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!),