title: Quantification of several 4-alkyl substituted gamma-lactones in Australian wines.
abstract: Stable isotope dilution assays have been developed for gamma-octalactone (1), gamma-nonalactone (2), gamma-decalactone (3) and gamma-dodecalactone (4) in both white and red wines for the first time. (2)H(7)-analogues of each lactone were prepared for use as internal standards via a strategy employing ring-opening, esterification and oxidation of the respective starting lactones. The methods were shown to be highly accurate and reproducible (R(2) > or = 0.999; SD < or = 1%). A large selection of Australian wines (n = 178) were analyzed for the presence of lactones 1-4. Fifty-eight white wines covering the varieties Chardonnay, Riesling, Sauvignon Blanc, Semillon and Viognier, as well as Botrytis style wines, were analyzed and showed broadly that gamma-octalactone (1) was the most common lactone, being observed above its limit of detection in 28 of the wines, followed by gamma-nonalactone (2) in 23 wines. The Botrytis style white wines had the highest concentrations of 1 and 2 (maximum concentrations 8.5 and 59 microg/L respectively). A total of 120 red wines covering the varieties Cabernet Sauvignon, Durif, Merlot, Pinot Noir and Shiraz were also studied and showed gamma-octalactone (1) and gamma-nonalactone (2) to be the most common lactones present, in 56 and 57 of the wines, respectively. gamma-Decalactone (3) was observed in only a small number (13) of red wine samples and not at all in the white varieties. gamma-Dodecalactone (4) was absent from all 178 samples studied. The highest concentrations of lactones 1, 2 and 3 in the red wines were 4.2, 39.7 and 4.0 microg/L respectively.
authors.affiliation: School of Chemistry, Physics and Earth Sciences, Flinders University, Adelaide, Australia.
authors.forename: Rachel C
authors.initials: RC
authors.lastname: Cooke
authors.forename: Dimitra L
authors.initials: DL
authors.lastname: Capone
authors.forename: Katryna A
authors.initials: KA
authors.lastname: van Leeuwen
authors.forename: Gordon M
authors.initials: GM
authors.lastname: Elsey
authors.forename: Mark A
authors.initials: MA
authors.lastname: Sefton
mesh_terms: D001315:Australia; D007783:Lactones / Q000737:chemistry*; D014920:Wine / Q000032:analysis*
chemical_list: D007783:Lactones