Optimisation of HS-SPME conditions with a response surface methodology and development of a fast GC/MS method to quantify ethyl acetate in sweet wines

Noble-rot sweet white wines generally present an intense, complex aromatic profile characterised by fruity (citrus, dried apricot, candied orange), spicy and floral notes. However, during barrel or bottle ageing, some of them develop an unpleasant solvent or nail polish remover odour characteristic of a high concentration of ethyl acetate. This study proposes a rapid solvent-free SPME-GC/MS method to quantify ethyl acetate that is sufficiently fast, sensitive, accurate and reliable to study its evolution over time. A central composite design and the response surface methodology were used to determine the optimal extraction conditions (ionic strength, temperature, equilibration, and extraction time). Compared to the official OIV method based on distillation followed by GC/FID analysis, the method appeared to be more repeatable (RSD < 2.9%), reproducible (RSD < 4.8%), accurate and sensitive (LOQ < 0.16 mg/L). The method was used to assay ethyl acetate in noble-rot and air-dried sweet wines from different vintages and origins. Preliminary results indicate (1) that the concentration of ethyl acetate appeared to be higher in older wines, and (2) that origin or production process did not seem to be the main factors influencing the ethyl acetate concentration.