Phenolic fingerprints and quality assessment of three types of beer

The quality of three types of beer (dark, light and non-alcoholic) was assessed using high-performance thin-layer chromatography (HPTLC) combined with high-resolution mass spectrometry and chemometrics. An HPTLC separation of the polar beer components in the ethyl acetate extract was developed. The polar components were detected either by the in situ 2,2-diphenyl-1-pic-rylhydrazyl (DPPH*) assay or by derivatization with the Neu’s reagent, followed by the PEG solution. This directly allowed the visual comparison and evaluation of the phenolic/flavonoid or radical scavenging (antioxidative) beer profile. Although the three types of beer showed a very similar chemical HPTLC pattern, the signal intensities were different. Detected by the Neu’s reagent, the dark beer extracts contained a high amount of phenolic compounds, and the light beer extracts showed a moderate content, while the non-alcoholic beer extracts had the lowest phenolic content. The HPTLC–DPPH* assay confirmed the higher radical scavenging activity of dark beer extracts, if compared to light and non-alcoholic beer extracts. The most active bands with regard to the radical scavenging property were identified to be desdimethyl-octahydro-iso-cohumulone and iso-n/ad-humulone. The use of pattern recognition techniques showed a clear differentiation between dark and non-alcoholic beer extracts, while light beer extracts did overlap with both beer types. This HPTLC screening allowed the (1) direct comparison of beer samples/types via classification and pattern recognition, (2) the assessment of the beer quality with regard to its antioxidative potential, and (3) the reference to single components.