Passion fruit, grapefruit, boxwood: Müller Thurgau has these characteristic aromas that are determined by 'varietal thiols', volatile sulphur compounds that are responsible for the aromatic profile and that in this wine are at concentrations that are far above the sensory thresholds.
This has been discovered by a research conducted by the Edmund Mach Foundation in collaboration with six universities (Bologna, Naples, Padua, Turin, Trento and Verona) on the study of varietal sulphur compounds and their role in contributing to the aroma of Italian white wines, which was presented on Thursday 30 June at the opening of the "35th International Müller Thurgau Review: Mountain Wine" in Cembra.
Importance of the research
The work, published these days in the journal Food Research International, defines in detail the aromatic characteristics of certain varieties, among which the case of Müller Thurgau stands out. The thiol character is well present in the grapes of this variety as well as in the wines, thanks to precision vinification. This evidence confirms how winemakers have been able to exploit the characteristics of the grape variety in the vinification process, bringing these 'identity' sensory notes into the bottle, which are particularly appreciated by consumers.
The 'D-Wines' project: 246 wines from 18 different Italian monovarietal wines analysed
The 'D-Wines' project involved the analysis and tasting of 246 wine samples belonging to 18 different Italian monovarietal wines representative of Italian regions and selected in conjunction with the producer associations.
Varietal thiols, decisive compounds in defining the aromatic characteristics of wines
Varietal thiols are part of the volatile compounds responsible for the aromatic profile of wine and are characterised by being easily recognisable and having a high sensory impact even at low concentrations. They are part of those classes of "identity" volatile compounds, present in lower quantities than fermentation aromas, but decisive in defining the aromatic characteristics of wines and their specificity and sensory recognisability. They constitute the aromatic component of wine that is most directly influenced by the grape variety used for vinification; for this reason they are defined as 'varietal'. They include terpenes, norisoprenoids, pyrazines and certain sulphur compounds, such as varietal thiols.
These compounds are present in the form of non-odorous precursors in the grapes and are released during vinification, when the fermentation conditions set by the winemaker permit, and contribute to the wine's aromatic intensity and complexity.
Usefulness of the research: new method for analysing thiols developed
Despite their predominant role in defining wine aroma, the quantification of varietal thiols is a complex operation, being influenced by countless factors attributable to the nature of the wine and the thiols themselves. The research carried out by the D-Wines consortium, which at the FEM has counted on the highly qualified skills and instruments of the Metabolomics Unit, has enabled three objectives to be achieved:
The development of a highly sensitive method used for the analysis of varietal thiols by FEM and UniTN researchers in around 300 wines. This included 246 white wines (including 13 Müller Thurgau from Trentino) from 2019 and a further 50 Müller Thurgau from 2019 and 2020. It found that in the vast majority of the Müller Thurgau wines, all the varietal thiols analysed are at concentrations exceeding, even by far, the sensory thresholds. These are exceeded up to 12 times for 4-methyl-4-sulfanil-pentanone (4-MSP) and up to 66 times for 3-sulfanil-hexanol (3-SH).
The sensory descriptive analysis of 249 samples of 18 varieties by a panel of oenologists at the University of Naples found that the particular olfactory notes of Müller Thurgau with a characteristic 'thiol character', with hints of passion fruit, boxwood/cat's pee and grapefruit, could be sensitively highlighted.
Sensory classification analysis, by a second panel of oenologists at the University of Bologna, again showed that these 'thiolic' descriptors were well represented in all the Müller Thurgau wines analysed.
Link to the full text of the research
https://www.sciencedirect.com/science/article/pii/S0963996922004616
Source: FEM
