Beer is one of the world´s oldest and most widely loved and enjoyed beverages. Do not let its age fool you; it is a complex mixture that includes carbohydrates, proteins, organic acids as well as a myriad of volatile compounds. Beer is not immune from the effects of time and chemistry. The taste degradation in beer is due to several chemical reactions such as oxidation, photochemical reactions due to light exposure and even those resulting from contamination by microbes.
Staleness in beer
During the aging process, changes in some of the volatile compounds lead to a stale taste, which is often described as “cardboard”-like. Two main compounds are responsible for development of the stale aroma:
(E)-2 -nonenal ß-Damascenone
(E)-2 -nonenal is considered to be one of the main determinants of beer staling. The oxidation of some of the unsaturated fatty acids in malt leads to the formation of this aldehyde. The stale aroma resulting from this aldehyde is concentration dependent.
ß -Damascenone is a flavor compound with pleasant, but intensive scent. It is often found in other “fruity” alcoholic beverages, but is not a desired component of fresh beer. Its increased presence is an indicator of beer deterioration.
The characteristic bitterness
The physiologically valuable constituents of hops also include humulones, also known as alpha acids, which are responsible for the characteristic bitter taste of beer. Heating in the brewing process converts the alpha acids into iso-alpha acids
Perhaps you are wondering what any of this has to do with high performance liquid chromatography.
A reverse phase C18 column (such as MACHEREY-NAGEL’s NUCLEOSIL® C18) used with UV detection allows for the simultaneous determination of (E)-2-nonenal and ß –Damascenone allowing for a fast and efficient detection of stale beer.
Why choose MACHEREY-NAGEL?
The isohumulones (iso-alpha acids) formed during the brewing process are structurally very similar and cannot always be separated well with conventional C18 HPLC columns. The NUCLEODUR C18 ISIS column was developed by MACHEREY-NAGEL specifically for the separation of molecules of similar polarity and separates e.g., more strongly via steric interactions.
Conclusion
While you are enjoying a fresh, cold, delicious beer on St. Patrick’s Day, take a moment to raise your glass to all the analytical chemists out there who helped make it that way with the help of HPLC.
Cheers!