How tangible is terroir? Winemakers and wine drinkers love to discuss whether a particular patch of earth can speak through a wine. But can science actually prove such a connection?
A group of researchers at the University of California at Davis tried to do just that, and found that by analyzing the chemical composition of nearly identical wines from two different countries they could map distinct differences, creating a chemical fingerprint for two different terroirs. The findings not only add fuel to the terroir debate but may also provide a valuable tool for sniffing out counterfeit wines.
The study, led by enology professor Dr. Hildegarde Heymann and published in the journal Food Chemistry, aimed to determine if wines—in this case several Malbecs—created with identical vinification methods and aged for the same amount of time could be objectively identified by terroir. Can a Malbec from California be distinguished from one from Argentina other than by the best guesses of experienced tasters?
For the study, wines from 26 sites in Argentina and 15 in California were selected. The team tracked factors such as altitude, precipitation, growing days, rootstock, vine age and trellising systems employed. Winemaking was standardized: Fermenting juice remained on the skins for 11 days, and the resulting wine was not aged in oak. No acidification or filtration was used.
The researchers assembled a tasting panel at the U.C. Davis wine sensory lab and tracked how often tasters used 35 different descriptive attributes—words like “dark fruit,” “chocolate,” “herbal” and “viscous”—that could provide the makings of a flavor profile.
The team then analyzed all the wines with several methods, such as gas chromatography–mass spectrometry and selected ion monitoring, recording 60 individual chemical components found in the wines.
Comparing the chemical components to the sensory findings, the researchers ascertained direct relationships between smells and flavors the tasters detected and the compounds measured. The aroma of “spice” was linked with eugenol and 4-methylguaiacol. “Red fruit” was associated with α-terpinene, limonene and α-pinene. By mapping the sensory and chemical results, the scientists created a profile for each wine and terroir.
The study found a large degree of separation in flavor profiles between Malbecs from the two countries. Wine from the same country but different regions showed smaller differences. In the following chart, you can see the regions organized based on which smells, flavors and chemical components their wines contained.
Researchers' "fingerprint" for Malbec, with chemicals in small type, flavors and smells in bold and the wine's place of origin boxed
So what do these results mean? If scientists establish baselines for various grape varieties and regions, they could theoretically identify the geographical birthplace of a wine by matching its sensory and chemical signature against a database of known profiles.
The anti-counterfeiting implications are sizable. One could, in theory, tell the difference between a Pinot Noir from Oregon and, say, a similarly styled wine from Burgundy—even if the same clones and vinification methods were used. Whether or not analysts could differentiate between a Gevrey-Chambertin and a Morey-St.-Denis remains to be seen. Scientists will need to further explore just how granular the data points can get and whether factors other than volatile compounds can be included.
“The work by Dr. Heymann on the chemical basis for terroir is fascinating on a number of levels,” said Charles Curtis, a rare-wine consultant and former head of wine for Christie’s in Asia and the Americas. “If it is possible to use this technique to identify counterfeit wines definitively, then she will have done a great service for the wine industry and for wine collectors everywhere. The ultimate benefit could be enormous.”
While much work remains to identify more terroir fingerprints, the technique could prove to be a valuable tool to winemakers and might sharpen our own understanding of why wine from various soils tastes so different.