The ‘Acidification’ is a winemaking process consisting of increasing the acidity in a grape must or wine. It is a legal and common practice in warm wine regions where grapes tend to lose acidity quickly before harvesting (while cool wine regions tend to enrich and/or chaptalize must or wine to compensate for the lack of grapes’ maturity). Unfortunately, it is often one of the only solutions left to winemakers wanting to make a balanced wine from grapes that reached full physiological ripeness but lost too much acidity in the process.
Why wine acidification is needed in warm wine regions
The fact that grapes tend to lose acidity too quickly in warm wine regions is due to the fact that in warm conditions, a large amount of the grape’s natural malic acid is degraded during the ripening process. As malic acid is way stronger (on the palate) than tartaric acid (also naturally present in grapes) and lactic acid (that generally appears during the malolactic conversion process – later on – during the winemaking process), its loss in a wine can be felt quickly.
The importance of a good level of acidity in a finished wine
A good level of acids (and therefore a low pH) not only improves the perceived freshness and fruitiness of many wines (which is a desired quality by wine consumers), but it also protects the wine against attack from bacteria. It also enhances the effectiveness of sulfur dioxide. It is to be noted that it can improve the colour of a finished wine.
Acidification regulations
Acidification is usually sanctioned by local wine regulations within carefully delineated limits in order to prevent the stretching of wine by adding sugar and water along with the permitted acid. Acidification is permitted in temperate zones like Bordeaux and Burgundy, with the reasonable restriction that no wine may be both acidified and enriched (it is either one or the other; it cannot both at the same time).
Regulations vary from country to country, but the most common permitted additives for acidification are, in descending order, Tartaric Acid, Citric Acid and Malic Acid.
Impact of the type of acid used to acidify
Tartaric Acid is often considered the acid of choice for adding to grape juice before fermentation because, unlike both citric acid and malic acid, Tartaric acid is rarely degraded during the fermentation process. Indeed, Citric acid and Malic acid can be attacked by the lactic acid bacteria during the fermentation process (that can happen spontaneously outside any malolactic conversion process initiated by the winemaker), which will consequently reduce the acidity level of the finished wine given that lactic acid is way softer on the palate than the other two.
Tartaric Acid and wine acidification
However, Tartaric acid is the most expensive of the three types of acids. Another disadvantage of the use of Tartaric acid is that most of it is precipitated as Tartrates inside a wine, forming little crystals inside the bottle (totally harmless to human health but wrongly considered by ordinary consumers as a wine default). Therefore, a cold stabilization of the finished wine may be needed before bottling to help remove these particles which can increase the cost of winemaking.
Malic Acid and wine acidification
Because of its high cost and microbiological instability, malic acid is rarely used to acidify.
Citric Acid and wine acidification
Citric acid is the least expensive of all tyhe types of acids that can be used to acidify a wine. However, it can quickly give an artificial taste to a finished wine. Furthermore, its use is not permitted in wines made or sold in the European Union. This is why citric acid is mostly used to make inexpensive wines. Additionally, it is mainly used at the final stages of the winemaking process for the producer to be able to control more precisely the flavour profile of his finished wine.
However, it is to be noted that the use of citric acid is allowed in many countries outside of the E.U. (including the U.S.). In these countries, citric acid is almost always used as a blending partner with other types of acids used to acidify wines or musts.
Additionally, one of the main advantages of citric acid is that it is not affected by the cold stabilization process.
Acidification timing
The timing of acid addition varies, but adding acid usually lowers pH so that an addition before or during fermentation results in better microbiological control of subsequent processes and favours the formation of desirable aromas in the finished wine. Fine tuning of acid levels can also take place at the final blending stage, but the drawback is that it is often very obvious in the finished wine, to the extent that it can be felt as artificial by wine consumers.
The main problem with Acidification
One of the most difficult aspects of acidification is determining how much acid to administer to achieve a desired final pH, in part because each wine or must has its own buffering capacity (see below).
Wine buffering capacity
The buffering capacity of a wine is the ability of a given wine to resist changes in pH when acids or bases are added. Each wine will react differently due to its individual characteristics. Consequently, two wines from a different region are susceptible to displaying a different pH despite having received the same level of acidification.
Acidulation
Acidulation is in fact just another term used to designate Acidification.
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