Wine Terms, Explained: Understanding Acid and Tannin in Wine
Learn about the "bones" of wine.
Four fundamental traits make up the building blocks of wine: alcohol, sweetness, acid, and tannin. Sweetness and alcohol are traits that pretty much everyone who's raised a glass can easily understand, but acid and tannin are what gives the wine its structure. If sweetness and alcohol are the flesh of a wine that provides the flavor, acid and tannin can be considered the bones: the core of a wine that supports everything else. They can both be detected as sensations you can feel on your palate.
Acidity in Wine
Most wine of quality is on the lower end of the pH scale: between 3 and 4 (for comparison, vinegar is around 2.5 and water is a 7). When a wine has a low pH, it means there's more acid present, and acidity is an excellent thing for wine. It's difficult for microbes and bacteria to survive in an acidic environment. There are three main types of acids in wine—tartaric, malic, and citric—and each has slightly different flavors. You will know a wine is high in acid when you sip it and your mouth has a natural reaction: It quickly starts producing saliva (a sommelier trick to blind tasting). Wines with high acidity feel crisp, zesty, or tart on the palate with a puckering sensation, where low acid wines have a smoother, rounder mouthfeel. Whether you enjoy high acidity is a personal preference; some people prefer a zesty vinaigrette dressing, and some prefer a creamy ranch.
Wines from cooler climate areas tend to have higher acidity. When grapes are under-ripe and green, they are naturally tart and high in acid. As grapes get riper, the sugar and pH levels rise, and the acid drops. Cooler areas with cold nights during the growing season allow grapes to retain their acidity. Generally speaking, you can expect a wine from a mountaintop in Germany to have higher acidity than a wine from a warm valley area of California. In terms of food pairing, salt and fat balance out the tart sensations of high-acid wines, which is why it's such a great idea to pair a high acid wine like Champagne with salty, fatty foods like Salted Buttermilk Fried Chicken and French Fries.
Tannin in Wine
Tannin is a compound in wine that's naturally occurring in the seeds, stems, and skins of grapes (it's also found in bark, wood, and leaves.) The term tannin came from the ancient Latin when tree bark was used for tanning leather. When tannin hits your tongue, you will immediately feel a rough sensation where it feels like your tongue feels dry, accompanied by a sandpaper-like texture. Some tannins are very harsh and aggressive, while some are milder and more velvety. Aside from wine, there's a lot of tannin in dark chocolate, nuts like almonds and walnuts, whole spices like cloves or cinnamon bark, and tea leaves. If you want to experience tannin in a very pure form, over-steep a bag of black tea to feel that tannic sensation when you take a sip.
Tannins are natural antioxidants, so they can help protect and preserve the wine as it ages—and harsh young tannins tend to mellow and integrate nicely into the wines as time goes by. Red wines have more tannins than whites because reds use the skins (where much of the tannin polyphenols live) as part of the winemaking process, but white wines do not. Red grape varieties that are naturally high in tannin include tannat, nebbiolo, sagrantino, cabernet sauvignon, and syrah. A winemaker can craft wine to minimize the presence of tannin, so the actual sensation of tannin will depend to a good degree on the style of the winemaker. Mass-produced wines that are meant to be drunk without bottle age are often created to have rounder, smoother tannins to make them friendlier and more accessible to wine drinkers.
Tannin is an excellent thing to have in a glass of wine when it comes to food pairing because the tannin molecules can bind onto proteins and help clean them off your tongue, keeping your palate refreshed and ready for more food. The most classic pairing for tannic reds is red meat. Try Grilled Strip Steak with Herb Butter, Beef Bulgogi, or Miso-Tomato Braised Short Ribs.