Role of Elemental Sulfur in Forming Latent Precursors of HS in Wine.

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