Have you heard the term wine acidity? How does it play a role in wine flavor? Let's find out together!

Wine acidity meaning

Wine acidity meaning

There are four basic elements of wine including tannins, alcohol content, sweetness and acidity. Wine acidity is an important ingredient in both the production of the wine and the final product of the wine. They are found in both grapes and wine, which directly affect the color, balance and flavor of the wine as well as the growth and vitality of the yeast during fermentation and protects the wine from bacteria.

The measurement of the amount of wine acidity is called "titratable acidity" or "total acidity" refers to the test that obtains the total number of acids present in wine, while the strength of the acid is measured in terms of pH with most wines having a pH between 2.9 and 3.9. In general, the lower the pH, the higher the acidity in the alcohol. However, there is no direct relationship between total acidity and pH (high pH wine can be found for wines and high acidity).

During the wine tasting, the term "acidity" refers to the fresh and sour properties of wine as assessed in relation to the balance between the acidity and bitter components of a wine such as tannins. Three main acids are found in wine grapes: Tartaric acid, malic acid and citric acid. During winemaking and final product, acetic, butyric, lactic and succinic acids can play important roles. 

Most of the acids associated with wine are stable acids with the notable exception of acetic acid, which is mainly found in vinegar and can contribute to wine defects known as easy acidity evaporation. Sometimes, additional acids such as ascorbic acid, sorbic acid and sulfuric acid are used in winemaking.

Tartaric acid

Tartaric acid

This is the most important substance in alcohol due to its prominent role in maintaining the stability of the wine, the color of the wine and ultimately affecting the flavor of the finished wine. In most plants, this organic acid is rare, but it is found in significant concentrations in vines. Along with malic acid, tartaric is one of the fixed acids found in wine grapes. The concentration varies depending on the variety and the soil content of the vineyard. 

About red wine acidity, some varieties, such as Palomino, are naturally processed to have high tartaric acid content, while least acidic wine types such as Malbec and Pinot noir are typically lower. During flowering, high levels of tartaric acid are concentrated in grape flowers and then on young fruit. As the vine ripens, tartaric is not metabolized by respiration like malic acid so tartaric acid levels in grapes remain consistent throughout ripening.

Less than half of tartaric acid found in grapes is in the free state, with most of the present concentration being the potassium acid salt. During fermentation, these tartrates bind to lees, pulp fragments, tannins and precipitated pigments. Although there are some differences between grape varieties and winemaking regions, in general, about half of the residue is soluble in the alcohol mix. 

Crystallization of these tartrates can occur at unpredictable times. In wine bottles can, they look like broken glass, despite the fact they are harmless. Winemakers will typically pass the wine through cold stabilization, where it is exposed to temperatures below freezing to encourage the tartrate to crystallize and precipitate out of the alcohol or electrolysis to remove the tartrate through a membrane process.

Malic acid

Malic acid

Riesling from wine regions with cool climates, such as Rheingau in Germany will have more malic acid and green apple notes than wines from warmer regions. Malic acid along with tartaric acid is one of the main organic acids found in wine grapes. It is found in most fruit trees and berries but is most often associated with green apples. Its name comes from the Latin word malum meaning "apple". In grapes, malic acid is involved in a number of processes that are essential to the health and sustainability of the vine. Its chemical structure allows it to participate in energy-transporting enzyme reactions throughout the vine.

Its concentration varies depending on the variety, with some varieties, such as Barbera, Carignan and Sylvaner being processed naturally at high levels. Malic acid concentrations in grapes peaked just before veraison, when they can be found at concentrations as high as 20 g / l. As the vine progresses through ripening, malic acid is metabolized during respiration. When harvested, its concentration can be as low as 1 to 9 g / l. Respiratory malic acid loss is more pronounced in warmer climates. When all malic acid is used up in a grape, it is considered "overripe" or old. Winemakers must compensate for this loss by adding foreign acids to the winery in a process known as acidification.

Malic acid can be further reduced during alcohol production through malolactic or MLF fermentation. During this process, the bacteria convert the stronger malic acid into softer lactic acid. Formally, malic acid is polyprotic (contributes 2 protons) while lactic acid is monoprotic (contributes one proton) and therefore has an only half the effect on acidity (pH). In addition, the first acid constant (pK a) of malic acid (3,4 at room temperature) was lower than the acid constant of lactic acid (3.86 at room temperature), indicating a stronger acidity. So, after MLF, wine has a higher pH (less acid) and other palatability.

The bacteria behind this process can be found naturally in the winery, where the oak barrels will contain a colony of bacteria or they can be introduced by the winemaker to a specimen transplant. For some wines, converting malic to lactic acid can be beneficial, especially if the wine has an excess of malic acid. As for other wines, such as Chenin blanc and Riesling, it produces flavors in the wine (such as the buttery scent of diacetyl) that won't appeal to that variety. In general, red wine is more often passed through the MLF than white wine, meaning that the likelihood of finding malic acid in white wine is higher (although notable exceptions such as Chardonnay are often included).

Lactic acid

Lactic acid

This is a much lighter acid than tartaric and malic. Lactic acid is often associated with the "milk" flavor in wine and is the main acid of yogurt and sauerkraut. It is produced during wine production by lactic acid bacteria (LAB), which consists of three genera: Oenococcus, Pediococcus and Lactobacillus. These bacteria convert both sugar and malic acid to lactic acid then through the MLF. This process can be beneficial for some wines, adds complexity and softens the acridness of malic acid, but it can create flavors and turbidity in others. Certain LAB strains can produce biogenicamin, such as histamine, tyramine and putrescine.

This is a known cause of red wine headaches in some alcohol drinkers. Wine manufacturers who want to control or prevent MLF can use sulfur dioxide to stun bacteria. Winemakers must also be very careful with the barrels and winemaking equipment in which alcohol comes into contact with alcohol, because of the potential for bacteria to penetrate deep into the wood fibers. A completed barrel of wine on a successful malolactic fermentation will almost always produce MLF in every wine stored in it ever since.

Citric acid

Citric acid

Citric acid is very common in citrus fruits, such as limes. Citric acid is found only in very small amounts in wine grapes. It usually has a concentration of about 1/20 compared to tartaric acid. The most commonly citric acid in wine is a commercially produced acid supplement derived from a solution of sucrose. These inexpensive supplements can be used by alcohol manufacturers during the acidification process to increase the total acidity of alcohol. It is used less often than tartaric and malic due to the strong citric flavor it can add to alcohol. 

When adding citric acid, it is always done after the primary alcohol fermentation has been completed due to the yeast's tendency to convert citric to acetic acid. In the European Union, the use of citric acid for acidification is prohibited, but limited use of citric acid is permitted to remove excess iron and copper from alcohol if potassium ferrocyanide is not available.

The importance of wine acidity level

In winemaking

In winemaking

The highest acidity in winemaking grapes is achieved just before the onset of veraison, opening up the 9-cycle course of the annual vine cycle. As grapes ripen, their sugar content increases and their acidity decreases. Through respiration, malic acid is metabolized by the vine. Grapes from cooler climates usually have a higher degree of acidity due to a slower ripening process. The level of acid remaining in the grapes is an important consideration for winemakers when deciding when to start harvesting. 

For wines like Champagne and other sparkling wines, having a high acidity is even more important to the winemaking process. Therefore, grapes are usually picked when they are unripe and at a higher acidity level.

During the winemaking process, the aiding acid enhances the effectiveness of sulfur dioxide to protect the alcohol from damage and can also protect the alcohol from bacteria due to the inability of most bacteria to survive in the low pH solution. Two notable exceptions are Acetobacter and lactic acid bacteria. In red wine, the acidity helps preserve and stabilize the wine's color. 

The ionization of anthocyanins is affected by pH, so wines with lower pH (such as wines based on Sangiovese) have a more stable color. Wines with a higher pH (such as wines based on Syrah) have a higher level of less stable green pigment, which eventually turns a dull gray. These wines can also turn brown. In white wine, a higher pH (lower acidity) causes the phenol in the wine to darken and eventually polymerize as a brown residue.

Winemakers will sometimes add acid to wine to make the wine more acidic, most commonly in warm climates where grapes are typically harvested at advanced ripening stages with high sugar content but very low acidity. Tartaric acid is often added but winemakers will sometimes add citric or malic acid. Acid can be added before or after primary fermentation. They can be added during blending or brewing but the increased acidity becomes more noticeable to the taster if added at this time.

In wine tasting

In wine tasting

Wine acidity is an important ingredient in the quality of wine. It adds sharpness to the taste. In addition, it is most easily detected with a stinging sensation on the sides of the tongue and a palate aftertaste. Of particular importance is the balance between the acidity versus the sweetness of the wine (residual sugar content) and the more bitter components of the alcohol (most notably tannins but also other phenols). Alcohol that is too acidic will have an overly sour and sharp taste. Wines with too little acid will have a bland taste with a less definitive flavor.

How to pair food and wine to balance wine acidity

How to pair food and wine to balance wine acidity

When combining food with wine, you need to pay attention to the flavors in the dish (sweet, sour, bitter, salty, fatty ). The goal is to create a basic food concept for you to choose from. When caring about acids in wine, you must also pay attention to the balance of sweetness, salinity and fat. This is why Champagne and French fries are so suitable to be enjoyed together (acid + fatty and salt is a good pairing).

How to reduce wine acidity

There are three ways to reduce wine acidity to get it right

Dilution

Dilution

If the wine is too tart, you can add more water to dilute the alcohol. You should use distilled water so that free oxygen from the water is not included in your alcohol. The obvious problem with using this method to reduce alcohol acidity is to dilute the flavor of the wine. If you've used the wine acidity test kit and know-how acidic your wine is and how much it should be, you can use Pearson's Square to find out how much water is needed to reach the target acid level.

Neutral

Neutral

A perfect product to reduce wine's acidity is the Acid Reducing Crystal. It is added directly to alcohol and partially neutralizes the acid making it tartrate crystals. The instructions on the side of the bottle will tell you the exact amount of Acid Reducing Crystals to add to reach your target acid level.

Malolactic fermentation

Malolactic fermentation

Malolactic fermentation is essentially a controlled bacterial fermentation with the culture of selected malolactic bacteria. It is separate from alcohol fermentation and is usually initiated at the end of yeast fermentation. The malolactic medium slowly ferments malic acid to both lactic acid and CO2. Lactic acid does not taste as acidic as malic. Half of the lactic acid is released from alcohol as CO2. Some wines are usually malolactic fermented for flavor consideration but not all wines are suitable for malolactic fermentation. 

For this reason, you should use malolactic fermentation with caution when used with the sole purpose of reducing wine acidity.

The final thought

Hopefully, the above article has provided you with a basic understanding of wine acidity and its importance to wine. You can also measure and reduce wine acidity in the ways that our article has shared.