Determination of the acidity of the wort. Determination of titratable acidity of wort and wines. Preparing grapes for processing

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Acidity changes include acidification, or an increase in acidity, and deacidification, or a decrease in acidity. This issue was clarified at the ninth session of the International Organization of Vine and Wine (Faber, 1970).

Acidification. In some years, in some types of wines obtained in wine-growing regions with a hot climate, it is possible to correct the lack of acidity associated with very full maturation by introducing tartaric acid. EEC regulation provides for the possibility of acidification of pulp, grape must and young wines even during fermentation, depending on the zone. The limits of this addition of tartaric acid are given in table. 1.7.

Changing the acidity of the wort for different vineyards
Table 1.7

It is emphasized that acidification of the fortified wort and finished wine is prohibited. However, with regard to this last prohibition, the regulation is rather flexible in this respect, as it provides for deadlines. January 1 for viticulture zones C and March 16 for viticulture zones A and B. Therefore, it is quite clear that we are talking about finished wines, and not about new wine materials still in the process of fermentation. Moreover, there is no consensus on the question of when it is best to add tartaric acid (Amerin and Ug, 1970).
In areas with warm climates, such an addition is often necessary in order to obtain high quality, persistent wines with bright colors, pleasant taste and good preservation (Bremont, 1957). In temperate climates, deoxidation should be done much less frequently and even, as an exception, when it comes to fine and, in particular, red wines. Indeed, if the addition of tartaric acid makes it possible to obtain the best preservation of these wines, it is always at the expense of quality. As for red wines, the wines of the best brands are always velvety and full, with low acidity, and in this case, when tartaric acid is added, they become somewhat coarser and less velvety. White wines usually do the same and, apart from years of exceptional maturity, rarely require the addition of tartaric acid in these climates.
The best results for preserving the freshness of white wines are obtained by dressing them in such a way that it is better to preserve the entire amount of malic acid contained in them than to add tartaric acid to them. These observations are undoubtedly also valid for red table wines from the south of France. On the other hand, in the same area, some white wines, such as Clerette, often withstand a slight addition of tartaric acid.
In the Bordeaux region, careful blending of varieties almost always corrects any acidity deficiencies. Sometimes it would be possible to add tartaric acid salts to the Merlot or Semillon varieties, but their low acidity is compensated for by a higher
juicy acidity of Cabernet, Malbec or Sauvignon varieties cultivated in the same vineyard. In addition, since acidification is generally prohibited, the addition of tartaric acid is only permitted in exceptionally good years.
Although it is difficult to give any general recommendations for such a practice, it is still assumed that slight acidification can be performed if the total acidity in the wines is below 4 g / l. However, it is often more expedient to proceed from pH, in particular, at pH more than 3.6, acidification can be considered justified. Taking into account the precipitated fraction, it is believed that to restore the content of non-volatile acids after fermentation by 1 g / l, expressed in sulfuric acid, 200 g / hl of tartaric acid is needed. But the amount of tartaric acid should never be calculated in such a way as to bring the acidity to that of a normal wort. The addition of tartaric acid is carried out in much smaller doses (about 100 g / hl), which, without dissolving potassium, have a greater effect on the taste and active (true) acidity (i.e., slightly lower v pH) than on the titrated (total) acidity. Harvesting parts of the grapes before they are fully ripe or using small green clusters is a good natural acidifier.
It is pertinent to recall that the use of substances such as gypsum or calcium sulfate for acidification of grapes or must, which was once so praised in the south of France for lowering pH by replacing the tartaric acid anion (precipitated by calcium) with the sulfuric acid anion, is now completely discontinued. The addition of mineral acids: sulfuric, hydrochloric or phosphoric is strictly prohibited. Methods for increasing titratable acidity and lowering pH by means of cation exchange resins are currently prohibited in most wine-making countries, and in particular in France and other EEC countries. However, this process, which does not affect the concentration of organic acids in the wort, but only changes their ability to salt formation, is of certain interest. It is for this reason that the use of cation exchangers is the subject of research in a number of wine-making countries.
Finally, acidification with citric acid is not of interest, since the limit for total citric acid content of 1 g / l, established by the EEC Regulation, does not provide a noticeable increase in total acidity. It also requires very great care, at least in the production of red wines. In fact, citric acid is unstable from a microbiological point of view and can be degraded by malolactic bacteria with an increase in volatile acidity.

Deacidification... If a properly conducted wine preparation process can lead, especially for red wines, to a decrease in acidity mainly as a result of malolactic fermentation, then at the same time, these natural deoxidations can be insufficient or difficult to implement. In years of poor ripening grapes and in northern vineyards, you can apply the method of chemical deoxidation. Such deoxidation consists in neutralizing excess acidity in the wort by means of salt formation.
The regulation of the EEC established deoxidation limits depending on the viticultural zones (see table 1.7) and the products allowed for such
practice. Such products include potassium tartrate and calcium carbonate, the latter in some cases containing small amounts of the double calcium salt of D-tartaric and L-malic acids. Calcium tartrate and pure calcium carbonate act only on the percentage of tartaric acid, causing a slow precipitation of tartar or a more rapid precipitation of calcium tartrate.
Table 1.8 shows the analytical results of experiments carried out during the harvest in 1965 (Sudro and Lafit, 1967).
Table 1.8

To lower the acidity of the wort by 1 g / L (expressed in grams of sulfuric acid), 1 g / L of calcium carbonate or 2.5 to 3 g / L of potassium tartrate is required. The first product, which is more active due to its lower mass and better course of the reaction, is practically the only substance used for deoxidation. Under the action of wort acids, calcium carbonate decomposes, releasing carbon dioxide, and calcium forms acidic or neutral salts with tartaric acid (at pH 3.3, calcium in the acidic tartrate state is five times more than in the neutral state). Very little soluble neutral salt precipitates, and by shifting the equilibrium of the calcium non, a significant amount of tartaric acid precipitates. But calcium is never completely precipitated, and such enrichment with this cation creates a further risk of sedimentation in the bottles.
Although there are no precisely defined deoxidation limits, it can be considered that the EEC regulation indirectly sets one of such limits, specifying that table wine must have a total acidity of at least 4.5 g / l, expressed in tartaric acid (or 2.94 g / l, expressed in sulfuric acid). It seems that it would be better to take into account the content of non-volatile acids and even the content of residual tartaric acid. This applies to Austria, where the minimum content of tartaric acid is 0.5 g / l (Prillinger, 1967), and to France, where paragraph 5 of article 1 of the decree of November 23, 1967 establishes the minimum content of tartaric acid (0.99 g / l, or practically 1 g / l).
It is impractical to achieve a large decrease in acidity, which can reach from 2 to 3 g / l, since such deoxidation only due to tartaric acid would reduce its concentration by 3-4.5 g / l, i.e., it would remove the predominant part of this most important component wort. In the case of malolactic fermentation, such a strong decrease in the tartaric acid content will most likely lead to the fact that the wines will be low acidic, “flat” in taste. Therefore, it is recommended when calculating the dose of calcium carbonate to take into account the content of tartaric acid in the wort so that a sufficient amount of this acid remains, for example, 1.5 g / l.

For grapes with particularly high acidity in Germany, it was recommended (Wuherpfennig, 1967) to use double salt, tartrate and calcium malate for deoxidation (Münz, 1960, 1961), which is insoluble at pH more than 4.5. For this, a certain volume was taken from the total wort, which was completely neutralized with calcium carbonate containing small amounts of L-tartrate and L-calcium malate (Kilhofer and Würdig, 1963, 1964) with vigorous stirring. The precipitated double salt was filtered and the completely deoxidized liquid was mixed with the untreated part. To calculate the maximum deoxidation with double salts, a formula was derived (Rebelein, 1970) and tables were compiled to calculate the amount of wort used in this deoxidation method (Hausgofer, 1971, 1972).
In most cases, grape deacidification should be considered not as a simple chemical correction, but as a means to initiate a chain of natural wine deoxidation processes: first, precipitation of potassium bitartrate, then carrying out malolactic fermentation or biological deoxidation. Under these conditions, the addition of calcium carbonate at a rate of 50 to 75 g / hl, and in exceptional cases 100 g / hl, is sufficient to obtain, especially in red winemaking, biologically stable wines.
Oenologists disagree on the best time to perform deoxidation. Deoxidation experiments carried out in Switzerland (Michaud, 1958; Michaud and Fell, 1960) and carried out both before and shortly after the completion of alcoholic fermentation, show that the same final values \u200b\u200bof the content of tartaric acid, potassium and total acidity are obtained, and the same pH value provided that such deoxidation is carried out before the start of malolactic fermentation. A desire was also expressed to expand the possibility of using deoxidation and wine (Negr, 1958). However, in order to create more favorable conditions for malolactic fermentation, deoxidation must be carried out quite early, still in the pulp or in the wort. When making wine using the red method, good results are usually achieved by deoxidizing when the still warm wine comes out of the vat during fermentation. At this stage of wine preparation, it is easier to obtain a fairly accurate value of its final acidity than to make calculations based on the composition of the wort, and, in addition, mixing the liquid with calcium carbonate is facilitated by the absence of pulp. This practice is fully consistent with the EEC regulation, which sets the same limits for deoxidation as given above for acidification.
It should also be noted that other neutralizing substances: sodium carbonate, potassium carbonate, magnesium carbonate, caustic soda and caustic potash are strictly prohibited. They usually give poor organoleptic results due to their harsher action and also impart a salty flavor to the wine.
Finally, it should be noted that the EEC regulation allows deacidification of concentrated musts regardless of the region of their origin and prohibits acidification and deacidification on the same product.

Most fruit juices contain too much acid and too little sugar. Without must stabilization, the wine is very sour and not strong enough. Only some grape and apple juices do not need to be corrected, in other cases the intervention of the winemaker cannot be done. There are methods to normalize acidity and sugar content, minimally affecting the organoleptic properties of wine.

You can determine the initial acidity of the juice with a special device - "pH meter" or by reference tables of the acid and sugar content in fruits. It is advisable to use data from your region. Average data are given in tables.

Wines with 4-6 grams of acid per liter are considered balanced. During fermentation, the concentration drops, so the initial acidity of the wort is made higher - 6-15 grams per liter.

Sometimes, for example, in pear juice, it is necessary to increase the acidity of the wort. The easiest way to do this is by adding the right amount of citric acid (juice). The juice of one lemon contains 4-5 grams of acid.

Methods to lower the acidity of wine

Attention! It is necessary to reduce the acidity before or during fermentation (with the exception of settling in the cold), working with the must, and not the finished wine.

1. Dilution with water. The most common method used by almost all home winemakers. One drawback is that the wine extract decreases, as a result the drink loses some of its aroma and taste.

Water reduces the acidity of the juice by half. It is important to take into account the added sugar. After dissolving, 1 kg of sugar increases the volume of the wort by 0.6 liters, reducing the acidity in the same proportion as water.

Let's say there is juice with an acidity of 18 grams per liter and a sugar content of 8%. If we want to reduce the acid content to 6 g / l, we need to dilute it three times (18: 6 \u003d 3), that is, add 2 liters of water to 1 liter of juice. But the acid concentration also falls due to the added sugar, so its volume must be subtracted from the calculated amount of water.

1 gram of fermented sugar (natural and added) gives 0.6% alcohol in wine. To obtain wine with a strength of 12%, a total of 200 g / l of sugar is required. In the example, the volume of wort is planned to be 3 liters; to obtain a given strength, 600 grams of sugar are required. At the same time, 80 grams is in the juice itself, which means that another 520 grams (600-80) must be added during fermentation. This sugar will take up a volume of 0.312 L (520 × 0.6). We reduce the amount of water by this volume (2-0.312 \u003d 1.688 l).

Therefore, to make wine with a strength of 12% and an acidity of 0.6%, you need to add 520 grams of sugar and 1.688 liters of water to the juice with the initially specified parameters. At first, the calculations seem complicated, in fact, if you understand the essence, everything is simple.

2. Blending of juices. The idea is to mix the acidic juice in certain proportions with another non-acidic juice, equalizing the overall acidity of the wort. It is advisable to mix juices of the same fruit, but different varieties. For example, grape with grape (red with red), apple with apple, etc. If the fruits are different, in most cases the wine will not taste good.

Unlike adding water, mixing juices does not reduce flavor intensity; it is the best method to lower acidity, but it is rarely used in home winemaking, since it is difficult to find a suitable material for blending.

3. Adding acid absorbers. Adding substances to the wort that neutralize the acid. It can be special powder chemicals (used according to the instructions) or folk remedies: chalk, gypsum and eggshells.

First, the shell is washed, the film covering the egg from the inside is removed, then crumbled into small pieces. Chalk and plaster can be put in whole or previously crushed. Part of the wine material is poured into a separate container and mixed with a quencher. It takes 1 gram of chalk or eggshell to neutralize 1 gram of acid. When a precipitate has formed, the reduced acidity juice is added to the main wort (no precipitate). The disadvantage of this method is that after neutralization, an unpleasant odor may appear.

4. Cold. When the temperature drops to 2-4 ° C, acid salts precipitate. The method is used both for must and for finished wine, with its help it is possible to reduce the acidity by 1-1.5 g / l, which is very little. Cold can only fix wines with a slight excess of acid.

5. Boiling. The high temperature lowers the acidity of the wine, but this method has a number of disadvantages, including: folding of proteins (reduced extractability), the appearance of a “boiled” taste, loss of aroma, and yeast death. Because of this, boiling is almost never used.

Titratable acidity above 0.90 tends to disturb the balance of the wine, making it taste too sour. Some whites, such as Champagne or Ravat 51, affected by Botrytis, may have slightly higher acid levels, but 0.90 is the upper limit for high quality, balanced wines, both white and red. One might think that the increased titratable acidity is somehow related to the pH level of the wort or wine, since the pH level also measures acidity. In fact, pH is the negative logarithm of positively charged hydrogen ions, while titratable acidity measures the acid content of wort or wine by weight. The titratable acidity does not correlate perfectly with the pH level. In Washington state, for example, growers often produce grapes with high acidity and high pH levels.

Tartaric acid, dissolving in a liquid, is much faster and easier than malic acid, splits into positively and negatively charged hydrogen ions, and that is why it has a stronger and sharper taste.

Unbound hydrogen ions are essentially atomic traps that are just waiting for something to gobble up in the chemical sense of the word. This implies both the human palate and the tongue, it is because of the presence of unbound hydrogen ions that our tongue defines wine as sour, too sour, and you quickly spit it out.

If you add tartaric acid to a low-acid wort, you will also lower the pH on the acid scale to an unpredictable level. Penn State University Robert Byluff mentioned wines with poor aroma, faded color, high pH (4.0), which could be brought down to pH 3.4 by adding tartaric acid and then cryo-stabilized. He also claims that this wine then won third place in a national competition.

Correction of titratable acidity With tartaric acid it also has a positive effect at higher pH levels, lowering it, but the purpose of the correction is titratable acidity, not the pH level. If the titratable acidity is normal and the pH is slightly elevated. an experienced winemaker is unlikely to fuss about it. The titratable acidity is ten times more important for the taste of the wine than the pH level, so it is the titratable acidity that needs to be adjusted first, and the pH level adjusts itself. While we don't really focus on adjusting the pH level, you still need to know it in order to assess its effect on the quality and taste of wine, as well as to know exactly how much potassium metabisulfite to add. After you have corrected the titratable acidity with tartaric acid, you need to re-measure the pH level, it will have a different value.

Wines with a pH below 3.0 are difficult to ferment, and when they do begin to ferment, the fermentation process takes longer. These wines have such a level of acidity that wine enzymes are practically unable to act. Wines with a pH of 4.0 or more have a rather poor and unsaturated taste, lacking in freshness and juiciness. They are also susceptible to damage by disease-causing organisms that prefer to exist in an environment close to neutral. The pH level of 3.5 inhibits the growth of almost all disease causing microbes. It is for this reason that some oenologists claim that the maximum pH for any wine is 3.5. PH scale: 14.0 most alkaline 7.0 neutral 4.0 - acidic.

A more acidic pH can have the following effects: When the pH rises to 3.5, the wine turns purple or purple; at pH below 3.5, the color of the wine is red, characteristic of the claret. Wine connoisseurs and connoisseurs believe that ruby \u200b\u200btones of wine are preferable to purple tones. According to scientific research, connoisseurs have every reason to associate wine color with quality, as wines with a pH of 3.5 or below have a higher aroma class than wines with a high pH. It is the color component, anthocyanin, that most affects the aroma of red wine.

Also, as we have already seen, a lower pH is more effective for potassium metabisulphite as more sulfur dioxide is retained in an unbound, active state. At a pH of 4.0, virtually all of the sulfur dioxide is converted to bisulfite ions. High pH wines are also more susceptible to oxidation, which degrades the quality of the aroma and darkens both white and red wines with a slightly brownish tint. Finally, red wines with a pH less than 3.3 are resistant to lactic acid fermentation.

The pH of the wort increases during the fermentation process. “A wort with a pH of 3.2 to 3.4 produces a finished wine with a pH of 3.6 to 3.8,” says Bouloff, “So I would say a pH between 3.1 and 3.2 ideal level for white wine must. The ideal wort pH for red wine is approximately 3.4 ".

We have already found that the pH level must be taken into account when determining the date of harvest (and this will happen on the same day you crush the grapes). So you will most likely have a wort with ideal pH values, or as close to ideal as the rest of the titratable acidity and Brie allow. It is still useful to check the pH level of the finished wort so that you have all the correct information.

To determine the acidity of the wine as accurately as possible, you have to "conjure" a little. Armed with a burette, pipette, litmus paper and special titration liquid, you will get a fairly accurate result. In addition, after carrying out some simple manipulations, you will know exactly how much sugar you need next time to get the drink of the acid you need.

To make good wine, it is important that the juice has a certain acidity. Juice that is acidic enough ferments better, reducing the risk of mold and harmful bacteria. The acidity of wine is considered normal in the range from 6 to 10%.

The determination of the acidity of juice is based on the property of acids to combine with alkalis. Consequently, the acidity of the juice can be determined by the amount of alkali that was required to neutralize the acid.

The process of determining the acidity of juice is called titration (from "titer" - the amount of alkali in 1 ml of solution) and consists in adding an alkali solution of a certain concentration - a titrated solution to the juice.

As a rule, sodium hydroxide solution is used as this agent. The end of the reaction is determined by litmus paper, which turns red in acid, and turns blue in alkali.

How to determine the acidity of wine wort at home

Before determining the acidity of wine at home, prepare the following inventory:

a 10 ml pipette;
burette - a glass tube with a glass cock with a volume of up to 50 ml, on which divisions are applied corresponding to a volume of 0.1 ml; for convenience, the burette should be positioned vertically (preferably with a tripod);
a porcelain cup;
glass rod;
titration liquid, that is, 5.97 g of dry sodium hydroxide dissolved in 1 liter of distilled water, with a volume of 0.25 liters (store in a glass bottle with a ground stopper);
litmus test.

The process of how to determine the acidity of the must for wine is as follows. The titration liquid is poured into a clean, dry burette. Then the valve is opened to release the air from the burette. This must be done, otherwise the result will be incorrect. The upper liquid level is set at the zero division of the burette. After that, the pipette is filled with juice to zero graduation (10 ml) and poured into a cup.

Since fruit and berry juices are highly colored, they are pre-diluted with distilled water (at the rate of 20–50 ml per 10 ml of juice) and stirred well. If not, you can use plain water, but boiled 4-6 times. The fact that the juice is diluted with water does not affect its acidity at all. In the diluted juice, the same amount of acid remains, it just becomes less colored, which makes it much easier to get the result.

After that, place a cup with diluted juice under the burette, carefully open the tap and release 1 drop of an alkaline solution. The contents of the cup are thoroughly mixed with a glass rod and the juice is applied to litmus paper with it. If it remains red, the acid has not yet been neutralized. Another drop of an alkaline solution is dropped into the cup and the contents are checked again with a litmus paper, and so on until the litmus paper turns blue, that is, until all the acid combines with the alkali. It is known that 1 ml of alkali corresponds to 0.1% acid in juice.

In addition, the wine must contain acid - about 6-7 g per 1 liter. You can reduce acidity by adding water even before fermentation, in fruit juice.

The acidity of wine is determined by the content of titratable acid in grams per liter of wine (ppm) and can range from 2.5 to 9 g / l.

It should be remembered that the acidity of light wines can be 5.5–7 g / l of acid in 1 l, table wines - from 7 to 9 g / l, dessert - 9-11 g / l.

One of the main indicators of the chemical composition and taste of wine is acidity. Distinguish between titratable, volatile and active (pH) acidity.

Titratable acidity -The sum of acids and their acidic salts contained in wort and wine, which are titrated with an alkali solution until the pH is brought to 7.0. The content of acids neutralized by alkali is expressed in terms of tartaric acid in grams per dm3. For different groups of wines, titratable acidity is allowed within the following limits (g / dm3):

Still wines 3-8

Sparkling red wines 5-7

Sparkling white wines, including champagne 6-8.5

Volatile acidity – An indicator characterizing the health of wine materials. Therefore, during their aging or storage, a periodic chemical analysis of the wine is carried out. Volatile acidity increases with wine oxidation and as a result of microbial diseases. The state with the industry standard of Ukraine (GSTU 202.002-96) allows the following maximum value of this indicator (in g / dm3):

For ordinary white dining rooms - 1.2; in pink - 1.3;

For ordinary red dining rooms - 1.5; vintage - 1.3;

For fortified reds and Madeira - 1.2; for whites - 1.0 g / dm3.

The increased volatile acidity of the wine can be corrected by re-fermenting the diseased wine with fresh grape must. The content of volatile acids in wine is determined by the method of distillation with steam and the method of fractional distillation. The steam stripping method is arbitration. Volatile acids are removed from the wine using water vapor in a special device. The resulting distillate with 0.1 N sodium hydroxide (NaOH) solution in the presence of phenorl-phthalein indicator.

Active acidity (true acidity - negative logarithm) concentration of hydrogen ions; expressed by the pH symbol and is the most accurate characterization of the acidity of wort and wine.

Active acidity depends on the content of the strongest acids, which have the highest acid dissociation constant (K). So, in decreasing degree of acidity of wine are located: Lemon(K \u003d 8.4 10-4), Amber(K \u003d 7.4 10-5), Apple(K \u003d 3.95 10-4), Dairy(K \u003d 1.4 10-4). As you can see, lactic acid has a dissociation constant, and therefore in its solutions the highest negative logarithm of the concentration of hydrogen ions and this has a positive effect on the taste of wine.

There is no relationship between active acidity and titratable acidity. Thus, two wine samples with the same titratable acidity may have different pH values. The relationship between pH and acidity of the medium is clearly visible in the following diagram:

The pH value determines the quantitative ratio of primary and secondary fermentation products, the tendency of wine to oxidation, to metal classes, crystalline and biological opacities, the course of wine pasting, and even the value of the RH potential.

The active acidity of must and wine fluctuates on average in the range of pH 2.8 - 3.8, however, in wines from the southern regions of viticulture, the pH value reaches 4.6, which forces the wine to be acidified with citric acid. In Italy and France, mass table wines of the southern and northern regions are specially blended together.

At high pH, \u200b\u200bwines are easily affected by bacterial diseases and are more susceptible to oxidation; there are metal cash desks and processing with bentonite becomes difficult; medium salts of tartaric acid (tartar) precipitate more intensively, and the color intensity of wines decreases.

To increase the pH of the wine, chalking is used. This is called deacidification of highly acidic wines:

Tartaric lime.

This technique should not be used for high-quality wines, but nevertheless it allows you to weaken the acidity in unfavorable conditions of grape ripening, opens up the possibility of the passage of YMB processes.

It is extremely beneficial for Spanish winemaking Low acid wort gypsum: The grapes entering the sherry production are sprinkled with a certain amount of gypsum. Free tartaric acid is formed:

Gypsum - potassium bitartrate - tartaric acid - tartaric acid

As a result, the titratable acidity almost does not change, but the active acidity increases markedly - the pH value decreases. This is due to the fact that the amount of hydrogen ions in the wort increases due to an increase in tartaric acid (VCC), as well as due to the formation of acidic potassium sulfate with an increased dissociation constant:

In addition, gypsum prevents the acid salts of tartaric acid from precipitating, which is usually observed during fermentation and alcoholization of wort.

In connection with the plastering, the wines become fresher in taste, with a more lively color and acquire greater resistance to diseases. Gypsum is added in an amount of 1.5-2 g per 1 kg of pulp. It is believed that it is gypsum that gives sherry wines the highly valued salty taste.

To lower the pH by 0.1 add 1.9 g / dm3 citric acid and 2.27 g / dm3 tartaric acid. Measure the active acidity of the wine using a pH meter.

Distinguish between low acid and high acid wines. Lack of acidity makes the taste simple, flat; increased - leads to a sharp, rough sour taste. Each type of wine must have its own optimal acidity. Champagne wine materials are the freshest in taste; increased acidity is also necessary for young table wines. A tingling acidity is characteristic of sparkling wines, unkind and freshly fermented wort, which has fermentation carbon dioxide. Wine materials made from unripe grapes with an excess of malic acid are distinguished by the unpleasant so-called "green acidity". The hard "metallic" sour taste is due to the increased content of mineral acids that occurs after excessive sulfitation of the wines. The mild acidity in the taste of aged wines is explained by the content of bound acids (mono- and disubstituted salts, acidic esters).