Analysis of Phenolic Compounds in Lager Beers of Different Origin: A Contribution to Potential Determination of the Authenticity of Czech Beer

Beer contains a wide range of polyphenolic compounds originating mainly from malt and hops. In this work newly modified on-line coupled HPLC-photodiode-array (PDA)-MS methods were used for analysis of characteristic phenolic compounds in several Czech lager beers, in comparison with some foreign lager beers. After optimization of column type, elution mode, and gradient steepness, chromatography was performed with a Restek Ultra Aqueous, C-18 (5 mu m, 250 mm x 4.6 mm) column at 30 A degrees C and gradient elution using an optimized linear gradient of aqueous acetonitrile acidified with 1% acetic acid, at a flow rate 0.4 mL min(-1). In total, 49 compounds were identified. Eleven individual compounds, predominantly malt phenolics (gallic acid, (-)-catechin, epicatechin, ferulic acid, chlorogenic acid, morin, rutin, quercetin, caempherol, naringenin, and luteolin) were quantified by use of two detection techniques: MS with electrospray ionization and UV detection. Compared with foreign beers, Czech beers contained higher levels of most of the phenolic compounds; specific distributions of individual compounds were also observed. Experimental PDA results for individual polyphenols were evaluated statistically by modified cluster analysis. Because of very tight covariance of the data a new procedure was devised for correlation analysis. The set of beers analyzed can be divided into four clusters closely related to the origin of the and the technology used. It seems that some of the flavonoids have potential use in beer authenticity analysis.