Normally, you'd bump the temperature up before FG is reached, though. Just about the time the beer is finishing up, while the yeast is slowing down with fermentation but still active, is the perfect time to bump up the temperature. If you're fermenting at, say, 62 degrees, when the activity slows down and the krausen starts to fall, you can bump it up to 68 degrees (as an example) to encourage the yeast to fully attenuate as well as clean up diacetyl.

 

[yeastylad]

I'm using that approach for the first time with my current batch - Off The Topper from Northern Brewer (Heady Topper clone apparently) which uses Yeast Bay's Vermont Ale yeast. They recommend fermenting at 67 and raising to 72 after 3 or 4 days. I don't have a point of reference, but I'm hoping for decent attenuation.

I hear in some cases diacetyl can fade over time if you keep the brew refrigerated, again, no point of reference except I read it had worked for others (I did a bit of research a few months back as I had a diacetyl concern of my own).

 

[ncbrewer]

That sounds perfect! Normally, you'd bump the temperature up before FG is reached, though. Just about the time the beer is finishing up, while the yeast is slowing down with fermentation but still active, is the perfect time to bump up the temperature. If you're fermenting at, say, 62 degrees, when the activity slows down and the krausen starts to fall, you can bump it up to 68 degrees (as an example) to encourage the yeast to fully attenuate as well as clean up diacetyl.

Since you didn't mention checking gravity, I guess it's safe to base this timing on kraeusen falling, and not taking any readings. Is this right?

 

[Helloworld]

Since you didn't mention checking gravity, I guess it's safe to base this timing on kraeusen falling, and not taking any readings. Is this right?

Next time I do this I'll probably take some readings. That being said, I have a Speidel fermenter with a handy spigot to do so. If I was using a carboy I might just eyeball it.