Presenter: Alastair T. Pringle, Pringle-Scott LLC, St. Louis, MO
Producing a beer with consistent sensory and analytical
attributes is an important aspect of quality. For a new brewery
this can be a daunting task as there are a seemingly endless
number of items in the literature to measure and control. The
Pareto principle states that 80% of the effects come from
20% of the causes. Therefore, to make efficient use of their
resources brewers should identify and control those vital few
(20%) causes that result in the majority of the inconsistency.
One approach is to view the brewing process as a series of
inputs, processes, and outputs. Through this approach product
consistency can be achieved by controlling the inputs and a
few key factors in each of the brewery processes. Control of
the primary inputs to the overall process can be achieved by
accepting shipments based on certificates of analysis, sensory
analysis, and periodically auditing critical parameters. In the
case of individual brewery processes (brewhouse, fermentation,
conditioning, and finishing), each can be controlled by
identifying and controlling a few factors that have a major
effect on the important attributes of finished beer. Because
each process is separate, but interdependent, it is critical to
measure the outputs from individual processes. Fermentability,
free amino nitrogen, and bitterness are examples of wort
parameters that could be measured, as well as gravity, since
these parameters affect the performance of the next process
(fermentation) and the finished beer. The outputs of the
entire process are the analytical and sensory attributes of the
packaged beer, where the ultimate test of consistency is their
trueness-to-type.
Alastair Pringle earned undergraduate and graduate degrees
in microbiology. He joined Anheuser-Busch in 1984 following
five years of postdoctoral research. At Anheuser-Busch Alastair
held a number of technical management positions, including
director of brewing research, where his responsibilities
included all aspects of the brewing process. He is currently
the principal consultant at Pringle-Scott LLC, a science-based
consulting company that works with craft breweries on process
control and quality. In addition, Alastair teaches microbiology
at Maryville University in St. Louis, MO, and is a member of
the IBD Board of Examiners.
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