C. A. BOULTON (1); (1) University of Nottingham, Loughborough, U.K.
Fermentation
Wednesday, June 4 - 10:00 a.m.-11:45 a.m.
Level 3, Crystal Room
The use of cylindroconical vessels for fermentation and conditioning
dates back to the latter years of the nineteenth century. Since that
time they have come to achieve a dominant status and are now the first
choice for most brewers. Apart from increases in size and improved
hygienic design their design and operation remains largely the same as
the earliest examples; however, for many brewers the fermentation
process carried out in them has undergone radical changes. In order to
maximize productivity it is common to use a combination of very large
batch sizes, elevated temperatures, and highly concentrated worts.
Cumulatively these factors can result in deleterious changes in yeast to
the extent that crop viabilities are reduced to unacceptable values
such that deficiencies in beer quality may be observed and the process
of serial re-pitching becomes compromised. Similarly, the use of very
low conditioning temperatures can mean that the relatively slow and
inefficient cooling obtained by external jackets places unnecessary
time-constraints on cycle times. These problems require addressing since
many brewers desire to achieve further productivity gains by moving the
parameters already mentioned to even more extreme values. For this to
happen it is inevitable that changes in current fermentation practices
must be introduced in order to alleviate yeast stress and to provide
consistent, predictable, and sustainable performance. It is likely that
these changes will require a combination of altered management and
vessel design. This paper reviews work performed by this and other
authors where it has been demonstrated that it is essential to actively
manage yeast dispersion in large vessels throughout fermentation in
order to ensure consistency and rapidity in the primary stages and later
for timely and predictable crop formation and removal. Discussion will
be focused on the use of an external continuous pumped loop system as a
method for managing yeast dispersion. Other applications of this system
that would allow more precise and cost-effective control of both
uni-tank and dedicated fermentation and conditioning vessel operations
are highlighted. Work is presented that shows how problematic aspects of
the management of very large fermentation vessels, such as prolonged
fill times, can be used to advantage to manipulate beer flavor
attributes such as volatile spectra. In order for further progress to be
made it is desirable to have a method of improved monitoring of
fermentation progress, preferably continuous and in-line and with an
output suitable for use as a basis of automatic control. Results of
trials performed using an in-line gravity sensor that fulfills these
needs and shows close correlation with discontinuous profiles based on
sampling and remote analysis are provided. The potential benefits that
might be gained by the use of additional in-line sensors are discussed.
Christopher Boulton obtained a degree in microbiology and doctorate
in biochemistry at the University of Hull. The latter involved an
investigation into the biochemistry of lipid accumulation in oleaginous
yeasts. After a number of post-doctoral fellowships at the same
establishment, in 1984, he was hired as a fermentation microbiologist in
the R&D Department of Bass Brewers. Since that time Christopher has
undertaken a variety of technical roles involving R&D brewing
process development and NPD within Bass Brewers and later Coors Brewers
in which he further developed an interest in studying brewing yeast and
fermentation. In 2006, Christopher was appointed special professor in
brewing science and in 2007 lecturer in brewing science at the
University of Nottingham. Christopher is the author of more than 70
original papers and review articles; coauthor with David Quain of Brewing Yeast and Fermentation and with Dennis Briggs, Peter Brookes, and Roger Stevens of Brewing Science and Practice; and author of An Encyclopaedia of Brewing. Christopher is a Fellow of the Institute of Brewing and of the Institute of Biology and chartered scientist.
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