Conservation of 87Sr/86Sr During Wine-Making of White Wines: A Geochemical Fingerprint of Geographical Provenance and Quality Production

Abstract

The measuring of 87 Sr/ 86 Sr in wine, grape, and bioavailable soil fraction samples with the same uncertainty of geological materials allows fully comparing the whole wineproduction chain with the peculiar geochemical isotope signature of any geographic area. Indeed, this signature is the same as the final product inherited by the soil bioavailable fraction and, in turn, by the geological substratum of the vineyard. On the other hand, the few data available in literature that referred to white wines cast doubts for the use of this geographic tracer due to the common use of geological derived additives, such as bentonite, in the white wine-making procedure, which may overprint the original geochemical signature of the vineyard substratum. To tackle this issue, we analyzed the Sr-isotope compositions of four white wines produced over a period of almost 10 years in a high-quality organic farm, located on the volcanic units of the Vulsini Volcanic District (southern Tuscany, Italy). The 87 Sr/ 86 Sr values of rock, soil, grape, grape juice, must, and wine were compared among them and further weighted against the isotope fingerprint of the bentonite and yeast employed during the winemaking process. The 87 Sr/ 86 Sr values from the entire white-wine production chain reveal that no variations are observed from the signature imprinted by the original geological substratum (rocks and soils), suggesting that no further contribution is given by the addition of bentonite and yeast to the white wine Sr-isotope values. On the other hand, intermediate 87 Sr/ 86 Sr compositions are found when grapes from different vineyards are used for making multi-cultivar wine blends. Indeed, the experimental data clearly show that the Sr isotope composition is maintained through the wine-making process for white as well as for red wines. Both grape and final wine preserved the isotope signature inherited from the labile fraction of the soil where the vines are farmed. Our data thus confirm, also for white wines, the robustness of the Sr-isotope tool in studies where it is important to define terroirs and geographic provenance.

Base Cation Mobility in Vineyard Soils of the Colli Albani Volcanic District (Central Italy)

“…The elongated shape of quartz is entirely convincing of a noneolian origin and it is unrealistic, on the other hand, to image that eolian quartz choses to deposit only in the clayey soils without leucite and analcime. This information on the origin of quartz in the Colli Albani soils is of great significate for future researches focused on the traceability of high-quality wines on the basis of isotope ratios (Tescione et al 2020).…”

Strontium Isotope Systematics of Tenerife Wines (Canary Islands): Tracing Provenance in Ocean Island Terroir

“…Wine processing is another source of potential isotopic modification agents, e.g., nanofiltration to reduce the ethanol content, the addition of bentonite (a smectite clay) to 'clear' wines of proteins and ageing in wood barrels for flavour enhancement [18,41,42]. Multiple studies of these techniques have concluded that the isotopic signature is preserved throughout the process, from soil to grape through to the finished product.…”

“…This is reinforced in Tenerife DO wines. Bentonite fining agents have high Sr concentrations, e.g., 59 ppm [41], and are added to white wines, so they may show a clay influence in their Sr signatures. Tenerife white wines have lower Sr concentrations (generally < 1 ppm and smaller ranges) than red wines in all five DO regions.…”

“…Tenerife is also distinct from other global wine-producing regions because of the relative difference between 87 Sr/ 86 Sr in the wine and that of the local rocks and substratum. 87 Sr/ 86 Sr has been repeatedly proven as an accurate tracer for wine provenance across Europe [17,40,41,49]. In other locations where vineyards are grown on volcanic terrain, 87 Sr/ 86 Sr from the local geology matches those from the wine because soils are fairly uniform and have not had time to develop differential weathering, etc.…”

Evaluating the Chemical Hazards in Wine Production Associated with Climate Change

“…Moreover, bentonite treatments are responsible for various elements deposited in the wines [ 25 , 28 , 29 ]. The geographical traceability of wines was investigated using different methodologies on the basis of multivariate analysis of natural chemical composition data (inorganic or organic parameters) and the 87 Sr/ 86 Sr isotopic signature [ 30 , 31 , 32 ]. Tracing sources of heavy metal pollution from wines is widely used as a pollution tracer, especially in the case of lead, which is recognized as a severe threat to human and terrestrial environmental health.…”