Emerging Analytical Techniques for the Assessment of Aroma Relevant Sulfur Compounds in Coffee

Aroma extraction by solid phase micro extraction (SPME) was combined with comprehensive two-dimensional gas chromatography (2D-GC) using two column configurations and detection by time-of-flight mass spectrometry (TOF-MS) for the quantitative assessment of trace sulfur compounds in coffee. Based on the optimization of 2D separation and TOF-MS detection parameters, quantification assays were established for 3-methyl-2-butene-1-thiol (MBT) and 3-(methylthio)propionaldehyde (methional). The quantification of these compounds in roast and ground (R&G) coffee as well as in filter coffee brew resulted in satisfactory detection limits and repeatability of the method. Furthermore, quantitative results highlighted the importance of MBT in the aroma above a freshly ground coffee. Data indicated that it is almost quantitatively lost during preparation of filter coffee beverage due to evaporation and degradation. In contrast, methional was found quite abundant in R&G coffee and is highly recovered in the final beverage. In addition, identification was compared to standard methods comprising aroma isolation by high vacuum transfer and solvent aroma extraction. The evaluation of the solvent extract by 2D-GC-TOFMS as well as GC-olfactometry resulted in fewer sulfur compounds identified, thus indicating high degradation rates of reactive sulfur compounds during