Analytical Session
Martina Gastl, Lehrstuhl für Brau- und Getränketechnologie, Freising, Germany
Co-author(s): Elisabeth Wiesen, Barth Innovations, Nürnberg, Germany;
Thomas Becker, Lehrstuhl für Brau- und Getränketechnologie, Freising,
Germany
ABSTRACT: Turbidity provides the consumer’s first visual
impression of beer quality. Consumers expect a filtered beer to be a
clear, bright, non-hazy product that remains so during its shelf life.
Hazy products are often regarded as defective and perhaps even
potentially harmful. Therefore, controlling haze formation is an
important problem in beer production. For breweries not only costs from
rejected turbid beers and therefore an “image problem” arise, but also
increased costs due to the higher use of filter aids have to be
considered. It is well known, that beer is a complex mixture of over 450
constituents. In addition, it contains macromolecules such as proteins,
nucleic acids, polysaccharides, and lipids. Proteins influence the
entire brewing process with regard to enzymes, which degrade starch,
beta-glucans, and proteins. Protein-protein linkages stabilize foam and
are responsible for the mouthfeel and flavor stability of beer. Together
with polyphenols, proteins are thought to cause haze formation. With
this complexity, problems in processability are as various as the
constituents. Several substances in beer are responsible for haze
formation. Organic compounds such as proteins, polyphenols, and
carbohydrates (alpha- and beta-glucans) are known to form haze. In
addition, inorganic particles such as filter aids and label residues can
cause increased turbidity. In the brewery it is necessary to have
methods not only to identify the haze, but also to determine the source
of the haze formation. A simple, reproducible, and low cost analysis
procedure that can be carried out with basic laboratory equipment
demonstrates that the source of haze particles in beer (raw material,
yeast, etc.) can easily be determined and technological factors during
the brewing process of haze formation can be monitored step by step.
This study presents an overview of several research studies (haze
formation and haze identification), as well as analytical methods for
haze formation, protein analysis, and haze identification, including
dyeing methods, microscopic analyses, and size exclusion chromatography.
Martina
Gastl apprenticed as a brewer and maltster from 1994 to 1996 in
Klosterbrauerei Andechs, Germany. She studied brewing and beverage
technology at the Technische Universität München-Weihenstephan, Germany.
She graduated as an engineer in 2002. From 2002 until 2006 she
completed her Ph.D. concerning the “Technological Influence on Lipid
Degradation in Terms of Improvement of Beer Flavor Stability.” She is
currently assistant professor and head of the laboratory, as well as the
raw material and beverage design research group, at the Lehrstuhl für
Brau- und Getränketechnologie in Weihenstephan. Since 2008 she has been
working on her post-doctoral lecture qualification. Her research
interests involve characterization and interaction of flavor active
taste and aroma compounds in cereal-based beverages influencing beverage
harmony.
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