M-44: A novel gas chromatographic system to characterize volatile components in beer and its ingredients

A. TIPLER (1); (1) PerkinElmer, Shelton, CT, U.S.A.

Sensory
Saturday, June 7 - 1:00 p.m.-2:45 p.m.
Level 3, Crystal Room

Aroma plays a very important part in the flavor of many of the things we ingest—including beer. Most brewers use skilled and experienced beer tasters to monitor the organoleptic character of beer and help to ensure the high quality of their product. While this approach is usually effective, such tasting is highly subjective and would be greatly complemented by the availability of objective analytical data. A gas chromatograph system has been developed to assist in the objective characterization of beer aroma. This system can be used for the quality control of hops and adjuncts prior to brewing and to troubleshoot beer after production. A wide variety of hops types has been examined using this system, including American West Coast strains, English strains, and Noble strains. A range of beers has also been examined. The system can also be used to detect and monitor the presence of flavor defects such as dimethyl sulfide (vegetative), diacetyl (butterscotch), acetaldehyde (green apple), mercaptans (skunky) and t-2-nonenal (stale cardboard). The first component of this system is an equilibrium headspace sampler with an integral adsorbent trap. A hop or beer sample is placed in a sealed vial and maintained at an elevated temperature for a fixed period of time. During this time, volatile organic compounds (VOCs) from the sample migrate into the vapor (headspace) phase inside the vial. This vapor is then vented into a cooled adsorbent trap to focus and concentrate the VOCs. The VOCs in the trap are thermally desorbed and delivered to a gas chromatograph (GC) for component separation. The use of such a trap enables more VOCs to be collected and delivered to the gas chromatograph, thus increasing detection limits significantly. The chromatograph column used for the separation is a 60 m × 0.32 mm × 0.5 µm Carbowax column (same stationary phase as used in ASBC Method Hops-17). The effluent from the column is split between a mass spectrometer (MS) and an olfactory port (OP). The splitting device is fabricated using chemically deactivated laser-etched micro-channel wafer technology to ensure minimum dispersion and adsorption of compounds eluting from the GC column. The MS system enables the detection, identification, and quantification of each VOC component. The MS used in this work is a new single quadrupole designed specifically for GC use and has an enhanced sensitivity to enable spectral identification of VOCs at very low levels. The OP is a new design that enables the operator to smell each component as it elutes from the GC column in relative comfort. In this way, the chemical profiles generated by the MS may be correlated against the subjective organoleptic information obtained from the OP. This presentation will describe the design and application of this system.

Andrew Tipler is the chromatography research and technology manager at PerkinElmer in Shelton, CT. He is English, obtained a degree in pure chemistry at the University of Manchester, and worked for many years in various laboratories in England. Since joining PerkinElmer at their English site in 1983, he has been involved in the development and application of nearly all the company’s gas chromatography (GC) products. He moved to the company’s site in the United States in 1993 and continued to work on new GC technology and applications. He has been granted more than 30 patents and has given papers at many key GC conferences around the world. He is currently responsible for a team of highly skilled and knowledgeable scientists involved in identification and exploitation of modern technology and techniques to enhance our GC product line. He is also a keen home brewer and has won awards in regional competitions—particularly for English bitters. He is also a beer judge in the BJCP program.

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