Note: I had originally wrote this post a week or so ago, but somehow it got deleted off of my site. Thanks to Google’s cache, I was able to retrieve it and get it back where it belongs.

In my first captivating posting about Diacetyl, I talked about what Diacetyl was how it provides a buttery flavor to everything it touches. I grippingly wrote on how Diacetyl can go through large swings in concentration as part of the normal brewing process. And you, my dear readers, held your breath as I described how the sudden appearance of strong buttery flavors in your aged beer can be a signal of bacterial contamination. I’m now taking this opportunity to describe a mechanism in which much smaller amounts, but still tasteable, amounts of Diacetyl can pop up in your beers while aging. That mechanism is through Maillard reactions.

Anyone who has watched as many “Good Eats” shows on the Food Network as I have has heard about Maillard reactions before. In the arenas of cooking and baking, Maillard reactions are extremely important. They are responsible for all of the yummy goodness that comes from the browning of food as the result of the application of heat. As it turns out, Maillards have a pretty important role in the aging of beer also, especially in the high alcohol speciality beers we all love.

A Maillard reaction is nothing more then a type of chemical reaction that occurs between a sugar and an amino acid. Beer has both sugars and aminos in varying amounts. Through a multi-stage reaction occuring right in your brew, various end molecules can be formed. The exact nature of these molecules is mostly dependent on what sugars and amino acids were involved with the process in the first place, but one of these possible end molecules is Diacetyl.

A study in which this phenomena was shown was published last July in Food Chemistry and titled “Aging characteristics of different beer types”. Researcher Bart Vanderhaegen and his colleagues at the Center for Malting and Brewing Science in Belgium aged eight beers of various characteristics for a year, and then tracked the changes in concentrations of various volatile chemicals throughout the year. All of the higher-alcohol beers they tracked showed increasing levels of diacetyl, increases big enough to be noticed by tasters. You can read the summary of this study or purchase the whole nine pages of it in it’s glory here.

So no need to worry about a slight buttery twang in your brew that wasn’t there a year ago. Just enjoy it and reflect on the cool science behind it.