DEVELOPMENT OF A METHOD FOR THE DETERMINATION OF VOLATILE ORGANIC COMPOUNDS ASSOCIATED WITH BEER AGING

Abstract

A method for the extraction, identification and quantification of eleven specific volatile organic compounds (VOCs) associated with off-flavours and off-odours in two different types of beers were developed. For this purpose, purge and trap extraction in combination with thermal desorption gas chromatography coupled to a mass spectrometric detection (TD-GC-MS) were used. This method was used to determine: furfural, ethyl nicotinate, (E)-2-nonenal, ethyl lactate, isoamyl acetate, 2-methyl-1-propanol, dimethyl trisulphide, 2, 3-butanedione, limonene, (+) (-) α pinene, and 2, 3- pentanedione in “pilsner” and “India Pale Ale” (IPA) beer. The samples were collected in the local brewery and analysed for the presence of eleven VOCs using the developed method. The VOC measurements after accelerated ageing of the beer were compared. The mean concentrations of eleven VOCs were measured over a range of 1.8 ng/L – 214 ng/L. An increase in the concentration of VOCs was observed during the ageing treatment for most of the VOCs. All the VOC measurements were below the acceptable flavour threshold limits: except (E)-2 nonenal and DMTS in IPA, their acceptable flavour threshold values correspond to 30 ng/L and 10 ng/L, respectively.