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Acidity is one of the most important factors in wine. It affects its microbial, protein tartrate stability, malolactic fermentation, its color, flavor and aging potential of the wine. Adjusting the acidity is an important part of the winemaking process. The addition of acid to grape juice, must or wine will decrease the pH and increase TA of the wine. The low pH will make SO2 more effective against oxidation and bacterial infections, will increase the color intensity and ageing potential of the wine. The amount of acid needed to correct the acidity deficiency depends on the total acidity, the pH, and the buffer capacity of the juice, must or wine.
Addition of tartaric, malic and citric acids will affect the pH, TA and taste of the wine differently.
*1.0 g/L addition of Tartaric acid will increase the TA by about 1.0 g/L and will decrease the pH by 0.1 pH units.
*1.0 g/L addition of Malic acid will increase the TA by about 1.12 g/L and will decrease the pH by 0.08 pH units.
*1.0 g/L addition of Citric acid will increase the TA by about 1.17 g/L and will decrease the pH by 0.08 pH units.
Adding acid can result some precipitation of potassium tartrate (KHT) which will affect both pH and TA.
To avoid over adjustment, lab trial should be performed.
Deacidification is the process of reducing titratable acidity in grape juice, must or wine. The biological process of deacidification in wine is a malolactic fermentation, in which malic acid is converted to lactic acid and also softens the mouth feel of the acid. Physicochemical deacidification involves either acid precipitation or column ion exchange. The deacidification agents precipitate some tartaric acid in the form of insoluble salts.
Calcium Carbonate /CaCO3/ forms carbon dioxide and precipitates calcium tartrate (CaT). However, this introduces a risk of calcium tartrate instability. Simple deacidification with CaCO3 is used against high tartaric acid content, mainly on grape juice/must, also can be utilized on young wines as well. Be careful with CaCO3 additions. Excess calcium in the wine can cause ca-tartrate instabilities.
Potassium Bicarbonate /KHCO3/ and Potassium Carbonate /K2CO3/ are used for deacidification of grape juice, must or wine for improving quality or rounding off of flavors. They both form carbon dioxide and precipitate potassium bitartrate.
*With the double salt method you can reduce tartaric and malic acid. Double salt deacidification is a special technique in which you can take 20% to 30% of the volume to be treated and add all the CaCO3 calculated needed for the total volume. The goal is to precipitate tartaric and malic acid in roughly equal parts. The high pH over 4.5 produced in this fraction is to facilitate this.
To avoid over adjustment a lab trial should be performed.