Program Book - Master Brewers Association of the Americas

P-90
Differences in the evaporation efficiency (AE) of common
wort boiling methods and their effects on the resulting wort
MARCUS HERTEL (1), Hans Scheuren (1), Karl Sommer (1)
(1) TU München, Lehrstuhl für Maschinen- und Apparatekunde,
Freising, Germany
An important function of the boiling of wort is the calcination
of flavors. If the total-evaporation is insufficient off-flavors will
occur in beer. Thus a brewer is anxious to have an adequate overall
evaporation. Brewers have recognized, that the efficiency of the
calcination of flavors differs in varying wort boiling systems. As
no one has an explanation for these differences, people in the
brewing section claimed that wort is too complex and that the
fluid mechanics in a boiling system cannot be clarified, so that this
efficiency could differ in every wort boiling system in any brewhouse
for each brew. (It is shown elsewhere that this is not true!) That is
the reason why total-evaporation is oversized in most breweries.
Because of this a dimensionless index was established, the so called
evaporation efficiency (AE). With this index every wort boiling
system can be characterized and classified. One disadvantage of
this method is that the AE has to be measured experimentally.
Because of this the different evaporation mechanisms that underlie
the different boiling systems were researched in this work. Based
on the basics of evaporation, residue-curves were established for
every common wort boiling system under different conditions
(temperature, pressure). These residue curves have been confirmed
with experimental decreasing values of flavors during wort boiling
in various boiling systems. It was possible to show that some boiling
systems perform a mixture of different types of evaporation. Thus
the decrease of a flavor component does not succeed the classical
type of residue curves. That could be the main reason why it was
misleadingly claimed that the calcination of compounds in wort
is too complex to be predicted. It is shown that the decrease of
different wort flavor components can be preeminently predicted
with the calculated residue curves for every common boiling system.
With these formulas it is now possible to predict the AE for every
wort boiling system under every condition. Thus an experimental
determination of the AE can now be avoided. It is now also possible
to predict a needed overall evaporation individually for every brew
in different boiling systems. An important result is, that the AE can
differ strongly with the different common boiling technologies.
Because of this the common boiling systems are suitable for the
calcinations of flavors in a different way. As a result all common
wort boiling technologies are classified based on their efficiency.
If the efficiency of a boiling system is known, it is much easier for
brewers to decide which boiling system is the most qualified for their
applications. Furthermore the efficiency of a wort boiling system
can differ under different conditions. Because of this, existing wort
boiling systems can be highly optimized if some parameters are
adjusted correctly. With this new knowledge this is now possible!
Marcus Hertel was born in 1975 in Nürnberg, Germany. Marcus
has been the director of the Hertel Brauvertrieb GmbH, Nürnberg/
Germany since 2006. Since 2007, he has been the director of the
Hertel GmbH Salzburg/Austria. Marcus has been a scientific
assistant at the Lehrstuhl für Maschinen- und Apparatekunde
(Chair Professor Karl Sommer) Technische Universität München,
Germany, since 2002. Marcus is active in basic research on the
steaming behavior and recreation kinetics of wort aroma compounds.
From 1996 to 2002, Marcus studied brewing science and beverage
technology at the Technische Universität München-Weihenstephan,
Germany, obtaining a Dipl.-Ing. degree. Since 2003 he has studied
business economics and economy engineering sciences at the
Fernuniversität, Hagen, Germany.
P-91
A new method to reduce the recreation of off-flavors during
the whirlpool rest
HEINZ DAUTH (1), Marcus Hertel (1), Karl Sommer (1)
(1) Technische Universität München, Center of Life Sciences,
Weihenstephan, Germany
A new approach is presented to reduce the content of undesired
flavors during the whirlpool rest by increasing the vaporization rate.
In this case it is not the thermodynamic effect of evaporation that is
essential, but in fact the process of vaporescence. This is realized by
constantly evacuating the air above the wort in the whirlpool during
the whirlpool rest. With shortened boiling processes, the conversion
of precursors of undesired flavors is often insufficient. Thus, offflavors
are continuously produced even during the whirlpool rest
and cannot be reduced without an additional evaporation, even
with modern practices. The most important flavor in this context
is dimethyl sulfide (DMS). With the presented method an increase
in the vaporization rate is created by constantly evacuating the air
above the wort in the whirlpool. Test trials have been carried out in
a pilot-plant unit which was equipped with suitable mountings to
permanently exhaust the air above the wort during the whirlpool
rest. Thus, a comparison by gas chromatography between the
normal rested wort and the treated wort was conducted. Samples
were taken in triplicate at different times during the whirlpool
rest, to meet statistical requirements. For this, the wort was
analyzed before and after a whirlpool rest of 30 min., with and
without the new suction system. To show that the differences in the
resulting amounts of DMS are mainly caused by the increase of the
vaporescence, trials were also performed with DMS in pure water,
where no production of DMS can occur. The results demonstrate
that there is a significant effect of using suction equipment on the
content of DMS after the whirlpool rest. This is solely due to the
higher vaporescence. Because of the high saturated vapor pressure
of DMS in combination with its activity coefficient, the mass stream
of DMS can be significantly enhanced by permanently exhausting
the air above the wort during the whirlpool rest. This results in a
lower concentration of DMS in the wort after the whirlpool rest. The
influence on other components (e.g. the desirable hop component
linalool) is not significant, because of their lower vapor pressures
and activity coefficients. Shorter boiling times and a higher amount
of precursors did not influence the quality of the resulting wort while
using the investigated suction system. A patent has been assigned
based on these results.
Dr.-Ing. Heinz Dauth was born in 1964. Dauth graduated as an
engineer for food technology and biotechnology from the Technische
Universität München–Weihenstephan in 1993. Afterward Dauth
was appointed as a scientific researcher at the Chair of Process
Engineering (Prof. Dr.-Ing. K. Sommer) in Weihenstephan, TU
München. He completed his doctoral thesis in 1999 in the field of
mechanical process engineering. Since 2003, Dauth has been a
scientific assistant and university lecturer at the Chair of Process
Engineering (Prof. Sommer), TU München. His main research
interests are bulk solids technology, dispensing technology, process
engineering for specific problems in the food and beverage industries,
and the formation of foam and stability of bubbles under the
influence of different gases and mixtures of gases dissolved in the
liquid. He is also responsible for the industrial cooperation program
of the institute. Dauth is also working as an assistant professor at the
Weihenstephan University of Applied Sciences, lecturing on process
engineering.
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