Diacetyl & My First All-Grain Batch

Things weren’t looking good for my first all-grain batch. I didn’t have a mash ton for a start. I’m not going to try and explain how much of a failure the 6-hour-long brew day was, and I’m not going to bore you all with the details about how I covered my kitchen in spent grain and sticky wort, but suffice to say things didn’t go to plan and I ended up with more beer on the floor than in the fermenter.

What I do want to talk about though, is the heavy butter taste that my beer has half way through fermentation. It tastes like butter popcorn and buttered bread – not a great taste in a 2% pale ale!

After some research online, I discovered that this buttery taste was caused by the chemical Diacetyl. According to Wikipedia, Diacetyl is a main flavour component in Butter. At low levels, diacetyl contributes a slipperiness to the feel of the alcoholic beverage in the mouth. As levels increase, it imparts a buttery or butterscotch flavor. Diacetyl is produced by the yeast as they turn the sugars into alcohol.

Once I knew what was causing this buttery off-taste in my beer, I needed to find out how to get rid of it. After searching through www.homebrewtalk.com forums I found that the most common advice for fixing diacetyl flavours was to bring the beer to a slightly warmer temperature for a few days after Primary fermentation is complete. This supposedly gives the yeast a chance to ‘clean up’ after themselves by reabsorbing the Diacetyl and other waste products before falling into the yeast cake. This is called a ‘Diacetyl Rest’.

Does it work? I don’t know yet. I’ve got a few days left of primary fermentation, so we’ll be doing a test here – I’ll seperate a small amount of the wort after primary fermentation. I will bottle the small amount of wort and try a diacetyl rest with the main batch of wort. I’ll post back in a week or so with my initial findings! If you have any tips for removing the diacetyl’s buttery taste, please leave me a comment!

Happy Brewing (and Happy Easter!),


4 responses to “Diacetyl & My First All-Grain Batch

  1. Nice post. My first all grain was crazy as well. Just keep at it!

    As for Diacetyl Rest, it absolutely is required. Far too many people rack to a secondary too early following the 1-2-3 rule. I’ve actually dropped secondaries all together because of diacetly off flavors and had great results. I generally leave my beer in the primary for 2 – 4 weeks then rack to a keg. Beer taste much better and theres less dishes. Diacetyl gone! Cheers and happy brewing.

  2. Great post. Definitely agree with the Diacetyl Rest. Just raise the temp of the brew to about 75 deg. F for a few days.

    homebrewtalk.com is absolutely great, and has a vast amount of information on home brewing.

  3. Henry,
    It is probably more important to consider ‘why’ you have the diacetyl flavor accuring in your beer. The typical cause of Vicinal Diketones (diacetyl being just one of them) is high fermentation temperatures. If you can ferment in cool temperatures then the diacetyl rest is not necessary. Having said that, it is important that the beer remain on the yeast for at least a week for the yeast to have time to ‘clean’ or eliminate any of flavors that are the result of the fermentation process.

  4. Henry Carless

    Thanks for the advice Max and Buglermcd! Unfortunately the diacetyl rest did not help even nearly enough. It removed a large amountof the buttery taste but not even close to the amount needed; I am beginning to think that the buttery taste may have been due to infection.

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