title: Quantification of Polyfunctional Thiols in Wine by HS-SPME-GC-MS Following Extractive Alkylation.
abstract: Analyses of key odorous polyfunctional volatile thiols in wines (3-mercaptohexanol (3-MH), 3-mercaptohexylacetate (3-MHA), and 4-mercapto-4-methyl-2-pentanone (4-MMP)) are challenging due to their high reactivity and ultra-trace concentrations, especially when using conventional gas-chromatography electron impact mass spectrometry (GC-EI-MS). We describe a method in which thiols are converted to pentafluorobenzyl (PFB) derivatives by extractive alkylation and the organic layer is evaporated prior to headspace solid phase microextraction (HS-SPME) and GC-EI-MS analysis. Optimal parameters were determined by response surface area modeling. The addition of NaCl solution to the dried SPME vials prior to extraction resulted in up to less than fivefold improvement in detection limits. Using 40 mL wine samples, limits of detection for 4-MMP, 3-MH, and 3-MHA were 0.9 ng/L, 1 ng/L, and 17 ng/L, respectively. Good recovery (90%-109%) and precision (5%-11% RSD) were achieved in wine matrices. The new method was used to survey polyfunctional thiol concentrations in 61 commercial California and New York State wines produced from V. vinifera (Riesling, Gewürztraminer, Cabernet Sauvignon, Sauvignon blanc and non-varietal rosé wines), V. labruscana (Niagara), and Vitis spp. (Cayuga White). Mean 4-MMP concentrations in New York Niagara (17 ng/L) were not significantly different from concentrations in Sauvignon blanc, but were significantly higher than 4-MMP in other varietal wines.
authors.affiliation: Department of Food Science, Cornell University, Stocking Hall, 411 Tower Road, Ithaca, NY 14853, USA. lem248@cornell.edu.
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Musumeci
authors.affiliation: Department of Food Science, Cornell University, Stocking Hall, 411 Tower Road, Ithaca, NY 14853, USA. ir45@cornell.edu.
authors.forename: Imelda
authors.initials: I
authors.lastname: Ryona
authors.affiliation: Gallo Winery, 600 Yosemite Boulevard, Modesto, CA 95354, USA. Bruce.Pan@ejgallo.com.
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Pan
authors.affiliation: Gallo Winery, 600 Yosemite Boulevard, Modesto, CA 95354, USA. Natalia.Loscos@ejgallo.com.
authors.forename: Natalia
authors.initials: N
authors.lastname: Loscos
authors.affiliation: Gallo Winery, 600 Yosemite Boulevard, Modesto, CA 95354, USA. Hui.Feng@ejgallo.com.
authors.forename: Hui
authors.initials: H
authors.lastname: Feng
authors.affiliation: Gallo Winery, 600 Yosemite Boulevard, Modesto, CA 95354, USA. Mike.Cleary@ejgallo.com.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Cleary
authors.affiliation: Department of Food Science, Cornell University, Stocking Hall, 411 Tower Road, Ithaca, NY 14853, USA. gls9@cornell.edu.
authors.forename: Gavin L
authors.initials: GL
authors.lastname: Sacks
mesh_terms: D000478:Alkylation; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D057230:Limit of Detection; D015203:Reproducibility of Results; D052617:Solid Phase Microextraction / Q000379:methods*; D013438:Sulfhydryl Compounds / Q000032:analysis*; D014920:Wine / Q000032:analysis*
chemical_list: D013438:Sulfhydryl Compounds
keywords: Vitis labruscana; extractive alkylation; polyfunctional thiols; wine