Fernando Buscema has been asking the same question for over a decade: Can terroir be measured? The Bodega Catena Zapata winemaker and director of the Catena Institute of Wine, an Argentine enology research program, hoped that answering it could raise the stakes for the wines of Argentina.
A new study, published in Nature's Scientific Reports journal in February and led by Buscema's colleague and fellow winemaker Roy Urvieta, using techniques Buscema developed, suggests that it's possible to identify the vineyard from which a wine comes based on the wine’s chemical components. In other words, terroir can be quantified.
Establishing a terroir control group
The study defines terroir as an "interplay of factors, which include the vine and its physical environment, together with the human managing the vineyards and wineries." It’s an old concept, born in France, where Burgundian winemakers who worked the same land over a lifetime passed down their knowledge of what a certain parcel of land could or should impart to grapes and finished wine.
Urvieta, who is now the winemaker at Catena Zapata co-proprietor Dr. Laura Catena's Domaine Nico, and Buscema didn't have 800 years of experience in New World vineyards, so they used science to catch up. When Buscema arrived at the University of California at Davis as a graduate student in 2010, five years after joining Bodega Catena Zapata, he worked with enology professor Roger Boulton to theorize if and how terroir could be measured. Boulton recommended focusing on Malbec. The results of Buscema's U.C. Davis research were published in Food Chemistry and the American Journal of Enology and Viticulture, in 2014 and 2015, respectively.
The 2014 study set up a framework for understanding Malbec's variation. Buscema and Boulton took 41 Malbecs, 26 from vineyards in Argentina (Luján de Cuyo, Maipú, Tupungato and San Carlos) and 15 from California (Lodi, Monterey, Napa and Sonoma). Every wine came from the 2011 vintage. Their team measured aroma compounds (also known as volatiles) and chemical parameters such as pH, alcohol and sugar levels. A tasting panel also conducted a sensory analysis.
The results highlighted key regional differences between Malbec from California and Argentina, along with local differences within appellations. But a question remained: Were those differences a product of the vintage, or the soil?
Eliminating the vintage variable
The 2014 study led Buscema and his team to develop a model to use in further investigations. By measuring three components—phenolic compounds, volatile compounds and sensory profiles—they hypothesized that wine from any vineyard could be identified by a vinous “fingerprint.” Buscema says that researchers are now using this model to study Shiraz in Australia, Pinot Noir in California and Cabernet Sauvignon in Chile.
Enter Catena Institute PhD student Roy Urvieta, who in 2018 worked on a multi-part graduate thesis by evaluating more vineyards in Mendoza using Buscema's model. Initial findings, which validated the 2014 study, were published later that year in Food Chemistry.
"We wanted to know if this model was good [across] vintages," Buscema said. "So with Roy we proposed a second chapter of this project that studied the model in different years and small parcels, and the model worked perfectly."
Funded in large part by the Catena Institute and conducted in cooperation with Argentine government agency CONICET, Urvieta's study used high-performance liquid chromatography to evaluate phenolic profiles of Malbecs from 23 sites representing 12 Mendoza subregions, each site selected based on homogeneity of soil, minimum vine age of five years and consistent vineyard management. In total, 201 wines from three recent vintages were studied.
Urvieta and his team measured for 27 volatile and phenolic compounds responsible for factors like mouthfeel and color, including resveratrol, quercetin, caffeic acid and tyrosol; the results showed that many parcels could be correctly identified independent of vintage. Out of the 23 vineyard parcels studied, 11 could be identified with 100 percent accuracy, while the remaining 12 were ID'd with up to 83 percent certainty. Wines from the Rivadavia subregion and Uco Valley’s high-elevation Gualtallary subregion proved easiest to identify.
But Buscema’s model also calls for a human metric, so he recruited blind tasters in Davis, Calif., and Buenos Aires and Mendoza in Argentina. "We measured all the characteristics a human could perceive in these wines to see if there were characteristics unique to a parcel and [whether or not the panelists] distinguished it," Buscema said. "I think that was the most interesting thing we found in this path."
Buscema and his team didn’t trust phenolics and volatiles alone, and the sensory panel serves to make terroir easier to explain. "I can say a wine has a high level of glucose and certain elements, but for a majority of people, that doesn't mean anything," he said. "But if I say, 'This parcel will have elevated violet aromas and a smooth palate and lots of concentration,' it's much more trustworthy."
Buscema and Urvieta’s research has raised new questions, and they hope to expand their findings. Urvieta is curious about returning to the study in a few years, since older wines may develop a clearer terroir fingerprint.
"If I do the same analysis in a few years, where now you have more aging, we can distinguish much better because the wines are going to differentiate from each other even more," Urvieta theorized, suggesting they might learn “what the chemical or sensory markers are that make a wine age better."
According to University of Adelaide’s Global Wine Markets, 77 percent of the world's Malbec production comes from Argentina. Buscema, Urvieta and their team of researchers hope that understanding Argentina’s soils will help winemakers elevate the quality of Malbec and catapult its reputation.
And there are farther-reaching applications. Terroir fingerprints could be developed all over the world, helping viticulturists and winemakers better understand their vineyards. The ability to identify the vineyard source of a rare wine could also prove to be a powerful tool in identifying counterfeit wines.
"This will allow regions that aren't traditionally of highest quality a chance to show, not in centuries, but in years, that they have something unique in their terroir," Buscema said. "We are not trying to say better or worse, but rather this is distinct and we can measure it."
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