BLBS102-c33 BLBS102-Simpson March 21, 2012 14:5 Trim: 276mm X 219mm Printer Name: Yet to Come
33 Biochemistry of Beer Fermentation 645Labatt Breweries (Interbrew, Canada) in collaboration with
the Department of Chemical and Biochemical Engineering at
the University of Western Ontario (Canada) developed a contin-
uous system usingκ-carrageenan immobilized yeast cells in an
airlift reactor (Mensour et al. 1995, 1996, 1997). Pilot scale re-
search showed that full attenuation was reached in 20–24 hours
with this system compared to 5–7 days for the traditional batch
fermentation. The flavor profile of the beer produced using ICT
was similar to the batch fermented beer.
Hartwell Lahti and VTT Research Institute (Finland) devel-
oped a primary fermentation system using ICT on a pilot scale
of 600 L/day (Kronl ̈of and Virkajarvi 1999). Woodchips were ̈
used as the carrier material that reduced the total investment cost
by one-third compared to more expensive carriers. The results
showed that fermentation and flavor formation were very simi-
lar compared to a traditional batch process, although the process
time was reduced to 40 hours.
Andersen et al. (1999) developed a new ICT process in which
the concentration of carbon dioxide is controlled in a fixed-bed
reactor in such a way that the CO 2 formed is kept dissolved and
is removed from the beer without foaming problems. DEAE-
cellulose was used as carrier material. High-gravity beer of ac-
ceptable quality has been fermented in 20 hours at a capacity
of 50 L/h.
A well-explored concept for main beer fermentation is the use
of a gas-lift bioreactor system (see Table 33.6). In this system,
mixing established by the circulation of liquid and solid phases,
provided high liquid circulation rates, low shear environment,
and good mass transfer properties (Siegel and Robinson 1992,
Vunjak-Novakovic et al. 1992, Chisti and Moo-Young 1993,
Baron et al. 1996). Additionally, they possess the following pos-
itive characteristics: high loadings of solids, simple construction,
low risk of contamination, easy adjustment and control of op-
erational parameters and simple capacity enlargement (Vunjak-
Novakovic et al. 1998). Various carrier materials for gas-lift
bioreactors have been studied to perform the main fermentation
(see Table 33.6).
The optimization of temperature, wort gravity, feed volume,
and wort composition seems to be an important tool for the
control of the flavor-active compounds formation in immobi-
lized beer fermentation systems (Verbelen et al. 2006, 2010,
Willaert and Nedovic 2006, Br ́anyik et al. 2008). Many re-
searchers have concluded thatthe optimization of aeration during
continuous fermentation is essential for the quality of the final
beer (Virkaj ̈arvi et al. 1999). Oxygen is needed for the forma-
tion of unsaturated fatty acids and sterols that needed for growth
(Depraetere et al. 2003). However, excess oxygen will lead to
low ester production but to excessive diacetyl, acetaldehyde, and
fusel alcohol formation (Okabe et al. 1992, Wackerbauer et al.
2003, Branyik et al. 2004). It is possible to adjust the flavor of ́
the produced beer by ensuring the adequate amount of dissolved
oxygen by sparging with a mixture of air, nitrogen, or carbon
dioxide (Kronlof and Linko 1992, Br ̈ anyik et al. 2004). How- ́
ever, it remains difficult to predict the right amount of oxygen
because the oxygen availability to the immobilized yeast cells
is dependent of external and internal mass transfer limitations
(Willaert and Baron 1996, Willaert et al. 2004).Also, the reactor design, the carrier, and yeast strain can have
a dominant effect on flavor formation (Cop et al. 1989, Linko,
et al. 1997, Smogrovicova and D ́ om ̈ eny 1999, Tata et al. 1999, ́
Virkaj ̈arvi and Pohjala 2000).ACKNOWLEDGMENTS
This work was supported by the Belgian Federal Science Pol-
icy Office and European Space Agency PRODEX program, the
Institute for the Promotion of Innovation by Science and Tech-
nology in Flanders (IWT), and the Research Council of the
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