Presenter: Christof Reinhardt, 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
In a highly competitive market place quality and consistency
of beer have become of paramount importance. Besides beer
flavor, color, and foam stability, one major attribute of beer
quality is colloidal stability. If it comes to an undesirable haze
during beer storage, the product is classified by the consumer
as inedible. Although a variety of substances can be responsible
for colloidal instability and haze formation, the most frequent
and important form of non-biological haze formation has
been identified as the interaction of proteins and polyphenols
naturally occurring in beer. Our previous investigations have
shown that metallic ions like iron with specific oxidation steps
also have an important influence on the colloidal stability of
beer caused by their influence on complex formation with
protein-polyphenol compounds and oxidative stability. In order
to obtain high colloidal product stability for a long period,
it is necessary to remove the haze-active proteins and/or
polyphenols using technological measures during the brewing
process. Polyphenols are normally removed by nylon 66 or
PVPP, while proteins can be removed with the help of silica
gel or bentonite. In this correlation in the brewing industry it is
increasingly popular to use gallotannins, as a high molecular
weight tannic acid, to improve colloidal stability. When they are
used in the process before filtration, they react primarily with
haze-active acid SH-group containing proteins by adsorption
and precipitation. The protein complexes that are formed are
removed completely by filtration and are responsible for an
increase in colloidal stability. Complexes that involve metallic
ions like iron are also removed in this way. Consequently, a
deceleration of oxygen activation and radical generation by the
Fenton-Haber-Weiss reaction system is observable, resulting
in a further advantage for colloidal and flavor stability as
confirmed using EPR (EAP and T values), GC-MS (aging
comp.), and other analytical methods. Our studies have shown
that for the appropriate procedure (quantity, dosing point) the
application of gallotannins is a good tool to increase oxidative
and colloidal beer stability, resulting in lower formation of haze
and typical aging compounds during storage.
After apprenticing as a brewer and maltster at the Braugold
Brauerei Riebeck GmbH & Co. KG Erfurt (2004–2007),
Christof Reinhardt started his studies at the Technische
Universität Berlin in biotechnology with a concentration in
brewing technology (2008–2013). He began his research in
January 2011 as a student research assistant at the Technische
Universität Berlin, Institute of Food Technology and Food
Chemistry, Chair of Brewing Science. He is working on
determining the impact of fermentable and nonfermentable
carbohydrates and gallotannins on the flavor and oxidative and
colloidal stability of finished beer using EPR spectrometry.
