The Great Bottle Opener Giveaway

Home Brew Forums > Home Brewing Beer > General Techniques > diacetyl?

Reply
 
LinkBack Thread Tools
Old 01-17-2008, 01:44 PM   #1
biohazzardbrewing
Feedback Score: 0 reviews
Recipes 
 
Join Date: Aug 2007
Posts: 18
Liked 1 Times on 1 Posts

Default diacetyl?

What is diacetyl?
What is a diacetyl rest?
Why do I have to do it?
How do you do it?

Thanks in advance.

__________________
biohazzardbrewing is offline
 
Reply With Quote Quick reply to this message
Old 01-17-2008, 01:49 PM   #2
Yooper
Ale's What Cures You!
HBT_ADMIN.png
Feedback Score: 0 reviews
 
Yooper's Avatar
Recipes 
 
Join Date: Jun 2006
Location: Upper Michigan
Posts: 60,044
Liked 4202 Times on 3059 Posts
Likes Given: 779

Default

From Howtobrew.com:

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.


You actually don't need a diacetyl rest unless you have diacetyl. This is more common in lagers that are pitched warm and then the temperature reduced for fermentation. If you're doing a lager and need to do a diacetyl rest, then when fermentation is about 75% finished, you raise the temperature to 65-68 degrees for about 48 hours so that the yeast can clean up any diacetyl. If you cold pitch your lagers, this usually isn't needed. I've only needed to do a diacetyl rest one time. It also depends on the yeast strain- some lager yeasts are notorious for producing diacetyl. Some don't.

__________________
Broken Leg Brewery
Giving beer a leg to stand on since 2006
Yooper is offline
 
Reply With Quote Quick reply to this message
Old 01-17-2008, 02:22 PM   #3
HP_Lovecraft
Feedback Score: 0 reviews
Recipes 
 
Join Date: Jan 2008
Posts: 197
Liked 3 Times on 3 Posts

Default

Quote:
If you're doing a lager and need to do a diacetyl rest, then when fermentation is about 75% finished, you raise the temperature to 65-68 degrees for about 48 hours
How do you know when it is 75% done?
For lagers, I've always done 2 weeks at 50 degrees, then 4 weeks at 35 degrees.

Near the end of the 2 week primary I'll warm up to room temp, for the rest, then racking.

But how do you know when the yeast has started to remove its diacetyl? As soon as the airlock stops bubbling?

nick
__________________
HP_Lovecraft is offline
 
Reply With Quote Quick reply to this message
Old 01-17-2008, 02:23 PM   #4
TexLaw
Here's Lookin' Atcha!
HBT_LIFETIMESUPPORTER.png
Feedback Score: 0 reviews
 
TexLaw's Avatar
Recipes 
 
Join Date: Sep 2007
Location: Houston, Texas
Posts: 3,695
Liked 24 Times on 23 Posts

Default

Use the gold standard. Smell and taste the beer.


TL

__________________
Beer is good for anything from hot dogs to heartache.

Drinking Frog Brewery, est. 1993
TexLaw is offline
 
Reply With Quote Quick reply to this message
Reply


Quick Reply
Message:
Options
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Another Q about diacetyl brad451 General Beer Discussion 7 03-12-2009 11:11 PM
What is Diacetyl? Beecho General Beer Discussion 15 01-21-2009 08:14 PM
Diacetyl Mike M General Techniques 7 12-23-2008 12:49 AM
Diacetyl AnOldUR General Techniques 3 05-22-2007 11:50 PM
Diacetyl Ban in CA... olllllo General Beer Discussion 8 05-12-2007 08:24 PM