Let’s talk about acid. No, gentle reader, I’m not referring to that time you saw Pink Floyd back in 1977, when you thought your face was melting and the cat could hear your thoughts.
Instead, I am referring to the amount of acidity in wine, which is crucial part of producing a balanced tipple.
To ensure we are all on the same page, let’s have a brief review of why wine tastes the way it does. The primary acids in wine are malic acid and tartaric acid, both of which are naturally occurring in all grapes.
Tartaric acid is crucial to wine, as it lowers the pH balance to a point where nasty bacteria cannot thrive, which prevents the wine from spoiling. As you might have guessed from the name, tartaric acid is a big part of what contributes to the tartness of a wine.
If you have ever seen the so-called wine diamonds form in a bottle of wine, these are tartrate crystals that have come out of solution after the wine was bottled. Tartrate crystals are transparent in white wines, or stained the same colour as a red wine.
The chemists in the audience may recognize wine diamonds by their official nomenclature of Potassium Bitartrate, also known as the Cream of Tartar ingredient commonly used in cooking.
If you see these crystals in wine, just filter them out or decant the bottle, making sure to leave the tartrate crystals behind in the bottle. Don’t worry if you miss a few, as they do not affect the taste of the wine, and are safe to consume.
The other significant acid in wine is malic acid, which you may recognize as the primary flavour in green apples. So, when a wine snob tells you that an unoaked Chardonnay has notes of green apple, what they are really saying is that the wine has a lot of malic acid.
Malic acid bestows a fairly tart flavour into wine, which is preferred in highly acidic wines like Sauvignon Blanc, but perhaps less so with a Merlot.
Fortunately, malic acid will naturally degrade into lactic acid (the main acid in milk), which softens the flavour and lowers the perceived acidity of the wine.
Many winemakers will intentionally induce malolactic fermentation by introducing lactic acid bacteria to the wine after the primary fermentation. This process is followed for nearly all red wines, as the softer and rounder mouth feel generally goes better with oak aging.
Malolactic fermentation is not as commonly used for white wines, as the crisp acidity and flavours of green fruits are more prized in white wines.
The smoother flavour profile of lactic acid is generally preferred in red wines, which imparts a buttery or creamy finish.
The amounts of tartaric acid and malic acid in a particular grape depends on many factors, including the grape varietal, ripeness, climate, and other environmental factors. A good rule of thumb is that cooler climates produce more acidic wines, while hotter climates produce riper grapes with lower acid levels.
Since winemakers cannot control the climate, they can control acidity by harvesting the grapes earlier or later in the season, or choose the more common option of adjusting the acidity during the winemaking process.
A wine can be made more acidic by mixing in some powdered tartaric acid, or made less acidic by precipitating out the tartrates with cold stabilization. Most winemakers use one of these methods to tweak the flavour profiles for consistency from year to year, or to adjust for the vagaries of climate.
Different grape varietals will have different natural acidity levels, which is a major component of the flavour of the wine, and people tend to prefer specific wines for their particular acidity level.
For example, if you like Riesling, Sauv Blanc, or Pinot Noir, you probably enjoy highly acidic wines.
Medium-acidity wines include Chardonnay, Merlot, and Cabernet Sauvignon. Unsurprisingly, this middle-of-the-road acidity makes up most of the mass market.
Low-acidity wines are less common, and would include varietals such as Viognier and Tempranillo.
Whatever wine happens to be your favourite, the level of acidity must be balanced with the fruit flavours and tannins for the wine to be enjoyable. Try a few different glasses on your next night out on the town to see how each wine contrasts with the others!
