Primary odorants of pale lager beer - Differences to other beers and changes during storage

Application of an aroma extract dilution analysis to the flavour concentrate of a pale lager beer revealed 33 primary odorants (FD factors ranging over 16 to 1024) among which 3-methylbutanol, 2-phenylethanol, 4-vinyl-2-methoxyphenol, 3- and 2-methylbutanoic acid, 2,5-dimethyl-4-hydroxy-3(2 H)-furanone (furaneol) and butanoic acid showed the highest FD factors. With a somewhat lower FD factor ethyl butanoate, 4,5-dimethyl-3-hydroxy-2(5 H)-furanone (sotolone), ethyl hexanoate, hexanoic acid and (E)-β-damascenone contributed to the overall flavour. Compared to the pale lager beer, the odour activity value (OAV; ratio of concentration to odour threshold) of furaneol in a dark lager beer and of 4-vinyl-2-methoxyphenol in a wheat beer, was significantly higher. Sensory experiments corroborated that these odorants were important contributors to the overall flavour of the dark lager and the wheat beer, respectively. In two alcohol-free beers the OAVs of eight of the most important odorants were markedly lower. After storage of a pale lager beer (14 d; 40° C), which had been spiked with oxygen, the FD factors of most of the primary odorants of the fresh beer remained unchanged. On the other hand, phenylacetaldehyde, 3-methyl-3-mercaptobutylformate (catty, Ribes odour) and an unknown compound with a sweet, aniseed-like note appeared as additional important odorants in the stored sample.