Last week I posed the following question to the Twittesphere and Facebook: “What comes to mind when you think of acidity in wine?” The responses were varied, some negative (sore teeth, vinegar), others positive (yes please!, the root of all good wines), others irrelevant (“LSD” is not found in wine!). So whose 140 character nugget hit the nail on the head? The truth is that acidity, an essential component of wine, can be both good and bad. When unbalanced or flawed it can make a wine overly tart or even spoiled, but when balanced, acidity can be the perfect complement to fruit, tannins and sweetness found in wine.
Types of good acid
All fruit contains acid that acts as a natural preservative. Acid is thus present in grapes, and so too in wine. Just as acid acts as a natural preservative in fruit, acidity in wine helps to maintain wine’s freshness as it ages, as well as protect wine from certain types of bad bacteria. Tartaric and malic acid are the most important acids in wine.
Tartaric acid, the more prominent of the two, maintains the chemical stability and colour of a wine, while contributing much of a wine’s tartness. Tartaric acid levels are stable in grapes, so the level of tartaric acid in a grape at the beginning of growth is the same level of acid when the grapes are fully ripened. Once fermented into wine, it’s another story, the level of tartaric acid slowly decreasing as acid crystals precipitate out of the wine. Thus over time, a wine will lose its acid, just as it loses its tannins. For a white wine to age well it therefore must have high amounts of initial acid. This is why high-acid wines from cool-climate regions like Burgundy can age so well, while low-acid wines from hot-climate regions like California should be consumed quickly.
Malic acid, the second main grape acid, gives green apple notes that are so often prominent in unoaked whites like Sauvignon Blanc and Riesling. Unlike tartaric acid, the level of malic acid decreases throughout grape ripening in a process known as respiration. Grapes have their highest level of malic acid just before veraison (the onset of grape ripening), and gradually lose malic acid as the grapes’ sugar levels rise. In cool climates like Burgundy, New Zealand and Canada, grapes ripen slowly and malic acid remains high at harvest. In hot climates like most of California, South Africa and Chile, grapes rapidly ripen to their fullest potential, malic acid either completely dissipated or dwindled to very low concentrations by the time the grapes are picked. If no malic acid remains a wine can taste flabby and unbalanced. Warm climate countries often add acid back into wine to balance flavours in a process known as acidification.
In cool climates, the high levels of malic acid can sometimes be too acidic and harsh. To mellow out the tart green apple notes, wine makers will put some of their wine (especially reds and oaked whites like Chardonnay) through a second fermentation known as malolactic fermentation (or MLF). In MLF malic acid is converted into the softer lactic acid, which has milky flavours. Oaky chardonnay’s that taste “buttery” almost certainly have gone through MLF.
The bad acid
Not all acids are created equal. Acetic acid, most often found in vinegar, is usually present in very small concentrations in wine. When too much acetic acid is in a wine it creates a fault known as Volatile Acidity, where the wine smells and tastes like vinegar. If you taste a wine with vinegar characteristics either at home or at a restaurant, send it back! Flawed wine is a fact of life and your local wine store or restaurant will gladly exchange it.
What affects acid levels: climates and grapes
Climate has arguably the greatest impact on acid: hot climates produce low acid wine and cool climates producing high acid wine.
Different grapes naturally have different levels of acid. High acid whites include Chablis (chardonnay from Burgundy), Sauvignon Blanc, and German Riesling . High acid reds include Chiati (Sangiovese grape), Barbera and Bordeaux blends.
Acid is to wine what carbonation is to soda pop. Without carbonation, a glass of Coke tastes very sweet and may even be difficult to drink. Add some bubbles and it’s much more refreshing. Acidity in wine has much the same effect in sweet wine. A sweet wine without acid is overwhelmingly sweet on the palate and too syrupy to enjoy. However, this exact same wine balanced with high levels of acidity will taste sweet, but refreshing. The sweeter the wine, the higher the acid levels should be. There is a misconception that off-dry or sweet wines are less desirable than dry wines, but the truth of the matter is that our palates tell a different story. Just as so many of us love sweet foods, we also love the taste of sweet wines. Sweet, high-acid wines like many German or Alsatian Rieslings provide the sweetness we love, with a backbone of refreshing acid that makes the wine so delightful.
Acid and Food
In Europe, where wine has always been an essential part of any meal, wine is made to be drunk with food. As a result, many European wines (i.e., Italian reds), have high acid levels to stand up to acidic foods like tomato sauces. Acid in food smoothes out the acid in wine, and can transform a wine that initially seems too tart into a delicious pairing. So next time you have a wine that tastes too tart, make sure to pair it with acidic food before tossing it.
Let’s end with an experiment. Take a wedge of lemon and suck on its juices. Notice the sensations on your tongue and in your mouth as you bite down and after you have finished tasting. From memory alone you can feel your tongue prickle and water from the acidic lemon. Acid in wine has the same mouth-watering zip of a lemon slice. It is refreshing and palate-cleansing. Just as you would reach for an icy glass of acidic lemonade on a hot summer’s day, the same refreshing acidity is found in a cool-climate Riesling (i.e., from Germany) or a Burgundian Chardonnay (Chablis). Beyond its refreshing effect, acid also adds complex layers of flavour to a wine, balances sugar and tannin levels, and enables white wine to age.
Nicole is a wine blogger and all around wine worker bee at Lifford Wine Agency, Ontario’s largest supplier of wine to the province’s hospitality industry and the number one supplier of fine wine to the L.C.B.O. Wine Decanted is a bi-weekly column about wine. You won’t find tasting notes or scores here. Instead she’s taking the hot air out of wine writing and giving us tips for folks who just want to learn more about the good grape.
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