Implementation of headspace solid-phase-microextraction–GC–MS/MS methodology for determination of 3-alkyl-2-methoxypyrazines in wine

Abstract

A solid phase microextraction (HS-SPME)–GC–Tandem MS methodology was established for the analysis of 3-alkyl-2 methoxypyrazines in wine. Due to their low threshold value (2-methoxy-3-isobutylpyrazine, MIBP, 1 ng/l white wine, 10 ng/l red wine) these pyrazines contribute to the typical aroma especially of Sauvignon Blanc and Cabernet Sauvignon wines. The following fibers were tested, varying extraction time (30–80 min), extraction temperature (30–80 °C), ethanol concentration (1.25–6.25% vol) and ionic strength of salt added: carbowax/divinylbenzene (CW/DVB), polydimethylsiloxane/divinylbenzene (PDMS/DVB) and, divinylbenzene/carboxene/polydimethylsiloxane (DVB/CAR/PDMS) and carboxene/polydimethylsiloxane (CAR/PDMS). Best results were obtained with CAR/PDMS. 65 wines (41 Sauvignon Blanc, 24 Cabernet Sauvignon) of worldwide origin were analysed using the established method. The standard wine parameters (density, alcohol, total extract, pH, total acid, reducing sugar) were analysed according to FTIR method (WineScan Foss). MIBP was detectable in 14 Sauvignon Blanc wines, most of them from New Zealand (concentration 10–19 ng/l). In one manipulated Sauvignon Blanc wine from South Africa 173 ng/l MIBP was analysed, more than four to five fold the highest concentration ever found in wine. There is a correlation between the content of MIBP and the aroma profile analysis (descriptive analysis) with best results in a mediate concentration range up to 20 ng/l.