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Old 12-26-2008, 06:39 PM   #1
Oct 2008
, MI
Posts: 14

I read in last month's Brew Magazine about common issues with excessive diacetyl. They never stated what it was or what taste issues it causes?

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Old 12-26-2008, 06:49 PM   #2
Shonuff's Avatar
Feb 2008
Seattle, WA
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Diacetyl - Wikipedia, the free encyclopedia
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Old 12-26-2008, 06:51 PM   #3
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Jan 2007
Armpit of Dallas (Irving), TX
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It is a yest by-product, usually in lager yeasts, that gives a buttery or butterscotch flavor. Usually, it is not a problem if you keep it on the yeast long enough, and handle the yeast well (proper pitching rate and temp), and may never even be present. If you do detect it, a diacetyl rest will usually take care of the problem, that is letting the temp rise to the 60s for lagers and 70s for ales, at the tail end of fermentation. Taste you hydrometer samples for diacetyl, if you detect butter or butterscotch, do a D-rest, but I have never had a problem with it, and some people can't even taste it in the amounts that may be present in beer.

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Old 12-26-2008, 06:54 PM   #4
Oct 2008
, MI
Posts: 14

Thanks, I was just curious what it was.

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Old 12-26-2008, 07:06 PM   #5
Dec 2006
Doylestown, PA
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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.
How to Brew - By John Palmer - Common Off-Flavors

...wrong forum btw

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Old 12-26-2008, 07:19 PM   #6
Oct 2008
, MI
Posts: 14

I realized that after I posted and reposted in the right forum. Thanks

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Old 01-21-2009, 05:08 PM   #7
Jan 2009
Posts: 1

OSHA is seeking comments regards a proposed rule on Diacetyl. See below for details:


Occupational Safety and Health Administration

29 CFR Part 1910

[Docket No. OSHA-2008-0046]

RIN 1218-AC33

Occupational Exposure to Diacetyl and Food Flavorings Containing Diacetyl

AGENCY: Occupational Safety and Health Administration (OSHA), Department of Labor.

ACTION: Advance notice of proposed rulemaking.

SUMMARY: OSHA is requesting data, information, and comment on issues related to occupational exposure to diacetyl and food flavorings containing diacetyl, including current employee exposures to diacetyl; the relationship between exposure to diacetyl and the development of adverse health effects; exposure assessment and monitoring methods; exposure control methods; employee training; medical surveillance for adverse health effects related to diacetyl exposure; and other pertinent subjects. In this notice, OSHA intends the term "diacetyl and food flavorings containing diacetyl" to encompass other constituents of food flavorings containing diacetyl. In addition to information on diacetyl, OSHA seeks information on acetoin, acetaldehyde, acetic acid, furfural, and other compounds present in food flavorings that may cause or contribute to flavoring-related lung disease. The Agency is also interested in and seeks information about diacetyl present in substances other than food flavorings (e.g., naturally occurring diacetyl or diacetyl in fragrances) as well as substitutes used in place of diacetyl (e.g., diacetyl trimer). The information received in response to this document will assist the Agency in developing a proposed standard addressing occupational exposure to diacetyl and food flavorings containing diacetyl.

DATES: Comments must be submitted (postmarked, sent, or received) by April 21, 2009.

ADDRESSES: You may submit comments, identified by Docket No. OSHA-2008-0046, by any of the following methods:

Electronically: You may submit comments and attachments electronically at redirect, which is the Federal eRulemaking Portal. Follow the instructions online for submitting comments.

Fax: If your comments, including attachments, do not exceed 10 pages, you may fax them to the OSHA Docket Office at 202-693-1648.

Mail, hand delivery, express mail, messenger or courier service: You must submit three copies of your comments and attachments to the OSHA Docket Office, Docket No. OSHA-2008-0046, Room N-2625, U.S. Department of Labor, 200 Constitution Avenue, NW., Washington, DC 20210; telephone 202-693-2350 (TTY number 877-889-5627). Deliveries (hand, express mail, messenger or courier service) are accepted during the Department of Labor's and Docket Office's normal business hours, 8:15 a.m.-4:45 p.m., e.t.

Instructions: All submissions must include the Agency name and the OSHA docket number (Docket No. OSHA-2008-0046). Because of security-related procedures, submissions by regular mail may result in significant delay in their receipt. Please contact the OSHA Docket Office at the above address for information about security procedures for submitting comments by hand delivery, express delivery, and messenger or courier service.

All comments, including any personal information you provide, are placed in the public docket without change and may be made available online at redirect. Therefore, OSHA cautions you about submitting certain personal information, such as social security numbers and birthdates. For further information on submitting comments, see the "Public Participation" heading in the SUPPLEMENTARY INFORMATION section of this document.

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Old 01-21-2009, 06:41 PM   #8
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Sep 2008
Lakeland TN
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I had it BAD in an Amber Lager. That batch had a nice D rest, too.

I am pretty sure it was caused by contamination. It developed in the keg.

I made an ale starter and pitched it in the keg. Let it sit for three weeks at room temperature and 90% of the butter smell and taste was gone. That keg is just about to kick, now.

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Old 01-21-2009, 06:43 PM   #9
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This is a great thread on the simplest cure for it....

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Old 01-21-2009, 08:10 PM   #10
Oct 2007
Posts: 158

I don't want to beat a dead horse here, but if my ales are fermenting close to 60F I won't be likely to develop diacetyl, right? My house is pretty cold and my water bath usually hovers a shade over 60 and I've never tasted diacetyl over the past year that I've been brewing (either that or I have and don't know what it tastes like).

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