Wine Basics

Everything You’ve Ever Wanted to Know about Acidity

Although we may not spend much time thinking about it, acidity is actually present in every refreshing beverage we drink, from Coca Cola to coffee to milk. In wine, it’s a very important structural component, and is needed not only for your immediate enjoyment while tasting, but also for aging if you want that bottle to stay fresh for years to come.

So, what exactly is Acidity?

Acidity, in it’s most basic terms, it the total amount of acids that are present in a liquid. There are a few different ways to measure this:

We can measure it as a percentage of the total volume of liquid, for example. In wine, we want the acids to account for between 0.6 to 0.75% for dry wines, and 0.7 to 0.85% for sweet wines. Below 0.6% will make the wine taste “flabby”; it’s lacking that much needed zip that keeps it fresh. But when we get into the higher end, things can start to taste unpleasantly tart and sour.

We can also measure acidity using the pH scale. If it’s been a while since your high school chemistry classes, here is a refresher: the lower on the pH scale, the higher the acidity, and vice versa. Wine falls in the neighbourhood between 3 and 4. To give you some real life comparisons, lemonade and Coca Cola sit around the 2.5 mark, coffee sits between 4.5 and 5, and milk is way up there at 6.7. We hit neutral (ie. water) at 7.

There are also different types of acids that contribute to the total amount of acidity. The primary types comes of the grapes themselves, and include Tartaric acid, Malic acid, and Citric acid. Several other acids are then produced during the fermentation process, including Acetic acid, Carbonic acid, and many others. We will get more into these later.

Acidity in the Vineyard

Where do these acids come from? Most are naturally occurring in the grapes themselves, so let’s start with those.

When a grape first starts to develop, it has it’s highest acidity (about 3%), and it’s lowest sugars (about 4%). As it grows, that balance shifts, and the acidity decreases (to about 1%) and the sugars increase (above 24%). The winemaker needs to try to harvest the grapes when they are deliciously sweet but haven’t lost that very important acidity.

The level of acid in the grapes is also dependent on several factors and can vary quite a bit.

For example, each grape varietal has a predisposition to it’s own range of acidity. Grapes like Riesling and Cabernet Sauvignon are naturally higher in acid than grapes like Gewurtztraminer and Grenache.

Then we have the soil that the grapes are grown in. Different soil composition contributes different nutrients, and therefore different acidity levels as the vine grows. Potassium-deficient soils, in particular, tend to produce higher acid grapes.

And finally we also need to consider the overall climate of the region and it’s temperature within each growing season. Cooler regions produce naturally higher acid wines than warmer regions. But a particularly warm year in a cool region will reduce that natural acidity, and vice versa.

Acidity in Winemaking

As mentioned above, a big part of the winemakers job when it comes to achieving a balanced wine, is picking the grapes at just the right time.

There are a few other tools in the winemaker’s toolbox though that can also have a powerful effect on how that acidity is going to come across in the glass.

It can be as simple as adding acidity to a wine that is lacking, which is done most commonly in warmer growing regions. A wine can also be “deacidified”, but this is much less common.

My favourite of these tools is a process called Malolactic Fermentation, also known as Secondary Fermentation. This is a naturally occurring biochemical reaction that the winemaker needs to prevent if they want to keep their lighter white wines tasting fresh and zippy, but is typically allowed to occur in all red wines and some more powerful whites.

In this process, bacteria converts malic acid into lactic acid and carbon dioxide. The resulting lactic acid is much softer on the palate than malic acid, as we will discuss later. It makes the wine smoother and softer, and adds a buttery flavour to the wine.

Sounds yummy right? So why don’t we do it for all wines? Well, for some of those lighter wines, their flavours and aromas are so delicate that they would become overpowered, and lose what makes them beautiful.

Want a tasting experiment to see what it’s all about? Try an Chablis alongside a California Chardonnay. The Chardonnay grapes used in Chablis are incredibly high in acidity due to their cool climate, and malolactic fermentation is stopped before it can begin. But California is a much hotter growing region, and then goes through the malolactic fermentation process and oak to create rich, buttery smooth flavours and mouth-feel. They are wildly different!

Acidity in Wine Ageing

Acidity also plays a key role in providing the structure that an excellent wine needs in order to sit on a shelf for the next ten years, as well as warding off harmful bacteria that can cause the wine to spoil.

You need a nice high baseline of acidity in your wine to start if you are planning to age it. This is because the acidity will soften over time. If it starts off too low, that acidity will be completely flat by the time you are ready to open the bottle. That’s why Rieslings are a favourite of white wine collectors.

For reds, a bottle worth aging is going to be high in both acids and tannins when they are first produced. That’s why so many of them don’t taste great in their youth – because your palate is so busy with those two components that it can’t quite perceive the fruit qualities it possesses. Over time, the acidity and tannins will both soften, and that fruit can come forward and really shine.

In addition to softening, acids also transform in type as they age. The end result is acetic acid, which is essentially vinegar on your palate. You don’t want your wines to sit so long they taste like that!

Tasting Acidity

So with all that said, let’s talk about how you will actually taste acidity on your palate while sipping your next glass (preferably on a warm patio!).

Here are some descriptive terms to get you going:

• “Flabby” or “flat” wines are distinctly lacking in acidity
• “Well-balanced” wines are even across the board when compared to the other major wine components
• “Fresh” or “crisp” wines have slightly higher acidity, but it doesn’t overwhelm the fruit flavours
• “Taut” or “austere” wines are a little higher, and less fruity, more serious
• “Tart” and “sour” wines have too much acidity to be enjoyable
• “Acetic” wines have gone into the region of vinegar

One of the ways acidity shows up is as a tingling or puckering sensation on your tongue and gums. Each person detects it somewhere different depending on how they drink, so pay close attention to where you feel it most.

Try thinking about sucking on a lemon for a few seconds. Really visualize it. Did you feel that visceral response in your mouth? Just thinking about high acidity makes our body want to brace for it! That’s the feeling you are looking for when you taste.

The trick with this, however, is that tannins can have a similar effect, and sugar in wine can help disguise the effects of acidity. It sometimes confuses new wine tasters into thinking a wine is extremely tannic or dry, when really it is just highly acidic.

The other way to assess acidity (which I find much more reliable) is by it’s mouth-watering effects. When something is high acid, our mouths respond by producing saliva to water it down. Try taking a sip of wine, and after you swallow, let your mouth sit and see how long it takes to fill with saliva. I know, it sounds a bit gross, but it’s a great indicator of the level of acidity in your wine!

I also want to return to those different types of acids for a moment, because they each play a role in affecting the flavour of the wine. There are lots of different types, but we will cover off the ones you are most likely to notice while tasting:

• Tartaric acid is found in bananas and cream of tartar; it is the main acid present in grapes, and it responsible for crisp flavours and aging potential
• Malic acid is found in apples and gives wine powerful fruity flavours
• Citric acid is found in lemons, limes, grapefruits and oranges and makes wines extra zippy
• Lactic acid is found in milk and gives wine a much softer, rounder mouth-feel
• Carbonic acid is found is fizzy drinks like pop and is a key player in sparkling wines
• Acetic acid is found in vinegar and is the least desirable

Finally, we can also use our sight to give us a hint as to the level of acidity in a wine before we even taste it. This only applies to red wines, however.

The pH level of a red wine affects the hue of red that we see. Wines lower on the pH scale (and therefore higher in acidity) appear more red, whereas wines higher on the pH scale (lower acidity) appear more blue or purple. Neat trick, huh? Try it out next time you’ve got two different glasses of red in front of you.

As temperatures warm up, are you ready to dive into some high acid wines the keep you refreshed? Let me know your favourites in the comments!