Presenter: Constanze Ruff, Technische Universität Berlin,
Institute of Food Technology and Food Chemistry, Chair of
Brewing Science, Berlin, Germany
Coauthors: Thomas Kunz, and Frank-Jürgen Methner, Technische
Universität Berlin, Institute of Food Technology and
Food Chemistry, Chair of Brewing Science, Berlin, Germany
The origin of beer off flavors caused by oxidation has been
attributed to the formation of specific aging compounds. The
formation mechanisms, as different they are, mostly involve
reactive oxygen species (ROS), highlighting the importance
of intercepting oxygen reactions in the beer matrices or avoid
oxygen entry during the brewing process and storage. The
aim of this study was to figure out the different influences of
oxygen entry and oxygen entry inhibition using active packaging
material in the crown cap compared to the antioxidative
activity of SO2 addition on the formation of aging indicators
during storage. In this correlation also the combined application
of active packaging material and SO2 addition on oxidative
stability was investigated. Could the well-tried SO2 addition
obtain the best results or is it possible to offer brewers new
knowledge to improve beer flavor stability? Previous investigations
have shown that techniques combining EPR spectroscopy
and ascertainment of specific aging compounds as oxygen
indicators via GC-MS can be used to investigate the influences
of SO2 addition and different crown liners with O2-scavenger
properties on oxidative beer stability. The results after addition
of oxygen to fresh beer samples verifies that the formation and
increase in aging compounds is accelerated over storage time.
In summary, the inhibition of oxidative processes by adequate
SO2 addition in combination with after filling O2-scavenger
material in the crown liner is the best way to increase oxidative
beer stability during storage. However, the achievable increase
in oxidative stability using different crown liner materials is
strongly dependent on O2-scavenger properties. The compound
with the lowest O2-scavenger properties showed an effect only
after a longer storage time by the inhibition of oxygen diffusion
through the crown cap and wasn’t able to compensate for the
advantage effect of SO2 addition at 6 mg/L on oxidative stability.
The best O2 scavenger acted directly after filling, as well as
during storage, and was able to compensate for SO2 addition at
higher than 6 mg/L. A remarkable and, for the mechanism, important
point is that a comparable increase in oxidative stability
with SO2 addition or O2 scavenger leads to a different positive
effect on the formation of aging compounds during storage.
In this connection with use of O2-active packing materials, a
stronger reaction inhibition in the generation of specific aging
compounds (oxygen indicators) was detectable. Altogether this
research offers brewers useful further knowledge about how to
proceed to increase oxidative beer stability through SO2 addition
and/or active packaging material.
Constanze Ruff started her scientific career by participating
in chemistry summer school at the Freie Universität Berlin
before graduating. After school she interned for three months
at Herbstreith & Fox Company in Neuenbürg, Germany. She
then began studies in chemistry at the Freie Universität Berlin.
In March 2011 she switched to TU Berlin to the Department
of Food Chemistry to complete her course of diploma studies
in food chemistry. At the moment she is working on her
pre-diploma (Studienarbeit). She began her research work
in November 2010 as a student research assistant at the
Technische Universität Berlin, Institute of Food Technology and
Food Chemistry, Chair of Brewing Science, where she works
on GC/MS detection of aging compounds and improvement of
oxidative beer flavor stability.
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