The level of hydrogen sulfide (H2S) can increase during abiotic storage of wines, and potential latent sources of H2S are still under investigation. We demonstrate that elemental sulfur (S0) residues on grapes not only can produce H2S during fermentation but also can form precursors capable of generating additional H2S after bottle storage for 3 months. H2S 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 H2S 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 (S4O62-) in S0-fermented white wine as compared to controls. GSSSG, but not S4O62-, was shown to evolve H2S in the presence of TCEP. Pathways for the formation of GSSSG, GSSG, GSSO3-, and S4O62- from S0 are proposed.
Keywords: flavor precursor; pesticide degradation; sulfur-like off aroma; wine fault; wine reduction.