In fact beer constitutes a good source of polyphenols and was found in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort study to be the main dietary contributor to the intake of the antioxidant hydroxybenzoic acid.
Polyphenols in Beer
In order to characterize the full range of polyphenols found in beers, a recent study by Paola Quifer-Rada et al., was conducted using LC-Orbitrap accurate mass spectrometry and the results published in the journal, Food Chemistry. Commercial samples of lager, Pilsen, Märzenbier and non-alcoholic beer produced in Spain were degassed, dealcoholized and purified by solid phase extraction (SPE) for HPLC analysis using a Linear ion Trap Quadrupole (LTQ) Orbitrap mass spectrometer scanning at 30,000 resolution from m/z 100 to 1000, with data analysis using XCalibur software.
These authors tentatively identified forty-seven phenolic compounds in these beers based on accurate mass measurement with a low error (<1.1 mDa) and MS2 spectral data. The power of using HPLC combined with accurate mass spectrometric analysis is clearly demonstrated by the fact that seven of these phenolic compounds were identified for the first time in beer. The complexity of these polyphenols in beer is probably unsurprising from sources such as barley and hops, and the numerous chemical and enzymatic reactions which take place during extraction, boiling of the wort and the yeast fermentation process.
A number of different phenolic acids were identified including hydrophenylacetic acids for which beer, along with olives, cider and wine, is one of the major sources in European diets. Flavonoids (anthocyanidins, chalcones, flavanols, flavanones, flavonols, flavones and isoflavonoids) were found in abundance and are often attributed to some of the biological effects and health benefits associated with their consumption. Bitter acids were identified and are characteristic compounds of beer since they are synthesized in the lupulin glands of the hop plant and contribute to the characteristic taste of beer. Additionally, flavour-active volatile phenols, such as vanillin, acetovanillone, 4-vinylsyringol, 4-vinylguaiacol and 4-vinylphenol, were identified and these have been previously reported as occurring in beers. No differences in phenolic profiles were found among the four types of beer, except for Märzenbier, which lacked catechin-O-hexoside, indicating a typical phenolic pattern for beers.
Routine Beer Analysis and Authenticity
Whilst the powerful and sophisticated techniques mentioned above are required for full characterization and also in the increasingly popular interest area of beer authenticity (great blog post by my colleague on this topic “How Can I Be Sure My Beer Is Authentic?”) there are multiple and varied techniques employed in the industry for routine beer testing.
I recently read two great interviews SelectScience conducted with laboratory managers who explained some of the instruments and techniques they use and why it is important to the final product.
In both articles, Paul Taylor from Murphy and Sons, UK and Helmut Klein at Brau Union in Austria emphasize the importance of quality control using such techniques as HPLC, ICP-OES and the wonderfully named Beermaster which is an automated photometric analyzer.
As with other areas of food analysis, particularly with respect to food safety, identification techniques have advanced way ahead of our ability to interpret the results in terms of either health benefits or health risks. Whilst undoubtedly for the future work will continue unraveling and interpreting the complexity of beer, the best advice for the Oktoberfest is to continue to enjoy the 7.7 million liters of beer as part of a varied and balanced diet!
More Resources and Reading
If you enjoyed this post, here is a great and highly read post by one of my colleagues Who Put Butter in My Beer?
The popular and useful Beer Analysis Application Notebook is certainly worth checking out.
If beer analysis is of general interest, it will be worth bookmarking our dedicated webpage on Beer Testing Information.