Role of Elemental Sulfur in Forming Latent Precursors of H 2 S in Wine

The level of hydrogen sulfide (H 2 S) can increase during abiotic storage of wines, and potential latent sources of H 2 S are still under investigation. We demonstrate that elemental sulfur (S 0 ) residues on grapes not only can produce H 2 S during fermentation but also can form precursors capable of generating additional H 2 S after bottle storage for 3 months. H 2 S could be released from S 0 -derived precursors by addition of a reducing agent (TCEP), but not by addition of strong brine to induce release of H 2 S from metal sulfide complexes. The size of the TCEP-releasable pool varied among yeast strains. Using the TCEP assay, multiple polar S 0 -derived precursors were detected following normal-phase preparative chromatography. Using reversed-phase liquid chromatography and high-resolution mass spectrometry, we detected an increase in the levels of diglutathione trisulfane (GSSSG) and glutathione disulfide (GSSG) in S 0 -fermented red wine and an increase in the levels of glutathione S -sulfonate (GSSO 3 – ) and tetrathionate (S 4 O 6 2– ) in S 0 -fermented white wine as compared to controls. GSSSG, but not S 4 O 6 2–, was shown to evolve H 2 S in the presence of TCEP. Pathways for the formation of GSSSG, GSSG, GSSO 3 –, and S 4 O 6 2– from S 0 are proposed.