G. S. DERDELINCKX (1), S. M. Deckers (2), D. Santiago Riverros (3),
J. Titze (4), J. Rodriguez (5), C. Schoenberger (6); (1) KULeuven-FBIW-M²S-Hydrophobin Chair 2, Heverlee, Belgium; (2) Brasserie d’Orval, Florenville, Belgium; (3) KULeuven-FBIW-M²S-LFoRCe-LIBR,
Heverlee, Belgium; (4) Döhler, Nieder-Olm, Germany; (5) University of
Madrid, Madrid, Spain; (6) Joh. Barth - Hop Academy, Nuremberg, Germany
Quality
Wednesday, June 4 - 1:00 p.m.-2:45 p.m.
Level 3, Crystal Room
The causes of primary gushing are better understood thanks to methodical
study of the problem and to efficient cooperation between brewing
researchers and scientists involved in exact disciplines. This active
co-working has enabled the presentation of an up-to-date view of each
step of primary gushing supported by a theoretical comment. Indeed, it
is demonstrated that “primary gushing” is a complex mechanism and
consists of successive steps based on chemical properties, physical
laws, and thermodynamic equilibriums. Primary gushing of beer requires a
minimal concentration of CLASS 2 hydrophobins (critical crystallization
concentration), a minimal carbon dioxide concentration (carbon dioxide
content of beer), and typical surface properties of the container
(hydrophilic surface = glass surface). At every step, minimal conditions
are needed to allow to go over to the next one, and finally, if all
conditions are fulfilled the beer can overfoam due to fluid expulsion.
In fact, after formation of the nanobombs in the glass bottle, their
explosion at bottle decapping, the quantity of carbon dioxide (gaseous
and bond) released depends on temperature, essentially pointing out the
role played by hydrogen bonds between carbon dioxide and water molecules
in this model. Nevertheless, at the start of formation of carbon
dioxide bubbles requires nucleation sites and energy; in the case of
primary gushing it is suggested that this energy is provided by the
existence of throbbing bubbles and consecutive collapse that provokes
cavitation and liberation of the carbon dioxide bond into the beer as it
arises when the bottle head is knocked. We will present by a
communication based on “exact science” the essential and minimal
“environmental beer conditions” that induce “primary gushing,” as well
as the several steps where curative actions can be taken in order to
reduce the risk and even prevent primary gushing.
Guy Derdelinckx (born 1954) has been active at KULeuven since 1994 in
the field of the applied microbiology of the brewery and as the Chair
of Brewing Microbiology. He developed research in the fields of bottle
fermentation, spontaneous fermentation, and Brettanomyces/Dekkera
sp. characterization. Recently, together with a small research group,
he developed research in the field of primary gushing in order to
unravel the “missing piece of the puzzle of primary gushing” (citation
L. Winkelmann). This allowed them, by tackling several aspects of exact
science, to detail by a model supported by theoretical comments, to
detail the different steps of primary gushing. This work was carried out
in the frame of the GTF (Gushing Task Force) created under the
initiative of CS; the aim of this group is to help brewers to solve
their primary gushing problems—everybody is welcome to join this group.
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