Hildebrandt, J.1, Thoerner, S.1 and Rettberg, N.1, (1)VLB Berlin, Berlin, GERMANY
Poster
Bitterness is a primary quality attribute of many beer styles. Depending on the product type, a wide range of bitter acids is present in commercial beers. Whereas light lagers mainly contain iso-alpha-acid isomers and/or their light stable analogues, late- and dry-hopped beers are characterized by the presence of alpha-acids, beta-acids, as well as their oxidation products. To a certain extent, all of these compounds contribute to beer bitterness and affect head retention and flavor stability. All-in-all, the list of relevant compounds is steadily growing, leading to an increasing demand for suitable analytical tools. In research related to beer bitterness, liquid-chromatography coupled to mass-spectrometry (LC-MS/MS) has been extensively used. Assays to quantify individual sets of hop bitter acids, as well as to monitor certain transformation reactions have been published. For this, triple quadrupole mass spectrometers were used. In order to ensure sensitive and selective analysis these instruments were operated in multiple reaction monitoring (MRM) mode. The major drawback of triple quadrupole mass spectrometers is their limited capability for substance identification. This drawback can be eliminated by use of high-resolution (hybrid) mass spectrometers that enable superior performance in both, quantification and identification. The current paper summarizes the development and application of a LC-Q-TOF-MS–based method for quantitative analysis of alpha-acids, beta-acids, iso-alpha-acids, reduced iso-alpha-acids, humulinones, hulupones, xanthohumol and iso-xanthohumol. In addition to this targeted dilute and shoot assay, strategies for identification of bitter acid transformation products using high-resolution mass spectrometry are presented.
Nils Rettberg (born 1983) is a trained brewer and maltster, holding a diploma in biotechnology with a focus on brewing science from TU Berlin (Germany). Initiated by his diploma thesis on “Flavor Active Epoxydecenals from Lipid Oxidation” he developed a deep interest in the analysis of molecules that make beer taste either terribly good or horribly stale. From 2011 to 2014 Nils performed his doctoral thesis on “Comprehensive Analysis of Hop Secondary Metabolites.” Simultaneously, he was a research associate at TU Berlin (Chair of Bioanalytics) and VLB Berlin (Research Institute for Special Analyses), where he was involved in both research and teaching. In January 2015 Nils became head of the VLB Research Institute for Special Analysis. Since October 2015 Nils has been in charge of the VLB Research Institute for Instrumental Beer and Beverage Analysis.
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