THE DETERMINATION OF DIACETYL AND 2,3-PENTANEDIONE IN BEER HEAD SPACE BY GAS CHROMATOGRAPHY

Abstract

A method is described for the direct determination of diacetyl and 2,3-pentanedione in beer head space by gas liquid chromatography using an electron capture detector. The method is sensitive to 0–01 p.p.m. of each diketone. Results are presented showing the analysis of a number of commercially available beers for diacetyl and 2,3-pentanedione by the gas chromatographic method and the corresponding analysis (total vicinal diketones) obtained by an absorptiometric method. The diacetyl and 2,3-pentanedione, as measured by gas chromatography, and the total vicinal diketones, as measured absorptiometrically, are reported for samples drawn throughout a laboratory-scale brewing. Yeast fermentation causes an initial increase in the vicinal diketone content of wort but prolonged fermentation leads to very low levels of both diacetyl and 2,3-pentanedione. It is shown that boiling fermenting wort and beer can cause the release of a considerable amount of both diacetyl and 2,3-pentanedione. This may lead to falsely high results for the vicinal diketones as measured by absorptiometric methods which include a distillation step as part of the procedure.