O-8
Investigations into development of an analytical fingerprint method for beer
semivolatile analysis. For a brewer to provide their customer with a consistent and defect-free
product, it would be ideal to monitor the concentrations of all chemical
compounds that constitute the beer, ensuring each batch is the same as the last.
Realistically, it is not practical to measure all chemical compounds in each
beer brewed, so what is frequently done is to measure a select number of
compounds which yield a chemical "fingerprint" of the particular liquid. Based
on the raw ingredients used, the brewing conditions applied and the yeast
utilized for fermentation, each beer should have a different "fingerprint."
Components selected are not necessarily the most appearance, aroma or flavour
active, but ones present in high enough concentration to make their
quantification fairly straightforward, with any major problems associated with
the liquid quality detected in changes in their concentrations and respective
ratios. The usefulness of performing such an analysis is to monitor product
consistency and quality when one is changing brewing ingredients and/or
instituting a process change or modification, rather than a daily quality
control check. This presentation will outline our research into the development
of an analytical fingerprint method for semivolatile analytes in finished beer
on a gas chromatograph, with special emphasis placed on investigating different
sample preparation techniques. The method is capable of quantifying twenty-one
different semivolatile compounds, including alcohols, diols, acids, esters and
ketones. Studied were liquid-liquid extraction with solvents of varying
polarity, solid phase extraction (SPE) with different bonded phases and solid
phase microextraction (SPME) with various fiber types. Capillary GC columns
spanning a variety of bonded phases were evaluated to maximize analyte
resolution. Each method variation was compared and evaluated under the following
criteria: ease of analysis, time per analyses, number of analytes detected, cost
per analysis and precision and reproducibility of the results. It was concluded
that liquid-liquid extraction with ethyl acetate followed by analyte separation
on a DB-Wax capillary column was the methodology of choice, based upon our
study.
David Maradyn received a B.Sc. in Chemistry in 1991 and a Ph.D. in Organic
Chemistry in 1996 from the University of Western Ontario, in London, Ontario,
Canada. He joined the Labatt Brewing Company as a Post Doctoral Fellow in 1995,
working in the Technology Development Department. Since October 1997, he has
been working as a Research Scientist at Labatt, with a focus on analytical
method development. David has served the ASBC as member and chairman of
technical subcommittees and is currently a member of the Technical
Committee.
DAVID J. MARADYN and Kristian Rogers. Labatt-Interbrew North America, London,
ON, Canada.