International audienc

This study investigated the increase of beta-damascenone content during aging in a variety of commercial Belgian beers. Quantities detected in fresh beers were generally low (from 6 ng/g to 25 ng/g). After 5 days at 40 degrees C, the level increased (to as much as 210 ng/g) in most of the beers studied, according to the type of beer. Further experiments showed that wort initially contains large quantities of beta-damascenone (450 ng/g), but that degradation of the compound during fermentation accounts for the low concentrations observed in fresh beers. Production during beer aging can be partially explained by acid hydrolysis of glycosides.

Combinatorial chemistry was used to extend the knowledge of beer thiols by synthesizing 13 mercapto primary alcohols and 6 other compounds (mercapto ketones and corresponding alcohols). Their respective mass spectra, retention indices on two columns, odor descriptors, and best estimated-gas chromatography-lowest amounts detected sniffing (BE-GC-LoADS) are reported. The descriptor "cheese", commonly associated with mercapto aldehydes and thioesters, was rarely used for mercapto alcohols or mercapto ketones. Polyfunctional thiols containing at least six carbon atoms usually gave a delicate odor of rhubarb/carrot, whereas most of the mercapto primary alcohols of intermediate size were described as onion-like, plastic-like, or pungent. Sensorial analysis of beers spiked with copper(II) ions allowed confirmation of the participation of thiols in the overall odor of fresh beer. The finding of 4-mercapto-4-methyl-2-pentanone and 3-mercaptohexanol in an XAD-2 Amberlite resin beer extract indicates a requirement for a more efficient thiol extraction procedure allowing identification of relevant polyfunctional thiols for brewing scientists.

No abstract

No abstract