N. RETTBERG (1), M. Pueschel (1), L. A. Garbe (1); (1) VLB Berlin, Berlin, Germany

Analytical
Friday, June 6 - 2:00 p.m.-3:45 p.m.
Level 4, Red Lacquer Ballroom

For ages lipids in raw materials, intermediate products, and beer have attracted the attention of practical brewers and brewing researchers. Fatty acids influence yeast propagation and fermentation, flavor and foam stability, and might be involved in beer gushing. The vast majority of brewing-relevant publications dealing with lipids focus on free fatty acids, disregarding the occurrence of esterified fatty acids in beer. Over a period of three years (starting 2011) we established, optimized, and miniaturized sample preparation procedures for free and oxygenated fatty acids and introduced a straightforward assay to determine total lipids in wort, yeast, and beer. More than one hundred beer and wort samples from brewing sites across the world, as well as from pilot plants, were analyzed. Lipid concentrations deviated strongly between beer types and styles, as well as between brews. Within this work multitude challenges emerged, and some analytical details crystalized to be of special importance for reproducible and meaningful lipid analysis. The current paper summarizes general challenges in lipid analysis; analytical aspects connected to the complexity and wide polarity range of lipids in beer; and extraction and derivatization techniques suitable for lipid analysis in brewing. The current paper contains experimental data for free and esterified fatty acids from pilot plant beers and commercial brews and beers brewed with alternative starch sources. Additional considerations include the power of robust flame ionization detection; the necessity for mass spectrometry in special applications; the occurrence of odd chain fatty acids in bacteria infected beers; and the application of LC-UV or LC-MS equipment for targeted lipid analysis.

Nils Rettberg (born in 1983) is a trained brewer and maltster, holding a diploma in biotechnology/brewing science from the Berlin Institute of Technology (TUB). Since 2011 Nils is a Ph.D. student at the TUB Chair of Bioanalytics, coincidently he is employed in the VLB Department for Special Analyses. At TUB his work includes courses for students of biotechnology and brewing science, ranging from the basics of chemical-technical analysis to the application of sophisticated modern analytical techniques. At VLB Nils is involved in several research projects dealing with the analysis of raw materials, beer, food, and associated biotechnological products. Nils’ scientific focus is on beer and beverage analysis using mass spectrometry in combination with a stable isotope dilution technique. Initiated by his diploma thesis on “Flavour Active Epoxydecenals from Lipid Oxidation” he developed a deep interest in hop aroma, (oxygenated) lipids, and carbonyls—in short, those molecules that make beer either terribly good or horribly stale.