“Cat’s pee on a gooseberry bush” sounds less than appealing, but it’s a cliché description for Sauvignon Blanc, even among people who’ve never tasted a gooseberry (the smell of cat’s pee being more ubiquitous). I learned a more personal grape-aroma association from Greg Harrington, MS, when he was the Corporate Beverage Director at BR Guest Restaurants in New York; he described red Bandol, from Provence, as smelling “like the burnt ends of a grandmother’s pot roast.” He also said Viognier often smells like Fruit Loops. These associations may seem far-fetched, but at the time, they helped Greg pass the blind-tasting portion of the Master Sommelier exam.
The wine industry today generally favors relatively objective tasting notes over more poetic, idiosyncratic descriptions, and Harrington’s reference to pot roast would probably be transformed into “rich, meaty aromas” in print. But the idea that a grape or a region’s wines have typical, identifying aromas or characteristics is still going strong. Blind-tasting relies on it: In the MS exam, would-be Master Sommeliers taste six wines in 25 minutes, hoping to identify each wine, right down to the vintage and sometimes even the vineyard, by analyzing its aromas, body, color, etc. I’m only talking about the aromatic descriptors, though texture, body, acidity, and other factors are also part of the parlor trick. (Did I say parlor trick? I meant “Holmesian deductive process.”)
Wines don’t need off-the-wall aromatic descriptions to be typical to their grape variety or region. Cabernet Sauvignon often has an aroma of blackcurrants. Brunello di Montalcino, a touch of graphite. New Zealand Sauvignon Blanc often has aromas of passionfruit and grapefruit, or, in cooler vintages, the smell of green vegetables like peas or even grass (which is better than cat pee, at least). Of course, a single wine will have more than one aroma; Gewürztraminer is known for a giveaway scent of lychee, but tangerine, rose petal, or mandarin notes also fit the profile.
Things get much more specific. Burgundy, for example, is famous for characterizing its vineyards and their character. The wines of the village Volnay are noted for their cherry aroma, whereas Gevrey-Chambertin reveals itself with a touch of licorice. Then, within the latter village, the Latricières-Chambertin vineyard is held to yield a spicier wine, whereas Clos de Bèze is more floral. And this isn’t about different grape varieties, since all of these sites are planted to Pinot Noir.
In 1990, UC Davis professor Ann C. Noble introduced the Wine Aroma Wheel, which subdivides potential wine aromas into broad categories – fruity, floral, earthy, etc. -- and then breaks down each one into sub-categories and individual descriptors -- raspberry, rose petal, etc. Some of them are faults -- aromas only found in an improperly made or tainted wine -- but there are 87 potential aromas on the wheel. That’s conservative; most wine pros actually parse things even further -- apple isn’t specific enough; is it Granny Smith? Baked? And the wheel doesn’t even include cat pee (wet dog, however, does get a mention). Where are all these aromas coming from?
In theory, it’s simple: Aromas are chemicals. What’s surprising is how hard it can be to determine which chemical accounts for a specific aroma in a wine. Researchers have discovered some: The touch of green bell pepper that shows up in unripe Cabernet? Methoxypyrazines. Pineapple aromas in a Chardonnay? Ethyl Caprylate. (No word yet from scientists on the mysterious “grandmother’s pot roast” molecule.) But other factors can influence how or whether we perceive these aromas, so it’s not as simple as ticking off a list of chemicals present.
A small change in temperature can change our perception; that’s one reason wines often taste different than they smell -- the wine warms up in our mouth. A lot of chemical interactions also take place, during winemaking as well as during aging. For example, varying combinations of acids, which may or may not have aromas of their own, also stimulate the formation of different esters, a group of chemicals responsible for many of wine’s fruity aromas (over 160 esters have been found in different wines). In many cases higher acidity will cause the expression of fruit in a red wine to turn from dark fruit to brighter expressions, either within the same fruit type (black cherry to bing) or to different types entirely (blackberry to raspberry).
These aromas only appear after the grapes become wine because many of the relevant chemicals are bound to sugar molecules inside the grape, which renders them odorless until released by fermentation. This is one of the big differences between grape wine and wine made from other fruits; while raspberry wine tastes like raspberries and blueberry wine, like blueberries, wine made from grapes rarely actually tastes grapey. The other big factor is the wine grape’s balance of sugar, acidity (especially tartaric acid, which is rare in other fruits and particularly resistant to bacteria), and yeast nutrients; grapes, more than other fruits, lend themselves to making a stable wine.
As for diversity, it’s not really that surprising. It seems the varieties used today were selected from wild vines a long time ago, so they’ve had quite a while to grow apart and distinct; we’ve been making wine for at least six millennia, and probably longer. If we can breed dogs into St. Bernards, Chihuahuas, and Greyhounds, it’s not all that amazing that we got some variety out of something that doesn’t run away when it’s off the leash.