NorthBay biz Wine
The Science of Terroir
October, 2016 Issue
Terroir. Is it for real?
“Terroir” is one of the most controversial words in the vocabulary of wine. For many, it holds within the ultimate meaning of wine, whereas for others, it represents an overused marketing tool with roots in mysticism and pseudoscience. Regardless of your position—and precisely because of the fervor surrounding it—terroir is a fascinating entry point into the world of wine, as well as to human physiology and psychology.
The word terroir is derived from the French word terre, meaning land or earth, and is often defined as the characteristic flavor imparted to a wine by the environment in which it’s produced. The concept of terroir within wines goes back at least to the ancient Greeks, whose wines were labeled based on their origin, with certain regions revered because of the quality of the wines they produced.
Later, in France, the Benedictine and Cistercian orders of monks cultivated grapes throughout the church’s vast landholdings in Burgundy, conducting large-scale studies to determine the influence of various parcels of land on the wines they produced. Eventually they established the boundaries for many of the Grand Cru vineyards that still exist today. Their work formed the basis of France’s appellation d’origine contrôlée.
Although not calling it terroir exactly, the influence of a specific place on a wine’s quality and uniqueness was also captured by author Robert Louis Stevenson, whose famous quote, “Wine is bottled poetry,” adorns the gateway into Napa Valley. The full quote highlights Stevenson’s belief that certain places might hold “inimitable fragrance and soft fire,” the word “inimitable” here being used for high quality that’s impossible to copy in a different location.
“Wine in California is still in the experimental stage;” wrote Stevenson, in “Calistoga,” the first chapter of In the Valley, published in 1881. “And when you taste a vintage, grave economical questions are involved. The beginning of the vine-planting is like the beginning of mining for the precious metals: The wine-grower also ‘prospects.’ One corner of land after another is tried with one kind of grapes after another. This is a failure; that is better; a third best. So, bit by bit, they grope about for their Clos Vougeot and Lafitte. Those lodes and pockets of earth, more precious than the precious ores, that yield inimitable fragrance and soft fire; those virtuous Bonanzas, where the soil has sublimated under sun and stars to something finer, and the wine is bottled poetry: these still like undiscovered chaparral conceals, thicket embowers them; the miner chips the rock and wanders farther, and the grizzly muses undisturbed. But there they bide their hour, awaiting their Columbus; and nature nurses and prepares them. The smack of California earth shall linger on the palate of your grandson.”
Stevenson’s words remain prophetic and speak to the depth of his belief in the basic tenets of terroir: a link between a place and its wines. But what exactly is terroir and why does it matter?
Ask the winemakers
“Terroir means everything,” says Russell Bevan, owner and winemaker of Bevan Cellars
in St. Helena. “As winemakers, we’re not artists but instead caretakers of terroir, and the best wines allow for the pure expression of place. For me, terroir is a function of dirt and Mother Nature. Everything else—microbes, yeast, oak, punchdowns—is a type of manipulation and is not terroir.”
As an example of terroir in action, Bevan points to land he knows intimately. “I work with the 42-acre Tench Vineyard in Oakville,” he says. “Our fence borders both the Screaming Eagle and the Rudd vineyards, which makes this a pretty high-rent district that produces fabulous wines of terroir. We have five soil types in the vineyard, each of which produces a distinctly different wine. These wines come from only three clones [7, 4 and See], and the vines are all planted on the same rootstock. The wines are vinified separately using the same techniques, yet the resulting wines are so incredibly different. The front block, with all of its rock, produces wines that are masculine and powerful, like a fabulous bass singer. Move to the red-soil block and you absolutely feel like there’s a tenor there, creating wines that aren’t as phenolic or dense in the back of the mouth.”
Bevan explains that each soil produces different effects, using terms such as feminine, noble, round and musical, all of which are driven solely by the soil.
“The climate in Oakville is perfect for growing Cabernet Sauvignon,” Bevan says. “And at our vineyard, the weather, farming, canopy management and how we make the wines are the same. But we see a dramatic difference in the finished wine—this is an example of the influence of soil. In my mind, terroir also includes weather conditions, sun exposure, slope and rain.”
For other winemakers, terroir has a different meaning, and many include a distinct flavor profile. “When I think of terroir I think of the flavor that can come from soil," says Heidi Barrett, winemaker and owner of La Sarina. "In France, there are many wines where you can taste the influence of soil, such as many of the wines of Burgundy, with vines grown in calcareous soils, but we don’t see that as often in this part of the world. It’s more about climate here. There are a few vineyards where I can taste the influence of soil here in the Napa Valley, such as our small rocky hillside Syrah vineyard in Calistoga, but that’s pretty rare.”
Some winemakers take a more philosophical approach to the concept. “Terroir is consistent with the concept of phenomenology, which looks at things in the world as perceptions,” says Bill Dyer, owner and winemaker of Dyer Straits Wine Company
in Calistoga. “Instead, we might consider looking at everything about wine in a more unified way. Consider what your whole perception is and then look at it from a different aspect. In this way, the concept of terroir is different from what you might examine from a scientific or rational point of view, where you’d try and reduce everything down to causality. Examining terroir in a phenomenological way, one doesn’t get too hung up on belief. You don’t worry so much if it’s true or not true and instead just explore the concept through your own perception.”
“Terroir is the combination of soil, climate, vine, rootstock and human intervention,” says Bibiana González Rave, owner and winemaker of Cattleya Wines
in Santa Rosa. “They’re all related, and the longer a vineyard is planted, the more unique characteristics are reflected in the wine itself. Terroir will always define the quality of the fruit produced on a specific piece of land. You can’t make a Grand Cru wine out of a village parcel. The amazing combination of all aspects of terroir have the most significant impact on the wines we make.”
“Terroir has been observed and described by so many different people, and it’s clear that one wine tastes different from another, so it’s valid to think about why that is,” Dyer continues. “It certainly includes the soil, climate and aspect of the vine to the sun, but I know some people who say there are no differences in soil. Mike Mathews at UC Davis says you can’t attribute anything in the finished wine to the soil other than its moisture-holding capacity.”
Matthews, a professor of viticulture, recently published Terroir and Other Myths of Winegrowing (University of California Press, 2016) that calls into question the validity of the concept of terroir. In the book, Matthews notes that up until the mid-20th century, the concept of terroir was often used to denote an off-putting taste, goût de terroir, and attributes the initial sharp increase in the use of the word terroir as a way to help differentiate regions within French appellations: “All concerned capitalized on the value of having an attractive story that included the regional terroir explanation for distinctive wines.”
Matthews claims that the word has been subsequently co-opted by other wine-producing regions—and even used by other food and beverage producers—as a way to sell more product: “The second situation that correlates in time with the dramatic uptick in the use of terroir is the increase in international competition in the world of wine.”
American wine critic, author and regular contributor to Wine Spectator Matt Kramer disagrees. In his “Drinking Out Loud” column, Kramer vehemently disagrees with the book’s underlying tenets: “Bottom line [of Matthews’ book]: There are no data proving that soil informs wine. Therefore it’s a shuck. Terroir is a fake. Distinctions among wines are mere public relations for which the ambiguous word terroir is conveniently invoked.
…Therefore, as wine scientists would have it, any differences we find are invalid as they’re not verifiable. So we’re seen as dupes. Myth lovers. Irrational fools.
But we’re not. Those of us who credit the existence of terroir, of its legitimacy as a metaphor for understanding the natural world, know that recognizing terroir is no more—and no less—than a way of being alert. We know that the differences we apprehend with our senses are real and far from illusory—or mythical. We know also that soil plays an informing role, in some sites more strongly and clearly than in others.”
Kramer’s passion and defense for terroir is clear, but many scientists don’t see it as so black and white.
The science of terroir
, the Peter J. Shields Endowed Chair in Dairy Food Science and Professor in the Departments of Food Science and Technology, and Viticulture and Enology at UC Davis, has been working to define at least some of the causes of regional differences in wine. “Wine is an incredibly complex medium,” he says. Mills and his colleagues are hunting the origins and causes of terroir. “We’ve been slicing and dicing terroir up into units that are measurable and quantifiable. One of my colleagues, Professor Susan E. Ebeler
, and other researchers around the world have already demonstrated a chemical regionality to wines. For example, a Malbec wine from Argentina has a certain chemical profile and is different from the same grape fermented in California. There can be many, many reasons for these different chemicals showing up in the wine, but at least her findings lead us to the concept that there are real differences at the chemical level. Professor Ebeler and Professor Hildegarde Heymann published a remarkable paper a year or so ago showing a link between that regional chemical composition and the sensory palate.”
“We’ve shown that chemical profiles can be different based on the regions that grapes are grown in,” explains Susan Ebeler, a professor and chemist at the Department of Viticulture and Enology in the College of Agricultural and Environmental Sciences at UC Davis. “This extends to volatile compounds that impact aroma; nonvolatiles that impact taste, mouthfeel and color; and elemental profiles.”
The chemical differences between regions are detectable and may allow wines to be verified as authentic to a region in the future, she continues. “The chemical composition impacts sensory properties, so by understanding how different factors (such as growing region or viticultural impacts) impact the chemical composition we can also begin to understand the effects on sensory properties. In addition, by understanding the chemical profiles we can begin to develop methods to authenticate the wine (that is, confirm that a wine labeled as being from a specific growing region is truly from that region).”
Yet the cause of these chemical differences remains uncertain. According to Mills, one of the possible sources may be microbes, both in the vineyard and during fermentation. “Epiphytic microbes—those living on the surface of a plant or the grapes—and those living inside the plant have a tremendous potential to influence the growth of the plant or the flavor of the grape, for example,” Mills says. “Microbes that live both inside and outside a plant are well known to affect its health, just like microbes living on and in humans influence the health of the human.”
One of Mills’ studies looks at the microbial makeup of must (aka freshly crushed grapes) and found that regional differences also occur at this level. “Our studies have shown that small regional areas have unique patterns and populations of microbes in their must and that these differences can be less in areas that are close by one another,” Mills said. “Earlier studies, including our own, have shown that at least some of these microbes persist long into fermentation. We are continuing to explore how these microbes might correlate with flavor differences in wine.”
Understanding the origin of regional differences in wine may improve wine quality. “A tantalizing result is that we can predict wine flavor molecules from the early fermentation microbiome,” Mills said. “The research we are doing will create opportunities to predict wine flavor, to employ novel microbes to modulate wine flavor positively and, hopefully, innovate toward better-quality wines. In a more fundamental way we’re understanding the link between the environment and our food. In the future I’d like to find better predictors (biomarkers) of spoilage or bad wine—i.e., is there a pattern of microbes, besides the obvious spoilage, that converges to cause a poorly tasting wine versus a good wine.
“It’s clear that microbial populations contribute to the unique character and profile of finished wines,” said Greg Allen, winemaker and president at Dolce winery in Oakville, and a former graduate student of Mills who led efforts to collect samples for Mills’ study.
However, even the notion that native microbes play a role in terroir remains controversial, with many winemakers questioning the influence of native microbes in the finished wine. “Native yeasts only allow for 25 to 30 percent of a fermentation. After that Saccharomyces take control and dominates. And at that point any thought that other yeasts have any influence over fermentation is thrown out the window.”
“Most winemakers add some SO2 to the fermenting wine, killing off nearly all of the weak native microbes, so they don’t have any impact on the final wine,” Barrett says.
The concept of terroir is now being used in relationship to many foods and beverages, including organic vegetables for some of the country’s finest restaurants. Farmer Tucker (Taylor), Kendall-Jackson
’s resident culinary gardener and former gardener at the French Laundry in Yountville, considers himself a soil-farmer first. “We farm the soil, and that allows us to grow vegetables that are vibrant and represent a place,” says Tucker. “Terroir isn’t just a concept for grapes.”
Those comments are echoed by a broad array of terroir-related producers, from artisan cheeses and craft beers to marijuana. “Recently the idea of marijuana terroir has come into play,” wrote Aliza Kellerman in an article called “Will Terroir Turn Marijuana Into a Luxury Product
?” published in Vinepair in June 2016.
“Those who’ve been smoking for years can probably tell you how the quality of weed varies from place to place and how certain geographical areas produce consistently similar plants. They can describe how everything from soil to latitude to temperature affects the quality of the marijuana being grown and harvested.”
Given its broad application and the passion it evokes, it appears terroir is here to stay. But if you put two people together in a room, even if they might agree on the general concept of terroir, each is likely to define it differently, focusing on certain components, impacts and importance of any given variable. Given that science is just beginning to define these variables and search for links to the underlying causes of regional differences, it’s certain we’ll continue to refine our understanding of terroir over the coming years.
A working definition
I think of terroir consisting of all the elements of a vineyard site that aren’t subject to overt manipulation or yearly variation. This would include soil composition, latitude, elevation, sun exposure, contour, microclimate and the micro-biome—similar to what Bevan refers to as, “Mother Nature and dirt.” If you were able to taste a grape berry left on the vine that had fermented, that would be about as close to what I consider a pure expression of terroir as you could get.
But terroir is only half the equation for me, as there are all the yearly variations and human manipulations that go into the process of making wine. I call these elements the “personality” of wine. Within this category are vintage difference, rainfall, varietal choice, irrigation, pruning, crop-load manipulation and when the grapes are harvested. Personality here also includes winemaking choices: how, when and how hard to crush and press the grapes; stainless steel versus concrete versus wood fermentation containers; fermentation temperature; amount of maceration; new or used oak barrels; fining and/or filtering; and duration of aging, among others
Through the equation “terroir + personality,” we come to a finished wine.
I find the best wines tell a story of where they come from and how they came to be made. I love drinking older wines and thinking of the vineyards: how they were cared for by many hands and, once the grapes had been harvested and brought to the winery, how more hands worked with passion and skill to express something meaningful. These wines are profound precisely because they’re indefinable, the word “profound” having deep meaning, of great and broadly inclusive significance.
Here’s to keeping the inimitable fragrance and soft fire alive at least until our own flame fades into the terroir.