TuP-07
DEVELOPMENT OF A SIMPLE AND ACCURATE ANALYTICAL METHOD FOR DIACETYL IN WINE USING SPME AND GC-MS
Yoji Hayasaka, Tim Burvill and Eveline Bartowsky
The Australian Wine Research Institute, Waite Road, Urrbrae, SA, Australia
Correspondence to PO Box 197, Glen Osmond, SA 5064
Diacetyl (2,3-butanedione) is an important flavour compound in wine, having a nutty or buttery character and is formed during alcoholic and malolactic fermentations. Aroma sensory thresholds for diacetyl in wine are 0.2 mg/l in Chardonnay, 0.9 mg/l in Pinot noir and 2.8 mg/l in Cabernet Sauvignon [1]. Diacetyl contributes to the favourable complexity in wine but levels above 5-7 mg/l may be undesirable [2].
Various methods for the quantification of diacetyl in beverages have been developed and most of the methods involve distillation, concentration and/or extraction prior to instrumental analysis. The aim was to develop a new analytical method for diacetyl in wine that was rapid, easy, sensitive and accurate.
Solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) techniques were applied and a deuterated analogue of diacetyl, d6-diacetyl, as internal standard was used for determination of diacetyl concentration in wine. Advantages of the method are thought to be as follows:
- Distillation, solvent extraction or derivatisation of diacetyl prior to instrumental analysis was not required.
- Sample preparation by SPME was a very simple and less time-consuming step.
- GC-MS offered a very sensitive and selective method for the detection of diacetyl.
- The deuterated internal standard ensured reproducibilty and accuracy of the method.
Control experiments confirmed the stability of the d6-diacetyl internal standard under analysis conditions. The detection limit was less than 0.01 mg/l in the synthetic wine and the quantification curve showed excellent linearity throughout a range of 0.1 to 10 mg/l. The analysis was carried out on synthetic, red and white wine to investigate the influences of different strains of the malolactic bacterium, Oenococcus oeni, on the production of diacetyl during wine making.
1. Martineau B., Acree T.E. & Henick-Kling T., Food Research International, 1995, 28, (2),139-143.
2. Rankine B.C., Fornachon J.C.M. & Bridson A., 1969, Vitis, 8, 129-134.