Flavour component analysis by HS-SPME/GC–MS and chemometric modeling to characterize Pilsner-style Lager craft beers

Abstract

An HS-SPME/GC–MS (Head Space-Solid Phase Micro Extraction/Gas Chromatography-Mass Spectrometry) method was developed and applied to 79 beers (craft and industrial products) selected among the most common brands of mass-produced beer to evaluate their flavour profile. 111 volatiles were identified in the samples. PLS-DA (Partial Least Squares-Discriminant Analysis) was used to classify beers according to their different production methods. Good classification results both in calibration and cross-validation were obtained enabling a good separation between beer categories with high prediction accuracy. In order to find a reduced number of volatiles which could be relevant to discriminate the two beer typologies, VIP (Variable Importance in Projection) scores were calculated; on the basis of these results it was possible to identify a panel of 13 substances contributing the most to the observed differentiation (2-Methylpropyl 2-methylpropanoate, 3-Methylbutyl acetate, 7-Methyl-3-methylideneocta-1,6-diene (β-Myrcene), 3-Methylbutan-1-ol, Ethyl hexanoate, Hexan-1-ol, 1,1-Dimethyl-4-methylenehexahydro-1H-cyclopenta[c]furan, Ethyl octanoate, 3,7-Dimethylocta-1,6-dien-3-ol (β-Linalool), Ethyl decanoate, 2-Phenylethyl acetate, 2-Phenylethanol, Octanoic acid). The aim was to characterize the craft beers to differentiate them from other competing and lower quality products. The proposed approach could be a useful tool to verify whether samples comply with the statements reported on label concerning production process set out by product specification, at the same time providing a more chemically-oriented definition of the peculiar characteristics of craft beers.