Analysis of beer aroma using purge-and-trap sampling and gas chromatography

Abstract

Fingerprint profiles generated through GC analysis, are powerful tools for quality control in the food and beverage industry. Beer aroma profiles can be used for the fingerprinting of specific beer brands or for trouble shooting purposes such as the identification of off-flavours. The multichannel silicone rubber trap (MCT) lends itself perfectly to this task. The simplicity and robustness of the MCT makes it ideal for concentrating the volatile compounds that constitute the aroma of an alcoholic beverage such as beer. The retention of these substances by the silicone is based on dissolution into the polymer. This gives more intrinsic stability to the concentrated aroma compounds than traditionally used, adsorption based methods, so transport of the trap and contents should not be a problem. Thermal desorption is used to introduce the trapped aroma compounds to the chromatographic instrument. This eliminates the need for high purity solvents and greatly reduces the sample preparation time. The easily identifiable and stable background peaks from the silicone matrix makes the MCT ideal for repeated use with a thermal desorber. During this study the performance of the MCT as concentration device was investigated for its ability to concentrate aroma volatiles representing a wide range of volatilities. The sampling and desorption procedures were optimised in order to attain the required detection levels and repeatability of the analytical method based on this purge-and-trap sampling scheme