I teetered on top of the enormous tractor, careful not to lose my balance as it shook from side to side. The vibrating machine hovered over a single row of vines at a time, shaking their perfectly ripe grapes free into the large bins below. I turned around to glance into the dark rows of vineyards lit only by the moon above.
“Why are we harvesting the grapes in the middle of the night, again?” I asked over the roaring sound of the tractor. “Is everyone here just nocturnal?”
“No, not exactly,” said Juan de Benito Ozores, director of the Alvarez y Diez winery, who was seated beside me. “You see, the fresh juice from the grapes, it would oxidize too quickly in the heat. We don’t want them to lose the perfect sugar and acidity levels they have right now.”
It was just past midnight in Rueda, a small white wine-producing region just a two-hour drive from Madrid. Though the timing was a bit odd to me, I had ventured there to watch the winery’s annual grape harvest, which started at ten o’clock at night and would finish just before sunrise.
All of the other wineries I had visited in the nearby Toro and Ribera del Duero regions that week were picking their red tempranillo grapes during the day. But the harvest’s late start time wasn’t strange for the workers here in Rueda. It’s not uncommon for verdejo and sauvignon blanc — the white grapes grown in the area — to be harvested late at night, when the temperatures are much cooler. If picked during the day under the hot Spanish sun, the grapes risk ripening too quickly before arriving at the winery to be pressed, compromising their balanced levels of natural sugar and acidity.
Even with a limited background in chemistry, I knew the importance of sugar in winemaking well enough. Without it, you cannot possibly produce wine. It’s what gets converted into alcohol during the fermentation process, transforming grape juice into a boozier beverage. But I wasn’t so confident about the significance of a grape’s acidity levels. Before witnessing the harvest in Rueda, I had been fixated on the big, bold reds of Spain, and because acidity is more prevalent taste-wise in white wines, didn’t fully grasp why it was equally as vital.
“Without the right acidity,” said Ozores, “you cannot make a very desirable wine.” It is a crucial component in any wine, but especially in whites. Acidity is to white wine what tannins are to red wines — it serves as a backbone. It livens up a wine and brings all of its flavors together, making it taste fresh and youthful. It also acts as a preservative, helping white wines, like riesling or pinot gris, age gracefully over many years. And even more importantly, acidity kills off any harmful bacteria in wine that would otherwise make it unsafe for you to drink.
When trying to describe a wine’s acidity, the common words you’re used to using for aromas and flavors don’t work. Acidity is not something that you can smell. It’s not something that you taste, either. It’s something that you must feel. When you drink wine, you perceive acidity on the sides of your tongue, usually as a prickly or puckery sensation, which can be difficult to put into words.
But after you get the hang of it, identifying acidity in wine isn’t all that hard. If you’ve ever tasted any citrus before — a lemon, lime, orange, or grapefruit — then you certainly know what acidity feels like. The essence of the acidity in these citrus fruits can be found in wines as well. It can be fresh, puckery, bright, or racy. It might feel firm and crisp, or leave a tangy sensation in your mouth. And the acidity in any beverage is exactly what makes it so refreshing to drink.
Unlike tannins in red wine, which typically cause a drying sensation, acidity makes you salivate, which is why more acidic wines are such great matches with meals. The interaction between acids in the wine and the chemical compounds in your food makes your mouth water, leaving you wanting to take another bite, and then another sip, until both are completely gone.
A wine’s acidity needs to be in balance with all of the other elements in a wine, like its sweetness, alcohol content, or tannins. If a wine has too much acidity, it’ll taste too sour and tart. But without enough, it will be too flat, flabby, and unexciting.
There are, of course, some wines that are just naturally higher in acidity than others. Riesling and sauvignon blanc are two highly-acidic grapes, and a sip of either should always make your mouth pucker up a little. Albariño from Rías Baixas in Spain is also notably higher in acidity, and is one of my favorite go-to wines for that crisp, refreshing feeling. Other white grapes that are lower in acid, like viognier and gewürztraminer, will feel smoother on the palate and can be more challenging to pair with certain dishes.
Differing terroirs play a role in how much acidity a wine will have, too. More acidic grapes are generally grown in cooler climates, where grapes tend to ripen slower, without high levels of sugar. Places like the Mosel or Rheingau in Germany, Sancerre in France, or Italy’s Alto Adige region are all ideal places to grow more acidic white grapes. In a warmer area like Rueda, winemakers have to work harder to maintain the perfect levels of acidity in their grapes, and be extra cautious when choosing the right time to pick them.
You don’t need to find a harvesting machine to ride in order to delve deeper into acidity in wine. Just like learning about any other aspect of wine, all it takes is a little practice, and a lot of tasting. Gather any of the chosen bottles below and get those lips puckered.
I’ve selected a handful of bottles that will leave your tongue tingling and mouths watering. Riesling, sauvignon blanc, and albariño are all grapes with notably higher levels of acidity. These crisp and refreshing sips make for a great introduction to acidity in wine, and can be enjoyed on their own or alongside a meal.
Mosel, Germany, 11.5% ABV, $11.99
A great introduction to the acidic riesling grape. Very aromatic with white flowers and dark stones on the nose. White peaches and lime in the mouth, with vibrant acidity that lingers.
Alto Adige, Italy, 12.5% ABV, $17.99
Not much riesling is grown in the cool-climate alpine region of Alto Adige, but this one is especially fresh and full of puckering lemony acidity. Its refreshing finish leaves you wanting another sip.
Martinborough, New Zealand, 12.0% ABV, $13.99
Brightly aromatic with hints of grapefruit, green apple and wet stones on the nose. A white wine that is as fresh and juicy as it gets, with mouthwatering acidity and crisp lemon flavors.
Dry Creek Valley, California, 13.5% ABV, $14.99
Full of grapefruit aromas and flavors, this sauvignon blanc has bright acidity, but feels rounded on the palate. A wonderful wine for summer sipping.
Rías Baixas, Spain, 12.5% ABV, $17.99
From the coolest area of the Rías Baixas region, this albariño is intensely aromatic with hints of chalky powder and ripe melon. It’s salty and tangy in the mouth, but totally balanced, with a finish that lasts forever.
Rías Baixas, Spain, 12.5% ABV, $14.99
Delicate, with hints of fresh green herbs, ripe pears, and a bright minerality, this crisp and briny albariño is great on its own, but tastes even better alongside food.
Illustration by Claire Jelly