here - the 34th European Brewery Convention

1 Lodz University of Technology, Institute of Fermentation Technology and Microbiology, Lodz, Poland
The quality of a beer brand should be consistent, despite its production in different localizations. The
antioxidant potential of the beer brand produced in different breweries was evaluated. Since this brand
was produced as pasteurized and non-pasteurized beer, the influence of pasteurization process on
the antioxidant activity of beer was also assessed. Moreover, antioxidant properties of the products
after their storage at 22°C for 4 weeks were examined. The antioxidant capacity of beer was
measured both by the ferric reducing antioxidant power (FRAP) assay and the radical scavenging
assay (DPPH). The antioxidant activity of the beer brand showed significant differences depending on
its origin. When DPPH assay was used a significant decrease in the antioxidant activity of nonpasteurized
beer was observed after storage. Furthermore, the changes in antioxidant properties of
oat and barley beer were compared. A lower antioxidant potential was measured in the product from
oat.
P16a
Radical scavenging ability of protein and peptide thiols in beer
Marianne Lund 1 , Natália E.C. de Almeida 2 , Daniel R Cardoso 2 , Mogens L Andersen 1
1 University of Copenhagen, Department of Food Science, Frederiksberg C, Denmark, 2 University of
São Paulo, Chemistry Institute, São Carlos, Brazil
The antioxidative capacity of thiol-containing peptides and proteins (P-SH) in beer was evaluated by a
kinetic study of their ability to scavenge the 1-hydroxyethyl radical (HER), which is known to be the
main radical species formed during beer aging processes. A number of P-SHs was investigated,
among which were glutathione and LTP1 (Lipid Transfer Protein 1), an abundant beer protein. The
reactivity of the P-SHs towards HER was evaluated using a competitive kinetic approach, employing
the spin-trap POBN as a probe and by using Electron Paramagnetic Resonance (EPR) to detect the
HER-POBN spin adduct.
All investigated P-SHs were very reactive towards HER with apparent second-order rate constants
close to the diffusion limit and ranging from 0.5 to 6.1 10 9 L mol -1 s -1 with LTP1 having the highest rate
constant. The rates of scavenging HER by P-SH are competitive with the degradation of hops bitter
acids in beer and likely to protect against oxidation mediated by HER.
P17
The use of confocal laser scanning microscope (CLSM) for determination of filtration inhibiting
substances in kieselguhr and membrane filtration
Michael Kupetz 1 , Martin Zarnkow 1 , Thomas Becker 1
1 TUM Weihenstephan, Lehrstuhl für Brau- und Getränketechnologie, Freising, Germany
The filtration process of beer is enormously influenced by reversible and irreversible blockages. The
aim of this research is to stain and identify these components by CLSM. Staining components were
used which only react with specific beer ingredients. The filtration was performed on an automated
laboratory membrane, as well as kieselguhr precoat filter. A combination of the dyes propidiumiodide,
fuchsine-acid and schiff´s reagent made it possible to distinguish polysaccharides (α-/β-glucans),
proteins and yeast cells. The staining was performed by filtration of the dyes through the sample.
Conclusions of the particles could take on the basis of the available wavelengths of the lasers. These
allowed identifying the blockages of the surface layer and the interior of the filter medium.