Abstract

Wine yeast expressed proteins are influential during the production of varietal aromatic Sauvignon Blanc wines as they release or mediate aroma compounds and undesirable volatile acidity (VA). As Torulaspora delbrueckii in conjunction with Saccharomyces cerevisiae as well as a S. cerevisiae/T. delbrueckii inter-genus hybrid were previously shown to produce white wine with enhanced aroma and/or lower VA, intra- and novel inter-genus hybrids were trialled for the production of aromatic Sauvignon Blanc with lower VA. The inter-genus hybrid NH 07/1 produced wine with a more positive association with the aroma compound 3-mercaptohexylacetate (3MHA) than two commercial thiol-releasing wine yeast (TRWY) strains, Zymaflore X5 and Zymaflore VL3. The wine also had a negative association with VA, and a positive association with floral and tropical fruit aromas. Three intra-genus hybrids, NH 56, NH 57 and NH 88, produced wines with a negative association with VA, and a positive association with tropical fruit aroma. These wines also had a stronger association with the aroma compound, 3-mercaptohexanol (3MH) than wines produced with all commercial TRWY. The hybrid NH 07/1 and Zymaflore VL3 also over-expressed the lactoylglutathione lyase protein responsible for the release of the volatile thiol, 4-mercapto-4-methyl-pentan-2-one (4MMP) by cleaving its carbon-sulphur bonds. Therefore, lactoylglutathione lyase is a potential biomarker for 3MH-release, as this thiol also contains a carbon-sulphur-bond. Dehydrogenase proteins might also be useful biomarkers for VA formation by fermenting wine yeasts. Three intra- and one inter-genus hybrids with the abiliy to produce aromatic Sauvignon Blanc wines with lower VA compared to commercial TRWY references were identified.

Key words:         Acetic acid, isobaric tags for relative and absolute quantitation (iTRAQ), metabolomic, Orbitrap liquid chromatography tandem mass spectrometry (LC-MS/MS), proteomic, solid phase extraction-gas chromatography coupled to tandem mass spectrometry (SPE GC-MS/MS), volatile thiols.