QUANTITATIVE ANALYSIS OF DIACETYL, PENTANEDIONE AND THEIR PRECURSORS DURING BEER FERMENTATION BY AN ACCURATE GC/MS METHOD

Authors:
  • SLSophie Landaud
    Sophie Landaud
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Abstract
A GC/MS method previously described for diacetyl was developed for the quantification of 2,3-pentanedione, and the derivatization procedure was modified for the determination of α-acetohydroxy acid. The reaction of 2,3-pentanedione with 4,5-dichloro-1,2-diaminobenzene produced 6,7-dichloro-2-methyl-3-ethylquinoxaline (DCMEQ), which was extracted with toluene and determined by gas chromatography using a mass selective detector. The formation of DCMEQ was linearly correlated with the 2,3-pentanedione concentration. The method was very simple and sensitive. The detection limit of the 2,3-pentanedione derivative and diacetyl derivative was 0.0007 mg/litre and 0.0002 mg/litre of the toluene extract respectively, and the determination limit was 0.001 mg/litre and 0.0007 mg/litre, respectively. Cautious sample treatment led to a low (10%) and controlled conversion of α-acetohydroxy acids to vicinal diketones. This reproducible percentage of conversion made it possible to determine precisely free vicinal diketones and α-acetohydroxy acids. The method was applied to the determination of precursors and vicinal diketones concentrations during beer fermentation.

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