New Zealand wine exports exceeded $1b in 2009, with Sauvignon Blanc being more than 75% of that total. New Zealand SB is famous for its distinctive aroma which is driven by a key group of compounds called volatile thiols. 3-mercaptohexyl acetate (3MHA), 3-mercaptohexan- 1-ol (3MH) and 4- 4-mercapto-4-methylpentan-2-one (4MMP) are responsible for the passionfruit, grapefruit and box tree (cats pee) aromas in the wine respectively. These compounds are absent in grape juice, but the yeasts convert odourless precursors of grape juice to volatile thiols. Thiol concentrations in wine can vary up to 20-fold, depending on season, vineyard and region. Detailed chemical analysis of grape juices could become an important tool for winemakers to decide which juices should be used for making premium wines before starting fermentations in the winery. Main objectives of this project are:
- to establish rapid methods to assay as many metabolites in grape juice as possible, which will allow us to predict the final wine quality at the time of entry to the winery;
- to provide a biochemical basis for improved selection of juices for different styles and batches of wine.
We are using different analytical tools, such as, gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), Fourier Transform Infrared Spectroscopy (FTIR-WineScan) and Nuclear Magnetic Resonance (NMR) to analyze grape juices, identify and quantify metabolites in the juices, and correlate metabolite levels with levels of volatile thiols in the fermented wines.
Pinu, F.R., Edwards, P.J. B. S., Jouanneau, Kilmartin, P.A., Gardner, R.C. and Villas-Boas, S. G. Sauvignon blanc metabolomics: grape juice metabolites affecting the development of varietal thiols and other aroma compounds in wines. 2013. Metabolomics. Vol.9. Issue 6. doi:10.1007/s11306-013-0615-9 >>>
Pinu, F.R.; Jouanneau, S.; Nicolau, L.; Gardner, R.C.; Villas-Boas, S.G. 2012. Concentrations of the volatile thiol 3-mercaptohexanol in Sauvignon Blanc wines: No correlation with juice precursors. American Journal of Enology and Viticulture 63: 407 – 413. doi:10.5344/ajev.2012.11126 >>>