Flavor chemistry of beer: part ii: flavour and threshold of 239 aroma volatiles.

Meilgaard, M.C.

Abstract
The flavour thresholds of the 239 compounds examined varied widely and it is therefore not surprising that on occasion, compounds of high chemical purity (99%+) were organoleptically impure or even mis flavoured. Proof of organoleptic purity requires repeated purification until a constant flavour and a constant threshold are obtained. In each homologous series, the compounds containing 5 to 10, and usually 7 to 10 carbon atoms show the strongest flavour. The purified fusel alcohols were found to have pleasant aromatic flavours. Some sulphur compounds show threshold values which are several orders of magnitude below our present limits of detection by analysis. The flavour and threshold of a given compound can often be predicted quite reliably from the data presented. The significant flavour constituents of fresh beer are, in the approximate order of their importance, ethanol, the hop bitter substances, carbon dioxide, the banana esters, the apple esters, and the fusel alcohols. In beers which are off-flavoured (sulphury, diacetyl-like, or stale) the corresponding flavour compounds dimethyl sulphide, hydrogen sulphide, diacetyl, and 2-trans-nonenal can play a much greater role than any of the normal flavour constituents.
Keywords: alcohol aroma beer ester fatty acid flavour organic acid sulphur compound taste test volatile compound