analysis of vicinal diketones in beerOn a recent visit to the local pub with some friends for our ritual of beverage testing, specifically beer, we had a strange encounter. When the drinks were taste tested, two of my friends commented on the buttery taste of their beer. And even though each of us was accused of playing a prank on the others and we all denied it, it certainly didn’t spoil a great evening.

Back at work, I searched through our online Fermentation page featuring numerous applications for beer (and wine) analysis, and talked to colleagues and found that the buttery taste comes from vicinal diketones, such as diacetyl (2,3-pentanedione) or 2,3-butanedione and they can be either naturally occurring or can be produced during the fermentation process in some alcoholic beverages and foods. The problem for a brewer is to know when the fermentation process is complete. This is usually done by closely monitoring the drop in gravity. If the beer is chilled and packaged too early it can trap a substantial amount of diacetyl in the beer since the yeast hasn’t been given enough time to reduce the diacetyl levels and thus is the cause of the buttery flavor in beer. Mystery solved!

While the nose is one of the trusted tools in the brewing industry when it comes to aroma and flavor, as a chromatographer, I started to look at modern separation and detection techniques that could help address this problem with science. And sure enough, I found that in 1999, the European Brewery Convention issued a method for the determination of 2,3-butanedione and 2,3-pentanedione in beers via headspace gas chromatography. I performed a quick literature search and came across a recently published method described in Application Note 10418, titled, Determining Vicinal Diketones in Beer Using Valve-and-Loop Headspace Analysis, (downloadable PDF) This method uses one of our latest gas chromatographs (Thermo Scientific TRACE 1310 Gas Chromatograph) equipped with an electron capture detector module and one of our headspace autosamplers to analyze these compounds. The 35 °C headspace oven temperature allows the analysis to be performed at nearly room temperature, matching the recommended temperature of the method without employing complex and expensive cryogenic devices or increasing the time between two successive analysis to allow the cooling of the system.

Another resource I found was a notebook on the topic, titled, Beer Analysis Applications Notebook (downloadable PDF) listed a range of detailed applications critical to the brewing industry with links to peer reviewed journal articles and, in my opinion, it will be an invaluable resource to any laboratory interested in the analysis of beer.

Additional Resources

Do check out the following on-demand videos on beer analysis in our Food and Beverage Webinar Library (both videos require filling out a short registration form):

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Have you ever experienced unusual tastes in your beverages? Let me know if there are any other applications you have come across which are critical to the brewing industry? I would like to hear your thoughts and experiences.