If you’ve ever smelled strange aromas in wine, it’s likely you’ve already learned how to identify different classes of aromas. For example, the smell of a fresh cut green bell pepper, or even the smell of gasoline. There are well over a hundred individual aroma compounds in wine that interact with each other to create thousands of potential smells. As complex as the science of aromas is, there are a few well-known compound classes, often referred to as “impact compounds,” that are prevalent in certain wines. Next time you try one of the wines below, try to identify each smell!
VIDEO: Master Sommelier, Matt Stamp, offers insight on how expert tasters use their knowledge of impact compounds to blind taste wine.
6 Impact Compounds To Know
Smells Like: Bell Pepper, Fresh Cut Grass, Green Peppercorn, Asparagus, Pea, Earth
Wines: Cabernet Sauvignon, Merlot, Malbec, Carménère, Sauvignon Blanc, Cabernet Franc, etc
Pyrazines are most commonly associated with Bordeaux-origin varieties. In red wines, it’s often a touch more difficult to sense and can sometimes be associated with a raw cocoa or dark-chocolate like aroma. Most wine drinkers find this compound class to be positive in white wine but negative in red wine. In fact, Robert Parker of the Wine Advocate systematically rates Bordeaux and Napa wines lower if they have noticeable methoxypyrazine. Interestingly enough, as red wines age, pyrazine seems to lose its edge revealing cherry and chocolate-like notes in red wine.
There are 3 primary methoxypyrazines which contribute “vegetal” aromas: 2-methoxy-3-isobutylpyrazine (IBMP) giving earthy, grassy, and green bell pepper aromas; 2-methoxy-3-isopropylpyrazine (IPMP) giving aromas of asparagus, peas, and earth; and, 2-methoxy-3-alkylpyrazine with gives roasty and nutty aromas. Matt Kirkland, M.D. winescholardguild.com
Smells Like: Black Pepper, Marjoram, Leathery, Cocoa Powder, Earthy Spice Flavors
Wines: Syrah, Grenache, Zinfandel, Petite Sirah, Grüner Veltliner, Schioppettino, Mourvèdre, Pelaverga, etc
This compound is the key ingredient in black and white peppercorns and is about 10,000 times less prevalent in wine. Still, human sensitivity to this compound is quite high so it plays an important role in the flavor profiles of the wines that contain it. This is the impact aroma that gives red and white wines a spicy taste.
Smells Like: Rose, Flowers, Sweet Fruits, Mandarin Orange, Coriander, Sweet Spice
Wines: Gewürztraminer, Viognier, Riesling, Albariño, Muscat Blanc, Schiava, Torrontés, Cotton Candy Grapes etc
The more pronounced monoterpenes include the compounds of Linalool, Geraniol and Nerol. These are the same aroma compounds used to create sweet-smelling perfumes, soap and shampoo, so it’s no surprise that some people might describe these wines as having a “soapy” smell. What’s interesting about these aromas is unlike the other compounds, you can taste these in raw grapes.
Smells Like: Cumin, Maple Syrup, Walnuts, Molasses, Roast Tobacco
Wines: Found in oxidized wines such as Madeira, Vin Jaune, Sherry, Old Sauternes, Old Chardonnay, very old Red Wines
This is the major flavor compound found in fenugreek seeds and lovage (a very unique green herb). In wine it comes from oxidation and most prevalent in fortified wines like Sherry and Madeira. You can also taste it if you age a white wine for about 7-10 years–this aroma is a intriguing thing to look forward to identifying when trying old wines.
TDN (aka 1,1,6,-trimethyl-1,2-dihydronapthalene )
Smells Like: Kerosene, Petroleum, Diesel Fuel
Wines: In many varieties (Sauvignon Blanc, Chardonnay, etc) but most noticeable in Riesling
This aroma is one of the few aroma compounds that is almost non-existent in grapes and increases in wine as it ages. The wines noted with the strongest petrol-like aromas come from warmer vintages as the compound develops as grapes are exposed to sunlight.
Smells Like: Butter, Cream
Wines: Wines that have undergone Malolactic Fermentation (Red Wines, Chardonnay, Viognier, etc)
This compound is much more pronounced in white wines, but adds an aspect to red wine that’s often described as creamy or velvety. Diacetyl comes from the post-fermentation process called Malolactic Fermentation which bacteria eating malic acid and pooping out lactic acid (sounds delicious right?). The result gives wine this awesome creamy and buttery aroma and texture. By the way, very few white wines undergo this process which is one of the primary reasons they taste so much different than red wines.