For all the wine geeks out there, we promised to talk about acids in wine and elaborate on their role and characteristics. So here we are.

Acidic wine makes you smile (Credit: Wyron A/unsplash.com)

Acids in Grapes

The primary organic acids in wine grapes are tartaric, malic, and citric acids. Tartaric acid, unique to grapes, is the dominant acid and can reach concentrations of up to 15 grams per liter in unripe grapes, typically found in musts at 3–6 grams per liter. Malic acid, common in green apples, occurs in grapes at 20 grams per liter before veraison, appearing in musts at 1–2 grams per liter in warm climates and 2–6 grams per liter in cooler climates. Citric acid is less abundant, at 0.5–1 gram per liter in grapes. During fermentation, acids like succinic, lactic, and acetic acids form, while ascorbic acid may be added for antioxidant protection. Other organic acids such as D-gluconic, mucic, coumaric, and coumaryl tartaric acids are also present.

Role of Acids in Wine

The role of acids is crucial as we have elaborated in one of our previous articles, but why is this like that?

It contributes to the common picture, which ultimately creates the taste, depending on alcohol levels, tannins, or sugars that are counterbalancing the acids in a wine.

Wine acidity plays a key role in its flavor, adding a sensation of freshness, its preservation, and overall profile. There are four primary types of acids found in wine: tartaric, malic, lactic and citric acid, each contributing uniquely to the wine's character.

Tartaric acid, the most abundant, is crucial for maintaining a wine's chemical stability and color. It imparts a crisp, fresh taste, especially prominent in grapes grown in cooler climates. Malic acid adds a sharp, green apple flavor, often softened in the winemaking process through malolactic fermentation, which converts it into milder lactic acid, enhancing smoothness and body. Citric acid, less common but impactful, offers additional freshness and a subtle citrus hint.

These acids are essential for balancing sweetness and bitterness, enhancing fruit flavors, and ensuring longevity by protecting against spoilage. Too much acidity can overwhelm the fruitiness, while too little may result in a flat, lifeless wine. Effective management of these acids can influence a wine's aging potential and sensory appeal, making acidity a critical component in winemaking.

Tartaric Acid

Tartaric acid is a key player in wine's acid profile, known for its robustness and ability to withstand alterations by other acids, earning it the nickname of a "fixed acid." Its stability is vital for preserving the color and flavor nuances of wine. The levels of tartaric acid in wine can vary significantly, influenced by the climate, soil conditions, and grape varieties used. Intriguingly, only about half of the tartaric acid found in grapes dissolves during the winemaking process, with the remainder binding to pulp debris, tannins, and pigments. Sometimes, this undissolved tartaric acid forms crystals known as "wine diamonds," which appear as tiny, shard-like crystals in the wine. These are harmless and indicate a natural aspect of wine's evolution.

Malic Acid

Malic acid is the second most abundant acid in wine grapes and plays a crucial role in the development of grapevines. Commonly found in fruits and berries, malic acid imparts a young, fruity character to the wine, often reminiscent of green apples. Its levels naturally decrease as grapevines mature, so the amount present in the wine largely depends on the grape variety. When malic acid levels are too high, winemakers often use malolactic fermentation (MLF) to convert malic acid into softer lactic acid, thereby smoothing out the wine's texture and flavor. This process is essential for creating balanced wines.

Lactic Acid

Lactic acid is primarily responsible for the buttery and creamy mouthfeel in wines, commonly found in fermented foods like yogurt and sourdough bread. During winemaking, winemakers can introduce lactic acid bacteria to convert harsher malic acid into lactic acid through malolactic fermentation (MLF). This process softens the wine, enhancing its complexity and imparting a smoother texture. While MLF can add desirable roundness to a wine's flavor profile, excessive lactic acid might contribute to headaches, especially in those sensitive to wine. Balancing lactic acid is crucial to maintaining the desired taste and texture without adverse effects on consumers.

Citric acid, also found in lemons, is not as prominent as other acids, but also plays a key role in wine. (Credit: Caroline Attwood, unsplash.com)

Citric Acid

Citric acid, while not as prominent as other acids, plays a key role in wine, too. Present in amounts about 1/20th that of tartaric acid, it is often added after fermentation to avoid yeast converting it to acetic acid. Citric acid contributes a sharp, tangy flavor and can enhance a wine's overall acidity, but it must be used cautiously due to its potency. Winemakers may use citric acid to fine-tune the acidity, ensuring the wine achieves the desired balance and brightness. Its judicious use can enhance the wine’s flavor profile without overpowering its natural character.

Beyond those four acids elaborated above the range of apparent acids is huge but bearing in mind their role is just a minor one.

Complexity or Wine Fault

Acetic acid, which is responsible for the vinegar taste, is generally considered a fault in wine, though a slight presence (known as volatile acidity or VA) is sometimes acceptable. A hint of VA can add complexity, but too much will spoil the wine, giving it a vinegar taste and eventually turning it into vinegar. Other acids such as gallic acid, often introduced during oak aging, and trace amounts of ascorbic, sorbic, and citramalic acids, contribute to the wine's complexity. These acids work together to produce various sensory experiences, from sharp and fresh to velvety and ripe, but can also cause undesirable flavors like rancid or sour if imbalanced.

Level of Acidity

The level of acidity in a wine depends on many aspects such as the grape variety, climate, date of harvest, yield, and whether the wine has been acidified or deacidified. Also, the aging of the wine can contribute to lower acid levels.

Finally, we come back to the point where acid levels have to be in balance with the other components in wine.

High residual sugar levels for instance in Trockenbeerenauslese do not mean a problem if you take into account that Riesling by nature is a high-acid grape variety contributing to the wine's overall freshness and balance.

We hope you got a little insight into the world of acids and your saliva is flowing already. We have put  a list of wines together, that will definitely make your mouth watering.

Go, and check them out.

Lotte Gabrovits

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