Development of a High-Resolution Beer Headspace Analysis Method

Abstract

Fabrication of the necessary hardware to develop a high-resolution headspace method for analysis of beer volatiles is described. Beer volatiles were entrapped and enriched on a porous polymer trap. The volatile compounds were transferred to a narrow-bore capillary column where cryogenic retrapping occurred before capillary gas chromatography (GC) analysis. High sensitivity was achieved by complete sample transfer. This was made possible by a four-way switching valve that allowed the transfer to be made with no sample splitting. Run-to-run reproducibility was high; the coefficient of variation for most peaks was less than 20%. The volatiles were monitored by GC/flame ionization detection (for an overall beer volatile profile), by GC/flame photometric detection (for sulfur-containing compounds), and by GC/ mass spectroscopy (for compound identification). Comparison of the volatile trapping efficiency of two porous polymers (Tenax GC and Porapak Q) showed that the Tenax GC was better for compounds of low volatility, and Porapak Q was better suited to the highly volatile components found in beer.