It is important to note that Diacetyl can also be produced by bacterial infection of the wort during fermentation, so the first step in reducing diacetyl levels in your beer is good sanitation.

Diacetyl Molecular Structure

Fortunately, diacetyl is reabsorbed by the yeast during the end of primary fermentation. This can only happen however at regular fermentation temperatures – If you are largering a beer, you will need to raise the temperature of the fermenting beer to room temperature for a few days after primary fermentation; this is called a diacetyl rest. If you are brewing an ale, your beer should be fermenting at the correct temperatures already; to reduce diacetyl levels simply leave the beer in primary fermentation until the buttery taste and aroma has subsided.

For more information about Diacetyl and how to get rid of it, check out these useful links:

http://beerme.com/diacetyl.php

http://en.wikipedia.org/wiki/Diacetyl
Thanks for reading,
Brewing Tips Staff.