Evaluation of PDMS Based Extraction Techniques and GC-TOFMS for the Analysis of Off-flavor Chemicals in Beer


App Note 10/2006

Various techniques employing polydimethylsiloxane (PDMS) as an extraction medium prior to GC-TOFMS analysis were investigated to measure off-flavors in aged beer. The techniques included stir bar sorptive extraction (SBSE), headspace sorptive extraction (HSSE), purge-and-trap (P&T) and closed-loop-stripping (CLS). SBSE appeared to provide the most accurate quantitation and was capable of detecting the most odor-active compounds. The peak deconvolution capability of the Leco Pegasus TOFMS was found critical to the detection and accurate quantitation of key off-flavor chemicals. Compared to fresh control beer, increases in furfural, furfuryl ethyl ether, furyl hydroxymethyl ketone, 2,4-dodecadienal, (E,E), benzeneacetic acid ethyl ester, ß-damascenone and 3-pyridinecarboxylic acid ethyl ester (a.k.a. nicotinic acid ethyl ester) were observed in beer samples incubated 12 wks at 30°C and increases in dimethyl disulfide, dimethyltrisulfide and benzeneacetaldehyde occurred in beer exposed to sunlight for 8 hrs.