Program Book - Master Brewers Association of the Americas

P-88
Wort boiling by batch rectification—Possibilities to really
reduce a needed evaporation
MARCUS HERTEL (1), Karl Sommer (1)
(1) TU München, Lehrstuhl für Maschinen- und Apparatekunde,
Freising, Germany
Today energy costs are very high with a tendency to rise. As about
2260 kJ are needed to evaporate one liter of wort, it is advantageous
to reduce the total-evaporation during the boiling of wort.
The needed total-evaporation to undershoot a required targetconcentration
in the cast out wort is a property of the solution
and is given by the vapor-liquid-equilibrium of unwanted flavors
in wort and the start-concentration in the kettle-up wort. Thus,
this total-evaporation cannot be reduced by existing wort boiling
systems, although this is often asserted. The only possibility to
reduce the needed overall evaporation is a fractional distillation/
rectification. Based on the basics of evaporation and rectification, a
new wort boiling system was constructed. In this new rectification
wort boiling system, a side stream of wort is constantly drawn from
the wort kettle and fed into a rectification column. This column
is connected to the kettle. Thus, the evaporating vapor and the
recirculating wort are in strong contact. In this way, unwanted
flavors are strongly enriched in the evaporating vapor. Because of
this, the discharged steam has a concentration of unwanted flavors
that is much higher than the one produced by normal boiling
systems. Test trials were performed with the new wort boiling system
and its evaporation efficiency (AE) was acquired. The results of the
measurements show that an equal reduction of unwanted flavors
is achieved with about 50% less overall evaporation then the one a
normal wort boiling system needs. The evaporation efficiency (AE)
is thus doubled. With this new wort boiling system it is now possible
to really reduce the needed overall evaporation at the batch process
stage of wort boiling. More then 50% (!) of the overall evaporation
can be reduced in comparison to the existing wort boiling systems
although the aroma profile of the resulting wort stays equal. If the
boiling time is also reduced, the resulting worts have a clearly lower
thermal stress and a better protein composition. The needed column
can be exchanged in nearly every existing wort boiling system. The
savings of energy and money are enormous.
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.
110
P-89
Process engineering fundamentals to remove ambiguity
within the scope of wort boiling
HEINZ DAUTH (1), Karl Sommer (1)
(1) Technische Universität München, Center of Life Sciences,
Weihenstephan, Germany
In modern times many assumptions about the boiling process and
especially about evaporation that are circulating in the brewing
community are erroneous. This partial lack of knowledge can be
found throughout the various groups of people involved in the
brewing process; brewmasters, as well as manufacturers of brewing
plant equipment. One of the main misconceptions is that the
efficiency of the evaporation of undesired flavors, such as dimethyl
sulfide (DMS), can be increased by creating a larger surface area of
the boiled wort. A larger surface area can only increase the velocity
of the evaporation but it cannot, on any account, decrease the overall
evaporation. The latter is given by the concentration of a flavor in
the wort before boiling, by the target concentration after boiling and
by the vapor liquid equilibrium (VLE) of the aroma compound in
wort. Another important misconception is that the wort matrix is so
complex that the VLE of flavors could differ in every wort and thus
cannot be generally described. In truth, the VLE of a flavor in wort
can be described as VLE of the same component in pure water. This is
due to the fact that flavors are present in wort in such small amounts
that each flavor molecule is only surrounded by water molecules
(infinite dilution). Thus flavors cannot interact among each other.
This is also valid for possible interactions of flavors with the other
solutes, especially sugars. Finally brewers do not distinguish between
the different types of evaporation, although the calcination of flavors
underlies different mechanisms at an atmospheric boiling of wort or
at a flash evaporation. The fact is that the highest enrichment of a
flavor in steam vapor, and thus the minimum required evaporation,
is reached by a normal atmospheric boiling procedure. The different
types of flash evaporations can only reduce this enrichment in the
steam and thus increase the necessary total evaporation time in
comparison to an atmospheric boiling of the same wort but not
vice versa. All these misconceptions show, that there is a huge lack
of knowledge of the process engineering essentials of the wort
boiling process in the brewing community. Therefore the process
engineering basics of a boiling process will be explained in detail.
This includes answers to the following questions: Why does a
liquid (wort) boil? What is a vapor liquid equilibrium? What is the
difference between atmospheric boiling and flash evaporation?
What are we talking about when we discuss various residue curves?
This basic knowledge enlarges the technological understanding in
the brewing community and helps to critically review perceptions
concerning wort boiling that have been taken for granted.
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.