Engineering Session
Roland Feilner, KRONES AG, Neutaubling - Germany
ABSTRACT: Wort stripping after wort boiling or the
whirlpool process is an efficient way to reduce the amount of unwanted
volatile substances, which are formed post-boil primarily during the
whirlpool rest period. The focus lies mainly on free dimethyl sulfide
(DMS) and volatile Strecker aldehydes and reduced fatty acids. Due to
high temperatures present in the whirlpool, reactions like degradation
of DMS precursor and aroma formation are maintained. Immediately before
cooling the wort stripping system evaporates newly formed DMS. Thus it
is not necessary to evaporate the total amount of undesired volatile
substances, because stripping is one more system in the process, which
can reduce these reaction products. A new kind of stripping system is
based on a specific evaporation process, which is based on the
desorption of volatile substances without using primary energy. The
innovative design using a special inlet leads to the total covering of
the entire internal surface area of the stripping vessel by an even but
turbulent trickle film. Besides the generation of an efficient, uniform,
and turbulent layer, the stripping gas keeps up the driving gradient
between the gas and liquid phase. Based on this, the quantity of the
expelled substances is controlled via the stripping gas volume. To
evaluate the efficiency of evaporation, it is important to understand
the evaporation behavior of single unwanted aroma compounds under
reduced influencing parameters. Therefore the big matrix of wort is
reduced to pure water, and the temperature dependent volatilities of
these aroma compounds are determined. With this knowledge a basis for
the description of evaporation efficiency is generated. In the course of
this work, small-scale laboratory trials were verified by an upstream
pilot trial, where also the geometry and volume of the stripping gas of
the system was varied. While these investigations describe a
reproducible quantitative reduction of unwanted aroma compounds, further
investigations of this work are dealing with the rate of the reduction
reactions. Thereby correlations to the current dynamic parameters can be
arranged for further optimization of the brewhouse process. The
stripping gas control function of the new stripping system enables the
operator to react specifically based on the terms of malt quality like
DMS-precursor content and wort parameters at a very low energy level
combined with the same beer quality and an unchanged beer character. A
significant reduction in energy input with thermal treatment and a
simultaneously better wort quality could be realized. Reasons for this
are a highly efficient stripping process, which uses the existing
thermal energy of the wort instead of adding primary thermal energy.
Roland
Feilner (born in 1981) finished his apprenticeship as a brewer and
maltster. After that he studied food science technology in Weihenstephan
and graduated in 2006 as an engineer. His career entry with Krones AG,
Germany, started with membrane filtration of beer. At the same time, he
worked as a process and development engineer for thermal product
treatment. Additionally the degassing of beverages and juices was one of
his main development areas. Currently he is responsible for new
developments in wort treatment and process technology as a technical
specialist in the Krones R&D Division. Furthermore he has been a
post-graduate at the Technical University of Berlin since June 2011. His
area of research is the reduction of unwanted flavors in wort, with a
desorption-based stripping process.
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