title: New precursor of 3-mercaptohexan-1-ol in grape juice: thiol-forming potential and kinetics during early stages of must fermentation.
abstract: Two volatile thiols, 3-mercaptohexan-1-ol (3MH) and 3-mercaptohexyl acetate (3MHA), are key aroma impact compounds in many young white wines, especially of the variety Sauvignon blanc (SB). Although great effort has been invested to identify their precursors in recent years, the origin of the majority of 3MH and 3MHA generated during wine fermentation still cannot be explained. Here we demonstrate that supplying an external source of hydrogen sulfide to grape juice hugely increases its thiol-forming potential. We further describe the discovery of (E)-2-hexen-1-ol as an additional new thiol precursor and demonstrate that it possesses, together with (E)-2-hexenal, an immense thiol-forming potential during fermentation. Both C6-compounds are extremely rapidly metabolized by yeast during the first hours after inoculation, even under commercial conditions, and can be interconverted during this phase depending on their initial concentration in the grape juice. Spiking grape juice with additional acetaldehyde greatly enhanced the (E)-2-hexen-1-ol to (E)-2-hexenal conversion rate. Delaying the metabolization of the two unsaturated C6-thiol precursors by yeast, at the same time as increasing hydrogen sulfide production early in fermentation, opens up a great opportunity to tap into this enormous potential 3MH and 3MHA source in grape juice and extends the possibility of thiol production to other non-grape-based alcoholic beverages as well.
authors.affiliation: Pernod Ricard New Zealand, Riverlands, Blenheim 7274, New Zealand. mihar@gmx.de.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Harsch
authors.forename: Frank
authors.initials: F
authors.lastname: Benkwitz
authors.forename: Andy
authors.initials: A
authors.lastname: Frost
authors.forename: Benoît
authors.initials: B
authors.lastname: Colonna-Ceccaldi
authors.forename: Richard C
authors.initials: RC
authors.lastname: Gardner
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Salmon
mesh_terms: D000085:Acetates / Q000032:analysis* / Q000378:metabolism; D000447:Aldehydes / Q000032:analysis* / Q000378:metabolism; D001628:Beverages / Q000032:analysis*; D005285:Fermentation; D005638:Fruit / Q000737:chemistry*; D000441:Hexanols / Q000032:analysis* / Q000378:metabolism; D007700:Kinetics; D009812:Odorants; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000032:analysis* / Q000378:metabolism; D013649:Taste; D027843:Vitis / Q000737:chemistry*; D014920:Wine / Q000032:analysis
chemical_list: C443379:3-mercaptohexan-1-ol; D000085:Acetates; D000447:Aldehydes; D000441:Hexanols; D013438:Sulfhydryl Compounds; C051750:2-hexenal; C513640:3-mercaptohexyl acetate