Fractionated stir bar sorptive extraction using conventional and solvent-assisted approaches for enhanced identification capabilities of aroma compounds in beverages.

For successful profiling of aroma carriers in food samples, a highly efficient extraction method is mandatory. A two-step stir bar sorptive extraction (SBSE) approach, namely fractionated SBSE (Fr-SBSE), was developed to improve both the organoleptic and the chemical identification of aroma compounds in beverages. Fr-SBSE consists of two multi-SBSE procedures (SBSE) performed sequentially on the same sample. The first extraction consists of a conventional SBSE using three polydimethylsiloxane (PDMS) stir bars (1SBSE). This is followed by a solvent-assisted SBSE performed on the same sample using three solvent-swollen PDMS stir bars (2 SA-SBSE). The 1SBSE mainly extracts apolar/medium polar solutes with log K values >2, while the 2 SA-SBSE mainly extracts polar solutes with log K values <2. After this two-step fractionation procedure, either thermal desorption (TD) or liquid desorption - large volume injection (LD-LVI), followed by GC-MS is performed on each set of three stir bars. A real-life sample of roasted green tea was used for method development. The performance of the Fr-SBSE method is further illustrated with sensory evaluations and GC-MS analysis for a stout beer sample. Compared to an extraction procedure with SA-SBSE only, Fr-SBSE including a 1SBSE and a 2 SA-SBSE reduced co-elution of aroma compounds in the chromatograms and was capable of providing improved mass spectral quality for identification of 17 additional compounds in roasted green tea, and 12 additional compounds in stout beer, respectively. Moreover, odor description and characterization were clearly improved.