Volatile constituents of beer

The principal higher alcohols found in beer are 3-methylbutanol (isoamyl alcohol), 2-methylbutanol aciive-eonyl alcohol), 2-methylpropanol (isobutyl alcohol), propanol, and phenethyl alcohol (Table 22.9). It is noteworthy that the levels of higher alcohols in home-brewed beer and wines is at least 10 times higher than those in the commercial products [61]. The major volatile constituents of beer are most conveniently examined by gas chromatography either of the beer directly or of the gas in the head space above the beer in bottle. The ASBC recommend direct injection on to a 20% Carbowax 20M column at 80°C. In order to identify and estimate the minor volatile constituents it is usually necessary to prepare a solvent extract of the beer or a distillate. It may be desirable to fractionate the solvent extract by adsorption chromatography before examination by capillary gas chromatography-mass spectrometry [43, 59]. 

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