The Blog for Women Who Brew Beer


Posted by Maggie on August 20, 2010

Here is a nice brief article on diacetyl in beer.  I like it mostly due to the molecule drawing.  Very nice.  The article describes a buttery aroma but it is also described as a ripe banana flavor.  It isn’t terrible but beers definitely have a fresher, crisper flavor with low diacetyl levels.

This is from:

Reducing Diacetyl levels in Beer

Diacetyl is a chemical bi-product produced by yeast during fermentation, it gives the beer a strong buttery aroma and taste which is almost always detrimental to the quality of the beer. For this reason, homebrewers try to ensure that their finished beer contains as little diacetyl as possible.

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 StructureDiacetyl 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:


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