Application of GC/MS method using SPE columns for quantitative determination of diacetyl and 2,3-pentanedione during beer fermentation

Abstract

A new gas chromatography/mass selective detector method for determination of diacetyl and 2,3-pentanedione was developed. Diacetyl and 2,3-pentanedione were derivatized with 1,2-diaminobenzene to form 2,3-dimethylquinoxaline and 2-ethyl-3-methylquinoxaline, respectively. The amounts of formed 2,3-dimethylquinoxaline and 2-ethyl-3-methylquinoxaline were proportional to the diacetyl and 2,3-pentanedione concentrations present in the sample. 2,3-Dimethylquinoxaline and 2-ethyl-3-methylquinoxaline were extracted using solid-phase extraction (SPE) columns and determined by gas chromatography using a mass selective detector. Extraction by SPE columns proved to be very rapid, simple, and precise. This method was applied for the determination of diacetyl and 2,3-pentanedione concentrations during beer fermentation (primary fermentation and maturation). During fermentation, diacetyl and 2,3-pentanedione were quantified to demonstrate the suitability of the method. Primary fermentations were carried out at different temperatures (8 and 14°C) and an industrial bottom-fermented yeast strain was used. Corn grits, beside malt, were used for wort production. The level of corn grits varied from 10-40%. Diacetyl and 2,3-pentanedione formation and reduction were strongly influenced by temperature and the rates for both increased with an increase in primary fermentation temperature. The highest diacetyl and 2,3-pentanedione concentrations (0.6365 mg/L and 0.8192 mg/L, respectively) were obtained during fermentation with 40% corn grits at 14°C. © 2006 American Society of Brewing Chemists, Inc.