Determination of several flavours in beer with headspace sampling–gas chromatography

In order to determine flavours (diacetyl, pentanedione, acetoin and acetaldehyde) in beer, gas chromatography coupled with headspace sampling technique was developed in our laboratory. The calibrations were accomplished by six level standard addition methods, and relative coefficients were ⩾0.999. Repeatability experiments were accomplished by detecting 20 successive same standard samples, which showed that detection precision was <2% relative standard deviation (RSD) for three flavours (diacetyl, pentanedione and acetaldehyde), and detection precision of acetoin was <2.5% (RSD). Four flavours gradually increased and then decreased during the process of fermentation, and they leveled off when the fermentation was over. The ratio (diacetyl/pentanedione) reflected the degree of contamination: normal beer had a ratio of approximate 1; the ratio (diacetyl/pentanedione) was higher than 1, displaying that beer was contaminated by microbes. Our data suggested that gas chromatography coupled with headspace sampling technique could be used successfully to determine flavours (diacetyl, pentanedione, acetoin and acetaldehyde) in beer.