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Impact of Fatty Acids and Medium Chain Fatty Acid Ethyl Esters on the Beer Crossflow Membrane Filtration
M. Kupetz, M. Weber, H. Kollmannsberger, B. Sacher and T. Becker

Membrane filtration represents a difficult process due to complex beer composition and its interactions with filter materials. Therefore, influences of fatty acids in general and medium chain fatty acid (MCFA) ethyl esters on crossflow membrane filtration have been investigated. During crossflow filtration trials, transmembrane pressure (TMP) rise as well as filterability were examined in laboratory scale. In an additional step, beer samples were mixed with MCFA ethyl esters or antifoam agent containing high amounts of fatty acids, resulting in an average decreasing filterability of 20% as well as a faster pressure rise in crossflow membrane filtration. A significant correlation (r = 0.99, P < 0.05) between TMP-rise and filterability using PES-membranes could be observed. Beer analysis revealed high decrease of β-glucan (up to 150mg/l) during the first filtration hour. The fluorometric β-glucan method showed a weak correlation to TMP increase (r = 0.77), whereas colorimetric method exhibited a more distinct connection (r = 0.93). Furthermore, the amount of 3-Methylbutyl acetate underwent only slight changes in reference and fatty acid enriched samples, whereas the content in MCFA ethyl ester spiked beer decreased up to 40%. In addition, content of Ethyl octanoate (30 %) and Ethyl decanoate (4060%) dropped during filtration in all samples. The observed results allow specific conclusions regarding filtration performance of beer in crossflow membrane filtration.

Descriptors: β-Glucan; filterability; Esser-test; volatiles; viscosity

BrewingScience - Monatsschrift fr Brauwissenschaft, 68 (September/October 2015), pp. 122-129