Mountain bubbles with identity card

Apertura_portaleA research work which was recently carried out revealed the aromatic identity card of Trentodoc, identified new markers of aging for sparkling wines and allowed to re-evaluate the methods of zonation in a modern way.
This research was coordinated by Andrea Marchetti, University of Modena and Reggio Emilia, and Fulvio Mattivi, alongside with the researchers who work at metabolomics and isotope traceability platforms of Edmund Mach Foundation at San Michele all’Adige (Trentino, Italy). The aim consisted in identifying new methods and technological platforms suitable for research and monitoring concerning traceability of Italian wines. The researchers from Emilia, alongside with the ones from Trentino, took as a case study the traceability of Lambrusco wines from Modena and Trentodoc. They analyzed not only aromatic compounds with untarget approach, but also genetic profiles as well as isotope ratios and their traceability, from the ground to the different organs of the plant, up to must and wines.
The results, which allowed for the first time to characterize the complexity of flavour profile for Trentodoc, analyzed by means of the methods of metabolomics, were presented by Fulvio Mattivi during the recent international IVAS2015 (In Vino Analytica Scientia) meeting , which took place at Mezzocorona (TN) in July 2015. These results will be published in full within the end of this year in a scientific magazine.

The applied method

The analytical technique that was used consists in two-dimensional gas chromatography with time of flight mass detector (ToF GCxGC MS) and allowed to analyze in a relatively short time, and with a simplified sample preparation, samples of sparkling wine produced with metodo classico. The samples were chosen from the ones produced by thirty-seven member companies registered to the register of Trento Doc (controlled designation of origin) and commercially available in January 2013, in addition to reference samples, for a total of about 70 wines.
The choice of using commercial wines, with all their variability inherent their production year (among the analyzed ones, wines from six different vintages were present), their variety composition and all technological steps (the ones related to fermentation, use of wood, or choice of liqueur d’expedition), was dictated by a specific philosophy in the approach to the problem. It required expanding as much as possible the research field. Fulvio Mattivi explains: “We researchers tend to be, as it were, “reductionists”, and generally proceed inductively, circumscribing our experiments to a controlled, and therefore often very limited, case history, and then try to generalize our results. In this case, and in general in the majority of the most complex experiments that we are facing, we chose to work in deductive way, by inserting in the experiment as much complexity was present in the reality of the product we were going to investigate, to identify experimentally which rules could be applicable to our samples, which had an excellent chance to be valid for any other wine of the same population“.
This kind of approach and analysis tried to analyze whether it was still possible, even for a sparkling wine – considered a very technological product – after all the steps related to its production, to identify the imprint given by a specific territory and therefore trace their origin.
In order to assess the ability to detect the differences between the sparkling wines of Trentino and those produced in other regions, at this point it was necessary to find a reference that was as close as possible. A choice for Franciacorta was made: this wine is characterized by the same high quality level, same latitude and varietal composition as Chardonnay and Pinot Noir.

A complexity that has still to be explored

The first result was the confirmation of the enormous complexity – mostly still unexplored – concerning sparkling wines, in which 1,695 volatile compounds in total were observed. Out of these, 969 represent the common matrix and are present in more than two-thirds of the analyzed samples. The other 725 compounds are present only in some of them and they are the ones that contain information related to corporate identity, with the choices concerning varietal composition, use of wood, oenologist’s choice, etc.
The territorial answer, the one that distinguishes Trentodoc from the other sparkling wines produced with metodo classico (represented by Franciacorta ones in the dataset of this study) is found in the remaining 969 compounds, which generated a pool of more than 196 statistically significant variables. These ones, in a multivariate space, place all Trentodoc wines in a distinct position.
Mattivi explains: “From the deepening of the chemical classes of the identified compounds, three evidences emerge. The first one is related to the higher presence in Trentodoc wines, in both qualitative and quantitative terms, of aromatic varietal compounds, in particular the ones belonging to the class of terpenes. The second evidence is that, on the contrary, the compounds of the aromatic spectrum related to the management of the two fermentations, autolysis, and stand on the yeast are mainly present in Franciacorta wines. The last point is that C6 compounds (not all important at the sensorial level), mostly related to the conditions of crushing and pressing, are on average more present in the wines of Trentino”.

What explains the identified differences?

Mattivi continues: “These results seemed to us altogether explicable in terms of identity, because it is widely and generally accepted that the flavour profile of Trentodoc, due to the influence of the microclimate of mountain environment, reflects more faithfully the characteristics in terms of aroma of both grapes and wine with which the production begins. On the other hand, as for such other products as Champagne or Franciacorta, it seems that the flavour profile is less affected by the so-called technological factors. The increased presence of compounds extracted in the processing stages of the grapes, such as C6, can be explained in terms of technology, because while in Franciacorta pressing whole grapes is compulsory, the grapes used for base wine in Trentino are mostly destalked and crushed before pressing. Therefore, this operation takes place under different conditions”.

New ageing markers

The second question the researchers from Trentino asked themselves and about which they questioned the data set obtained from the analysis of the samples was if in the group of Trentodoc wines there were differences related to ageing.
Mattivi explains: “In this case, too, the differences allow distinguishing almost one hundred marker compounds of ageing, able to differentiate significantly young wines, with less than two years on dregs, with more or less aged reserves. This result is in line with the organoleptic evolution of wines which, having a large reserve of bound aromas and precursors, acquire over time more and more complexity”. This also underlines how at the application level this result makes it possible, with the same analysis, to verify whether a bottle has undergone the ageing declared on its label.
The compounds that change more during ageing belong to the group of norisoprenoids, sulphur compounds and their esters and acetals. Many of them are still unknown and some scientists began to identify and quantify them in order to define their influence on the sensory profile of wines.

Traceability, but also zonation

A so complex and demanding study from the economic point of view, too – for the use of very sophisticated equipment – as the one realized at San Michele, produces an amount of processable results, containing information that in most cases do not end in giving an answer to the questions asked by the starting project.
Mattivi comments: “In our work we started with a goal of traceability and we actually succeeded in tracking differences that later sent us back to the grape quality and extracting conditions. However, the compounds we found also give us information on the environment, as it is known how terpenes and norisoprenoids change in function of both thermal regime and environmental conditions in which the vine is cultivated. All this suggests the possibility of rethinking the concept of zonation and its methods, which could start from the finished bottle or, if you want to characterize sub-zones, from semi-finished products taken in cellar, but always produced on an industrial scale”.

A research work that has among its results a database of 1,700 volatile compounds requires in-depth studies that can still give a lot of information. Mattivi explains that the next steps will be for instance the ones that allow identifying among all the detected or identified compounds those with an actual sensory role.

Another interesting finding, to which the research here presented led, too, is explained by Fulvio Mattivi: “For the first time in sparkling wines we detected the presence of the two main flavours of saffron, that is to say safranal and a isophorone. Although for the moment we do not know if they are present in concentrations above the perception threshold, as there is no indication in the literature concerning this concentration in wine, the experience of the most experienced tasters confirms that the note of saffron is present up to be dominant in some long evolution sparkling wines. Moreover, in contrast to what is generally reported in the literature, where the described norisoprenoids are compounds with thirteen carbon atoms (C13), these new compounds are C9 and C10, and therefore derive from biochemical processes of hydrolysis which are different from the already known ones”.

The first metodo classico produced in Trentino dates back to the early twentieth century and is signed by Giulio Ferrari, founder of the homonymous winery. In 1993, Trento was the first designation of origin assigned exclusively to a metodo classico sparkling wine. This denomination from Trentino, with about seven million bottles produced on average each year, today represents 35% of national production of metodo classico sparkling wines. For further safeguard of both identity and cohesion among producers, in 2007 to this production Trentodoc collective brand added. Today it gathers 41 producers in the province of Trento. Therefore, a number of records is recorded, the last of which was the partnership signed with the Institute of Masters of Wine, the most prestigious non-academic institution worldwide dedicated to both enhancement and promotion of wines from around the world.

Article by Alessandra Biondi Bartolini

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