Development of a stir bar sorptive extraction method to study different beer styles volatile profiles

A stir bar sorptive extraction method coupled to Gas Chromatography-Mass Spectrometry for the analysis of 52 volatile compounds in beer has been developed. The final optimized conditions were: 50 mL sample volume, 180 min extraction time, 25% (w/v) NaCl content and polydimethylsyloxane stir bars. Good values of linearity (R-2 > 0.99) were achieved for the calibration lines of all the compounds. The limits of detection and quantification obtained were low enough for the determination of the volatile compounds in the samples and the recovery values obtained for the majority of the compounds were between 80% and 120%. The precision of the method was also studied and acceptable values for this type of extraction technique were obtained ( < 20%). 30 samples of different styles of beers (ale, lager, stout and wheat) were analysed and their aromatic profile was characterised. Multivariate statistical techniques allowed the correct classification of the samples according to their volatile composition.