R. M. ORTIZ (1); (1) MillerCoors, Milwaukee, WI, U.S.A.
Poster
Unambiguous identification and quantification of certain aldehydes in
packaged beer measured at low- to sub-ppb levels is challenging due to
the vast number of compounds that can interfere with the measurement of
the target aldehydes. This difficulty in resolution has hindered the
quantitation and subsequent connection with the sensory data. Successful
techniques to overcome the challenges of sensitivity and selectivity
have been established, particularly utilizing SPME-GC/electron
ionization (EI) MS, derivatization with O-2,3,4,5,6-(pentafluorobenzyl)
hydroxylamine hydrochloride (PFBHA), and selected ion monitoring (SIM)
at m/z 181. This work builds on earlier methods using this technique to
improve both sensitivity and selectivity. Resolution improvement can be
achieved by operating the mass spectrometer in the negative chemical
ionization (NCI) mode, as opposed to the EI mode: first, by taking
advantage of the derivatization reagent PFBHA, which serves to magnify
the signal intensity by virtue of the five fluorine atoms accepting the
electrons produced from the interaction of the ion filament and the
reagent gas methane. This is classified as the electron capture
mechanism, often referred to as high-pressure electron-capture mass
spectrometry (HPECMS) and is responsible for the increased sensitivity
compared to operating in EI mode. Second, the production of
characteristic fragment ions inherent to NCI mode results in improved
selectivity of the target aldehydes. This is especially useful when
attempting to measure aldehydes at the sub-ppb levels. Even at these
levels, many aldehydes can impart significant undesirable flavor
characteristics. Other aldehydes provide information related to the
specific degradation reactions and metric levels surrounding fresh beer
profiles. Changes in the levels of these selected aldehydes during
controlled storage conditions over time can be used to improve brewing
practice’s, make better comparisons with flavor characteristics, and
assess ingredient/contact material changes. As an example of this
technique and improved analytical method, a fresh batch of lager beer
was profiled at selected times over a 17 week period, and changes in
target aldehydes were reported.
Roman Ortiz received a B.S. degree in chemistry from California State
Polytechnic University in Pomona. He began employment with Miller
Brewing Company (now MillerCoors) in 2000 as a quality assurance
technician in the production laboratory of the Irwindale, CA, brewery.
In 2006 he was promoted to chemist for the analytical laboratory in the
Technical Center; in August 2013 he was promoted to senior chemist. He
has also served as an ASBC Technical Subcommittee chair (2010–2011).
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