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

The level of hydrogen sulfide (H2 S) can increase during abiotic storage of wines, and potential latent sources of H2 S are still under investigation. We demonstrate that elemental sulfur (S0 ) residues on grapes not only can produce H2 S during fermentation but also can form precursors capable of generating additional H2 S after bottle storage for 3 months. H2 S could be released from S0 -derived precursors by addition of a reducing agent (TCEP), but not by addition of strong brine to induce release of H2 S from metal sulfide complexes. The size of the TCEP-releasable pool varied among yeast strains. Using the TCEP assay, multiple polar S0 -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 S0 -fermented red wine and an increase in the levels of glutathione S-sulfonate (GSSO3 - ) and tetrathionate (S4 O6 2- ) in S0 -fermented white wine as compared to controls. GSSSG, but not S4 O6 2- , was shown to evolve H2 S in the presence of TCEP. Pathways for the formation of GSSSG, GSSG, GSSO3 - , and S4 O6 2- from S0 are proposed.