Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1165482 | Analytica Chimica Acta | 2012 | 9 Pages |
This paper presents methods for the definition of important analytical tools, such as the development of sensitive and rapid methods for analysing reduced and oxidised glutathione (GSH and GSSG), hydroxycinnamic acids (HCA), bound thiols (GSH-3MH and Cys-3MH) and free thiols (3MH and 3MHA), and their first application to evaluate the effect of reductive winemaking on the composition of Lugana juices and wines.Lugana is a traditional white wine from the Lake Garda region (Italy), produced using a local grape variety, Trebbiano di Lugana. An innovative winemaking procedure based on preliminary cooling of grape berries followed by crushing in an inert environment was implemented and explored on a winery scale.The effects of these procedures on hydroxycinnamic acids, GSH, GSSG, free and bound thiols and flavanols content were investigated. The juices and wines produced using different protocols were examined. Moreover, wines aged in tanks for 1, 2 and 3 months were analysed.The high level of GSH found in Lugana grapes, which can act as a natural antioxidant and be preserved in must and young wines, thus reducing the need of exogenous antioxidants, was particularly interesting. Moreover, it was clear that polyphenol concentrations (hydroxycinnamic acids and catechins) were strongly influenced by winemaking and pressing conditions, which required fine tuning of pressing.Above-threshold levels of 3-mercaptohexan-1-ol (3MH) and 3-mercaptohexyl acetate (3MHA) were found in the wines and changed according to the winemaking procedure applied. Interestingly, the evolution during the first three months also varied depending on the procedure adopted. Organic synthesis of cysteine and glutathione conjugates was carried out and juices and wines were subjected to LC–MS/MS analysis. These two molecules appeared to be strongly affected by the winemaking procedure, but did not show any significant change during the first 3 months of post-bottling ageing. This supports the theory, already proposed in the literature, that there are other synthetic pathways for free thiol formation.
Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► New LC–MS method for the analysis of reduced and oxidised glutathione and methionine. ► Improved quantification of free varietal thiols by means of GC–MS/MS. ► Improved quantification of bound varietal thiols by means of UPLC–MS/MS. ► Free and bound varietal thiols identified for the first time in Lugana wines. ► Developed methods effective in evaluating the process of winemaking of Lugana wine.