What is it?  Can you taste it?  How much acid is in wine? Is it necessary to have acidity? These are many of the commonly asked questions about acidity in wine.  Understanding acidity helps us to identify which wines we like and to better be able to pair wines with our favourite foods.

If you taste a wine that you find to be refreshing yet slightly tart, this is the result of dominant or prevalent acidity.  When someone says a wine is crisp, bright or fresh, it means the wine has great acidity.  Although these terms are most commonly referred to when discussing white wines, some red wines can be crisp, bright and fresh as well.

The common misconception is that some wines have acidity while others don’t, but all wines have acidity. Even in a wine such as Cabernet Sauvignon, which is normally thought of as deep and mellow, acidity helps blend all the other flavours of the wine. If a wine has no acidity at all, it tastes dull and flat. It is acidity that makes the wine appeal to your taste buds and enable you to recognize all the various flavours.

Acids are one of the four fundamental traits in wine; the others are tannin, alcohol and natural sugar. Acidity gives a wine its tartness. The amount of acidity varies depending on the type of wine.  Most range from 2.5 pH to about 4.5 pH on the acidity scale.  The lower the acidity the higher the pH level.

There are several different types of acids found in wine. The most prevalent acids are tartaric acid, malic acid and citric acid.  The amount of these acids in your wine will determine how much of a puckering sensation you experience in your mouth.

In wine tasting, “acidity” refers to the fresh, tart and sour elements of the wine which are evaluated in relation to how well the acidity balances out the sweetness and bitter components such as tannins.

The natural sugar content in a wine can disguise the acidity, making the wine seem smoother with a reduced puckering sensation.  An extreme example of this would be to compare the juice of a lemon with a glass of Coca-Cola.  Both have a pH acidity level of 2.5 but the intense puckering sensation of the lemon is not felt at all when you take a sip of the cola.

Acidity acts as a buffer to preserve the wine longer so high acid wines are more likely to improve with age. The stability of high acid/low pH wines helps during aging. Conversely, high pH wines are more prone to contamination. Microbes or other unstable components can make high pH wines appear hazy.

The type of acid present in a wine can also affect our perception of sourness and the puckering sensation. During the aging process, a wine’s malic acid is often converted to lactic acid, which results in a smoother, less tart-tasting wine.

Another facet of wine that can be confusing is a wine’s total acidity. This is something that’s often noted on a wine tech sheet or in the wine maker’s notes.  Total acidity tells us the concentration of acids present in wine, whereas the pH level tells us how intense those acids taste. For example, if you have a wine with 6 grams per litre total acidity and a pH of 3.2, it will taste more acidic than a wine with 4 grams per litre total acidity with the same pH level.

A higher acid white wine will be lemonier in flavour, making your mouth water and pucker a little.  Red wines with higher acidity are more likely to be a bright ruby colour, as the lower pH gives them a red hue. Higher pH, less-acidic red wines can take on a blue or purple hue. Wines with lower acidity can also take on a brown colour because they’re more prone to oxidation. It may not be as noticeable in red wines but can be off-putting in young white wines.

Unripe grapes have high acid levels that decreases as they ripen. Grapes grown in cooler climates usually contain higher acidity because there’s less warmth and sunshine available to increase grapes’ sugar and pH levels.

When pairing wine with food it’s helpful to consider the tastes found in a dish, whether it be sweet, sour, bitter, salty, fatty, etc. With a wine having a higher level of acidity, you’ll notice that sweetness, saltiness and fat balance the sour taste of the acidity.

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A wine barrel has become one of the most recognized symbols associated with wine. As a society we have romanced the wine barrel to the point where we have turned it into tables, benches, planters and candle holders.  Case in point, I have two barrels in my wine cellar as leg supports for a table and I have a candle holder made from a barrel rib on my bar.

The Romans discovered that oak could be more easily bent into the traditional barrel shape than palm wood; the oak only needed minimal toasting and a barrel could be created much faster. Oak was also the most abundant in the forests of continental Europe and its tight grain made it waterproof.

The Romans learned that oak has a tendency to soften and smooth the flavour of wine and provide it with a more complex taste.  Slight toasting of the wood added scents such as cloves, cinnamon, allspice or vanilla, as well as flavours such as caramel, vanilla or even butter.

Today wine barrels are made from a variety of materials; European oak (often referred to as French oak), American white oak, stainless steel, aluminum and HDPE (high-density polyethylene) plastic.  These barrels typically come in 3 standard sizes:

• Bordeaux type – 225 litres
• Burgundy type – 228 litres
• Cognac type – 300 litres.

Barrel aging is the main element of what is referred to as the élevage process, which is a French term meaning “raising” or “upbringing”. This is what occurs to the wine between fermentation and bottling.  The wine’s élevage can last for a few months to many years, during which time the wine’s flavours integrate and mature.

The winemakers’ choices during the aging process include how long to age the wine for and how much to manipulate it. which has a major impact on the taste of the finished product. One of the most important choices is what type of barrel to age the wine in.

When oak barrels are manufactured they are toasted over a fire to either a light, medium, or dark toast level. New barrels with a light toast will give lots of vanilla and caramel notes, while a darker toast will give smoky, roasted aromas.

An oak wine barrel’s age and size affect the amount of oak flavor that will be transmitted to the wine. Smaller barrels impart more oak flavor because they allow more contact between the wood and the wine. Oak barrels lose their flavour compounds with use so they must be replaced every few vintages.

In addition to adding oak flavours, new oak aging changes the tannin structure of red wines. Tannins from the wood barrel transfer into the wine, giving it a stronger structure. This contributes to a wine’s aging capability, or longevity in the bottle. The wood also helps stabilize the tannins from the grape skins, giving them a silkier texture.

After a few years of use, the oak will no longer provide flavour or tannin to the wine. The older barrels still allow for slow oxygenation, so they can be used to age wine that needs to mellow without the addition of oak flavouring.

Oak influences both red and white wines by adding the aroma of:

• Vanilla
• Caramel
• Baking spices like cinnamon, clove, nutmeg
• Coconut (especially from American oak)
• Dill (especially from American oak)

Red wines may also present additional aromas of:

• Smoke
• Chocolate
• Coffee
• Toffee
• Burnt sugar

Steel barrels, on the other hand, add no flavour to the wine.  Steel simply stores the wine for a few months while it stabilises and the grape flavours integrate. Steel barrels also don’t let any oxygen come into contact with the wine. This kind of aging helps wines retain the fresh fruit aromas that disappear when exposed to oxygen.

Stainless steel aging is used for wines that would not benefit from the addition of oak flavours or the softening effect that oak has on tannin. It is used for white wines not having tannins to manage. Stainless steel is the usual choice for aromatic and semi-aromatic white grapes including:

• Albariño
• Unoaked Chardonnay (often aged in oak as well)
• Gewürztraminer
• Grüner veltliner
• Pinot grigio
• Riesling
• Sauvignon blanc

For red wines, stainless steel is a good choice for lower tannin, fruity grapes such as:

• Baco Noir
• Gamay
• Grenache

Red wines aged in stainless steel are straightforward and juicy, with no oak flavours obscuring the flavours of the grapes.

Stainless steel aging is significantly less expensive than using oak because unlike oak barrels, steel barrels can be reused indefinitely and are much easier to clean. Stainless steel aging also takes less time than oak aging which saves winemakers crucial space in the wine cellar.

Since oak barrels can be used only two or three times for the purpose of adding flavour to the wine, the cost of buying new barrels is built into the higher prices of oak-aged wines. Some producers try to mimic the flavours of oak aging by adding less expensive oak chips to wines that are aged in stainless steel vessels. Oak chips add vanilla and spice notes but have no effect on a wine’s texture like oak barrels do.

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When a wine reviewer completes an assessment, the critic will describe the wine in terms relating to as many as 8 different components.  These include:

• Acidity
• Alcohol
• Anthocyanins (colour)
• Aromatic compounds
• Body
• Sweetness or Sugar
• Tannins
• Viscosity

Acidity

Acid is one of the most important elements in the pulp. As a grape ripens, its sugar content increases and its acid content decreases; the challenge is to harvest precisely when the optimal balance is struck.

Acid balances alcohol and sweetness and sometimes adds a crisp, refreshing sensation.  It may cause your mouth to pucker (like if you were biting into a lemon wedge). Grapes grown in cooler regions tend to have higher levels of acidity.

Alcohol

Alcohol is produced during fermentation when yeasts come in contact with the natural grape sugar in the grape pulp.  High-alcohol wines are full-bodied with a richer mouthfeel.  Alcohol generally has a sweet flavour.  A wine with high levels of alcohol sometimes gives off a hot, burning sensation that can be both smelled and tasted.

High levels of alcohol indicate that the grapes were very ripe at harvest.

Anthocyanins (colour)

Observing a wine’s colour can be a valuable clue for determining the vintage and assessing the wine’s quality.

Red wines lose colour as they age, becoming more garnet and eventually turning brown.  As much as 85% of anthocyanin is lost after 5 years of aging, even though the wine may still appear quite red.

Red wines that are more opaque generally contain higher levels of tannin, though Nebbiolo is an exception to this rule. 

There is reduced colour intensity when there is higher sulfite content.  Also, red wines fermented at higher temperatures will have reduced colour intensity.

The hue in red wine is partially affected by the pH level of the wine. There are many variables that will affect the colour but generally wines with a strong red hue have high acidity; wines with a strong violet hue have a mid-range of acidity; and those with a blueish tint (magenta) usually have a low amount of acidity.

White wines darken as they age, becoming a deeper gold or yellow and eventually turning brown.

Rosé wines are stained pink by macerating the skins of red grapes over an average period of 4 hours to 4 days.

Finally, oxidation in wine causes it to become brown in the same way as an apple browns that is left out on the kitchen counter too long.

Aroma

The aromas of wine are more diverse than its flavors. The human tongue is limited to the primary tastes perceived by taste receptors on the tongue – sourness, bitterness, saltiness, sweetness and savouriness.

The wide array of fruit, earthy, leathery, floral, herbal, mineral and woodsy flavours present in wine are derived from aroma or “nose” as it is often referred. In wine tasting, wine is sometimes smelled before being drunk in order to identify some components of the wine that may be present.

Different terms are used to describe what is being smelled. The most basic term is aroma which generally refers to a “pleasant” smell as opposed to odour which refers to an unpleasant smell or possible fault in the wine. The term aroma may be further distinguished from bouquet which generally refers to the smells that arise from the chemical reactions of fermentation and aging of the wine.

Body

It’s all about mouthfeel and weight.  The body of a wine is due to its alcohol content; however it also includes the perception of alcohol in a wine, associating with the balance of a wine.

• Light wine is often perceived and described as bright and acidic, fresh, citrusy and having fresh fruit notes.
• A medium bodied wine is one with lower alcohol levels, softer acids, little to no sugar content and little to no tannin.
• A fuller body wine is the result of several factors. Alcohol content creates viscosity, which adds to the fullness of the body. Tannins give wine structure, creating a thicker sensation in the mouth. Finally, sugar levels increase the viscosity of the wine, making it more syrupy and less watery.

Sweetness / Sugar

Sugar comes from ripe grapes (although some grape varieties naturally contain more sugar than others). It is mostly converted into alcohol during fermentation. Any remaining sugar is referred to as residual sugar.

A wine with high levels of residual sugar generally tastes sweet, has a richer mouthfeel and fuller body.  Grapes grown in warmer climates tend to get riper and contain more sugar.  Those wines having no apparent sweetness are referred to as being “dry”.

Tannins

Tannin belongs to a class of compounds called phenols and comes from grape skins and seeds; it is mostly found in red wines but can be found in some white wines.

Tannin is an important compound that plays a role in the aging of wine; therefore high-tannic red wines such as Cabernet Sauvignon and Nebbiolo are those that can be aged longest.

A good way to understand the effect of tannin is to think of a cup of hot tea in which the tea bag has steeped for too long.  The tea will taste very strong, harsh and rather bitter (tannic).  The flavour of the tea can be softened by the addition of milk. This same concept applies to wine, thus the reason why cheese and wine is a classic pairing.  The protein in cheese neutralizes or balances the tannins in wine.

Viscosity

Viscosity refers to the liquid consistency of wine. Viscosity will make the wine appear thin and watery, or may make it appear thick and syrupy.

Viscosity is affected by the levels of sugar and alcohol found in the wine. Generally speaking, the higher a wine’s levels of sugar and alcohol, the higher the wine’s viscosity will be.

Wines with high viscosity tend to cling to the side of a wine glass longer, and may leave “tears” or “legs” as the wine begin to slide back down into the glass.

Final Thoughts

Reviewer impressions are often very subjective and will reflect personal bias.  However, these descriptions and impressions are our best source for determining whether it is worth our while to invest in a particular wine or even a certain grape varietal.

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