A novel mass spectrometry method was developed for the rapid quantification of odor-active volatiles in food matrices. Quantitative analyses of trace-level volatile compounds are routinely performed as an objective measure of flavor in foodstuffs and raw materials. Standard analytical methods based on gas chromatography-mass spectrometry (GC-MS) usually require 30-60 minutes/sample. This low throughput is poorly suited for several emerging directions in flavor research or process control which can potentially create thousands of samples, e.g. characterization of breeding populations, as well as characterization of raw materials. Ambient ionization (AI) techniques like DART-MS are much faster, but with the drawback of lower sensitivity/ selectivity. A sorbent-coated mesh was developed for the extraction and pre-concentration of volatiles (Solid Phase Mesh Enhanced Sorption from Headspace, SPMESH), which could then be analyzed by Direct Analysis in Real Time (DART)-MS. The SPMESH coating material was optimized for the extraction of odor-active volatiles in complex food matrices. In combination with high resolution mass spectrometry (HRMS), SPMESH-DART could obtain detection limits below sensory thresholds for a variety of compounds with olfactory relevance in food matrices. The new method was validated in grape macerates, exhibiting excellent agreement with established GC-MS methodology (r2≥0.90).
In a separate study, the mechanism for evolution of hydrogen sulfide during storage of wines fermented on elemental sulfur was investigated. Hydrogen sulfide (H2S) is frequently found in faulted wines with sulfurous off-aromas. H2S is reported to increase during bottle storage of some wines, and the identity of all potential precursors responsible for this latent H2S is still not resolved. We have shown that elemental sulfur residues (S0) on grapes can not only produce H2S during fermentation, but also yield wine-soluble intermediates capable of generating more H2S during storage. Through HPLC – high resolution mass spectrometry, we identified H2S-releasing polythionates in the S0 fermented wine sample that are absent in the control, and propose a mechanism for the formation of a supplementary S0-derived source.