O-21. The 20% solution for consistent beer quality

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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